Phase 4 Science Report Final

GVI Costa Rica Expedition 062 Report (Phase 4) 10th April – 18th June 2006

GVI Costa Rica Expedition 062 (Phase 4) Report 10th April – 18th June 2006 Submitted in whole to: Global Vision International COTERC Steven Furino, Waterloo University, Canada Submitted in part to: The Ministry of Environment and Energy of Costa Rica (MINAE). 26th June 2006 Produced by Britt Larsen, Expedition Leader Lydia Chaparro, Science Officer Nicole Evans, Community Liaison Officer James Lewis, Science Officer Julie Jackson, Intern Alec Gibbson, Intern And Ariane Tempier Anthony Schultz Brian Jenkins Joanna Banks Suzanne Byrne Emma Stillmann Angus Davidson Sunil Sharma James Guilder Alexander Horn Lisa Unsworth Kevin Middleton Dominic Greves

Caitlin Reynolds Elliott Woodward Katie Huskey Kelly Ammon Mary Wagner Megan Behles Natalie Perini Sarah Itoh Tiffany Burtch

Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member Expedition Member

GVI Costa Rica Address: Estación Biológica Caño Palma, Tortuguero, Costa Rica Tel: (+506) 709 8052 Email: [email protected] & [email protected]

Webpage:http://www.gvi.co.uk

1.

EXECUTIVE SUMMARY

The fourth 10-week phase of the Costa Rican Global Vision Internal (GVI) Expedition has now been completed. The expedition has maintained working relationships with local communities through both English classes and Inter-cambio. The expedition has continued to work towards the gathering of important environmental scientific data whilst working with local, national and international partners. The following projects have been run during Phase 4: •

Jaguar predation on sea turtles. In collaboration with the Costa Rica Ministry of Environment and Energy (MINAE)

•

Marine

Turtle

Monitoring

Programme

(collaboration

with

the

Canadian

Organization for Tropical Education and Rainforest Conservation (COTERC), MINAE and the Caribbean Conservation Corporation (CCC)) •

EBCP Resident Bird Project (collaboration with Steven Furino, Waterloo University, Canada)

•

Tourist impact assessment within the Tortuguero National Park

•

English language lessons (collaboration with the San Francisco community)

•

Inter-cambio with staff from Cabinas Vista al Mar and the Tortuguero National Park staff at Cuatro Esquinas

•

Tourist impact assessment on Caño Palma canal in addition to and in comparison with the tourist impact assessment conducted in Tortuguero National Park

1.1.

Introduction

The Coastal Rainforest Conservation Expedition at the Biological Station Caño Palma in Tortuguero, Costa Rica has now completed its fourth phase (4 x 10 weeks). The expedition to date has assisted in collecting a substantial amount of scientific data. Although this data is already helping to identify potential future research areas and providing important data to the national and international scientific community it is still at the preliminary stage. Methodologies continue to be improved and focused as experience is gained and improvement to data quality is continuous. A full Annual Report in (to be initiated in December 2006) will collate and summarize all data and enable more descriptive and accurate analysis.

i

Contents 1.

EXECUTIVE SUMMARY .......................................................................................i 1.1.

Introduction....................................................................................................i

Contents ...................................................................................................................ii Tables..................................................................................................................... vii Figures................................................................................................................... viii 2.

3.

JAGUAR PREDATION ON MARINE TURTLES.................................................10 2.1.

Introduction.................................................................................................10

2.2.

Aim .............................................................................................................11

2.3.

Methodology ...............................................................................................11

2.4.

Results .......................................................................................................12

2.5.

Discussion ..................................................................................................14

MARINE TURTLE MONITORING PROGRAMME..............................................16 3.1.

Introduction.................................................................................................16

3.2.

Aim .............................................................................................................17

3.3.

Methodology ...............................................................................................17

3.3.1.

Study site............................................................................................17

3.3.2.

Daily track census and nest surveys ..................................................18

3.3.3.

Night surveys......................................................................................19

3.3.4.

Tagging...............................................................................................20

3.3.5.

Biometric Data ....................................................................................20

ii

3.3.6.

Turtle disease or injuries ....................................................................21

3.3.7.

Nest Survivorship and Hatchling success ..........................................21

3.3.8.

Physical Data......................................................................................21

3.3.9.

Human impact data ............................................................................21

3.4.

Results .......................................................................................................22

3.4.1.

Daily track census and nest surveys ..................................................22

3.4.2.

Monitoring of nests .............................................................................24

3.4.3.

Monitoring of female turtles ................................................................25

3.4.4.

Tagging...............................................................................................26

3.4.5.

Biometric data.....................................................................................27

3.4.6.

Turtle disease or injuries ....................................................................29

3.4.7.

Nest survivorship and hatchling success............................................30

3.4.8.

Human impact data ............................................................................30

3.5.

Discussion ..................................................................................................31

3.5.1.

Daily track census and nest surveys ..................................................31

3.5.2.

Monitoring of nests .............................................................................31

3.5.3.

Monitoring of female turtles ................................................................33

3.5.4.

Tagging...............................................................................................33

3.5.5.

Biometric data.....................................................................................33

3.5.6.

Turtle disease or injuries ....................................................................34

3.5.7.

Nest suvivorship and hatchling success.............................................34

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3.5.8. 4.

EBCP RESIDENT BIRD PROJECT....................................................................36 4.1.

Introduction.................................................................................................36

4.2.

Aim .............................................................................................................37

4.3.

Method .......................................................................................................37

4.3.1.

Point Counts .......................................................................................37

4.3.2.

Area Searches....................................................................................38

4.3.3.

Incidental Observations ......................................................................39

4.4.

Results .......................................................................................................40

4.4.1.

Survey Data........................................................................................40

4.4.2.

Incidental Observations ......................................................................44

4.5. 5.

Human Impact Data............................................................................35

Discussion ..................................................................................................45

NATIONAL PARK TOURIST IMPACT ASSESSMENT ......................................47 5.1.

Introduction.................................................................................................47

5.2.

Aims ...........................................................................................................50

5.3.

Methods......................................................................................................50

5.3.1.

Aquatic Trails......................................................................................50

5.3.2.

Terrestrial Trail ...................................................................................52

5.3.3.

Strawberry Poison Dart Frog transects ..............................................52

5.3.4.

Assessment of visitor use of aquatic trails within the National Park ...53

5.3.5.

Assessment of terrestrial trail condition ..............................................53

iv

5.4.

5.4.1.

Aquatic Trails......................................................................................54

5.4.2.

Terrestrial Trail ...................................................................................58

5.4.3.

Strawberry Poison Dart Frog (Dendrobates pumilio) Transects .........59

5.4.4.

Assessment of visitor use of aquatic trails within the National Park ...59

5.4.5.

Assessment of terrestrial trail condition ..............................................61

5.5.

6.

Results .......................................................................................................54

Discussion ..................................................................................................61

5.5.1.

Aquatic Trails......................................................................................61

5.5.2.

Terrestrial Trails..................................................................................65

5.5.3.

Strawberry Poison Dart Frog Transects .............................................66

5.5.4.

Assessment of visitor use of aquatic trails within the National Park ...66

5.5.5.

Assessment of terrestrial trail condition ..............................................67

5.5.6.

Summary included in report to National Park .....................................67

TOURIST IMPACT SURVEY CAÑO PALMA .....................................................68 6.1.

Introduction.................................................................................................68

6.2.

Aims ...........................................................................................................68

6.3.

Methods......................................................................................................69

6.3.1.

Aquatic Trails......................................................................................69

6.3.2.

Boat Dock Survey...............................................................................69

6.4.

Results .......................................................................................................70

6.4.1.

Aquatic Trails......................................................................................70

v

6.4.2. 6.5.

7.

Boat Dock Survey...............................................................................70

Discussion ..................................................................................................70

6.5.1.

Aquatic Trails......................................................................................70

6.5.2.

Boat Dock Survey...............................................................................71

COMMUNITY WORK..........................................................................................71 7.1.

Introduction.................................................................................................71

7.2.

Aims ...........................................................................................................71

7.3.

Method .......................................................................................................72

7.3.1.

Expedition Member training................................................................72

7.3.2.

Teaching.............................................................................................72

7.4.

Results .......................................................................................................73

7.5.

Discussion ..................................................................................................73

8.

Bibliography ........................................................................................................74

9.

APPENDIX..........................................................................................................78

vi

Tables Table 3-1. Number of nests, half moons and horizontal distribution of nests from the North Beach…………………………………………………………………………………22 Table 3-2. Tags applied by Caño Palma Sea Turtle Monitoring Programme from 1st March to 15th June 2006…………………………………………………………………...26 Table 3-3. Leatherback mean carapace length, carapace width and clutch size on the North Beach…………………………………………………………………………………27 Table 3-4. Green mean carapace length, carapace width and clutch size on the North Beach………………………………………………………………………………………..28 Table 3-5. Hawksbill mean carapace length, carapace width and clutch size on the North Beach…………………………………………………………………………………28 Table 3-6. Loggerhead mean carapace length, carapace width and clutch size on the North Beach…………………………………………………………………………………29 Table 3-7. Mean and range carapace length and width and clutch size of leatherback turtles found more than once on the North Beach………………………………………29 Table 4-1. Incidental recordings of rare species observed during phase 4………….44 Table 5-1 Number of the most common key species observed during each study phase based on Caño location……………………………………………………………54 Table 5-2 Adjusted number of the most common key species observed during each study phase based on Caño location…………………………………………………….55 Table 5-3 Records collected from night survey of the terrestrial trial during phase 4………………………………………………………………………………………………59 Table 5-4 Data collected during Phase 4 on the total number of boats recorded entering Tortuguero National Park………………………………………………………..60

vii

Figures Figure 2-1. Beach distribution of Jaguar tracks, turtle tracks, and dead turtles along the 14.5 miles in Tortuguero National Park. …………………………………………….13 Figure 2-2. Date distribution of Jaguar tracks, dead turtles, and total turtle tracks in Tortuguero National Park………………………………………………………………….14 Figure 3-1. A) Seasonal nesting distribution of leatherback turtles. B) Seasonal nesting distribution of green, hawksbill and loggerhead turtles on the North Beach………………………………………………………………………………………...23 Figure 3-2. A) Spatial nesting distribution of leatherback turtles. B) Spatial nesting distribution of green, hawksbill and loggerhead turtles on the North Beach…………23 Figure 3-3. Destiny of the nests (all species) on the North Beach……………………24 Figure 3-4. Temporal activity distribution of the 4 studied species (error bars 5%) on the North Beach…………………………………………………………………………….25 Figure 3-5. Nesting orientation of the 4 studied species (n = 27) on the North Beach between March 1st and June 15th 2006…………………………………………………..26 Figure 3-6. Distribution of the injuries presents on the turtles checked on the North Beach………………………………………………………………………………………...30 Figure 4-1. Distrubution of survey periods and study sites during Phase 4………….40 Figure 4-2. Key species recorded during surveys of the Cleared Areas study site……………………………………………………………………………………………41 Figure 4-3. Key species recorded during surveys of the Caño Palma study site……42 Figure 4-4. Key species recorded during surveys of the Cerro Tortuguero study site……………………………………………………………………………………………43 Figure 4-5. Key species recorded during surveys of the North Beach study site……44

viii

Figure 5-1. Variation in most common key species recorded based on study phase in all Caños…………………………………………………………………………………….56 Figure 5-2. Variation in most common key species recorded based on study phase and Access (AC) Caño only……………………………………………………………….57 Figure 5-3 Variation in most common key species recorded based on study phase and Caño (Harold (CH) and Chiquero (CC) only)………………………………………57 Figure 5-4 Variation in observed records of Little Blue Heron (Egreta Caerulea) based on study phase within all study areas…………………………………………….58 Figure 5-5 Data collected during Phase 4 on the total number of tourist boats recorded entering the National Park……………………………………………………...60 Figure 5-6 Data collected during Phase 4 on the total number boats recorded entering the National Park…………………………………………………………………61 Figure 6-1. Key species recorded during surveys of the Caño Palma study site……70

ix

2.

JAGUAR PREDATION ON MARINE TURTLES

2.1.

Introduction

Tortuguero National Park (TNP) is the most important nesting ground in the western hemisphere for Green Turtles (Chelonia mydas). In addition to the Green Turtles there are also a significant number of Leatherbacks (Dermochelys coriacea) and the occasional Hawksbill (Eretmochelys imbricata) and Loggerhead (Caretta caretta) (Troëng, 2000). The nesting turtle population has been monitored on the beach of the park since the 1950’s and continues to be monitored today by the Caribbean Conservation Corporation (CCC). The National Park is also home to the Jaguar (Panthera onca) which is the largest felid in the western hemisphere (Silver et al., 2004) measuring up to two meters in length and weighing about 120 kg. The Jaguar population is threatened in main due to hunting, habitat destruction and fragmentation. This fragmentation can result in populations becoming so isolated they are considered severely endangered (Madellin et al., in press). The range of Jaguars stretches from southern USA to Argentinean Patagonia and has been reduced by 50% since 1900 (Sanderson et al., 2002).

The range of an

individual Jaguar is estimated to be as low as 1 individual per 11km2 (Silver et al., 2004) to as high as 1 individual per 64km2 (Rabinowitz & Nottingham, 1986). Jaguar preys on a variety of species including White-lipped Peccary (Dicotyles pecari), White-tailed Deer (Odocoileus virginianus), Baird’s Tapir (Tapirus bairdii), Capybara (Hydrochaeris hydrochaeris), turtles, and Spectacled Caimen (Caiman crocodiles) (Oliveira, 1994). Information on Jaguar predating on sea turtle is sparse. In TNP, and many other areas, marine turtle predation by Jaguar has been recorded sporadically. Eighty-two C. mydas were identified as being predated by Jaguar in Suriname from 1963-1973. On the same beach in 1980 one Jaguar killed 13 turtles within only a few days (Autar, 1994). On the Pacific coast of Costa Rica Jaguar have been recorded preying upon Olive Ridley Turtles (Lepidochelys olivacea), Black Turtles (Chelonia agassizii), and Hawksbills E. imbricate. This predation upon turtles by Jaguar is not a new phenomenon but seems to have been increasing in the past 10 years within TNP (Troëng, 2000; Magally Castro, pers. comm.). Although, there has been much research done on turtles in TNP from 1956 to 1995 there were only two C. mydas’s recorded to be killed by Jaguar (in 1981 and 1984) (Carrillo et al., 1994). Weekly walks on the beach to record the number of 10

dead turtles killed by Jaguar began in 1997, as part of the turtle monitoring programme, and continued until 1999. Four dead C. mydas were found killed by Jaguar in 1997, 25 in 1998, 22 in 1999, and two Leatherbacks in 1999 (Troëng, 2000). Though there is much more to learn about the predation of Jaguar on marine turtles some interesting data has been collected to date. Jaguars have been recorded killing marine turtles in the open area of the beach and occasionally dragging the turtle to the vegetation. There was one instance where a turtle was dragged 100 meters into the forest. In most cases a very small proportion of the turtle was eaten, in many examples only the neck muscle was consumed (Troëng, 2000). Troëng (2000) also states that there was evidence of Jaguar approaching nesting turtles yet not attacking them. Theories for this behaviour were not put forward, however ongoing field work undertaken by GVI may help to gain an understanding of Jaguar prey selection within TNP. Due to a lack of human resources the Costa Rican Ministry of Environment and Energy (MINAE) invited GVI to continue data collection on Jaguar presence and predation of marine turtles in TNP. Data collection has now been conducted by GVI since 11 July 2005. Together with the data previously collected by MINAE, a more comprehensive understanding of Jaguar impact on the turtle population of TNP can be developed. 2.2.

Aim

The Jaguar project aims to document the presence of Jaguar on the beach of Tortuguero National Park and their predation of nesting marine turtles. 2.3.

Methodology

Jaguar surveys are conducted over the 14½ mile stretch of beach from the entrance of Tortuguero National Park (mile 3½) south to Jalova lagoon (mile 18). At least four surveyors conduct the survey once per week, starting from either Tortuguero or Jalova at dawn. General data such as date, name of researchers, weather, sand condition and start time is noted at the beginning of the survey. Beach size (distance from vegetation to high tide mark) is recorded every four miles (at mile 4, 8, 12 and 16) to give an indication of how much beach was exposed during the previous night. Sand condition and general weather are also recorded every four miles.

11

During the survey, researchers count the total number of fresh (1-2 nights old) turtle tracks on the beach, including both half moons (not nested) and full tracks (nested). It should be noted that during the peek of C. mydas season these numbers cannot be exact because of the high numbers of turtle tracks that are seen on the beach. When fresh Jaguar tracks are encountered, the right hind foot is photographed and the length and width of the track are measured. The direction of the track (north or south) and location (mile marker and GPS coordinates) are also recorded. The track is then followed until it ends (goes into the vegetation or is washed away by the tide) and the mile marker and GPS coordinates are recorded again. As would be expected intense and prolonged rain, high winds and very dry sand, can reduce the quality of Jaguar prints making data collection very difficult. As weather conditions vary throughout the year it is possible data quality will be affected. In order to minimise this Jaguar surveys are undertaken during and after periods of optimal weather conditions when possible. Data is also collected on fresh carcasses of turtles killed by Jaguars. This includes location (mile marker and GPS coordinates), species, point of attack, number of nights since kill, amount of meat eaten, location of carcass relative to the vegetation, whether the turtle is on its front or back, and any extra comments/observations. Photographs of particular features may be taken. 2.4.

Results

A total of 9 full surveys were conducted between 19 April and 14 June with an average time of 8 hours and 6 minutes. A total of 40 surveys have been conducted by GVI since 11 July 2005. During Phase 4, 18 C. mydas were killed by Jaguars. The number of separate sets of Jaguar tracks found during this phase was 35. A total of 455 C. mydas tracks and 170 D. coriacea tracks were recorded in eight of the nine surveys 1.

1 1

There was no distinction made between Green and Leatherback tracks on one Jaguar survey.

12

50 T otal Jaguar T racks T otal T urtle T racks Dead T urtles

45 40 35 30 25 20 15 10 5

18 M

ile

17 ile M

M

ile

16

15 M

ile

14 M

ile

13 M

ile M

ile

12

11 M

ile

10 ile M

M

ile

9

8 ile M

M

ile

7

6 ile M

ile M

M

ile

4

5

0

M ile M arker

Figure 2-1. Beach distribution of Jaguar tracks, turtle tracks, and dead turtles along the 14.5 miles in Tortuguero National Park. Period: 19 April—14 June 2006.

During this phase, all of the turtle carcasses were located between miles 6 ½ and 15 with a high concentration between miles 10 and 13 ½. The area between miles 9 and 10 ½ contained 4 turtle carcasses and the area between miles 12 ½ and 14 contained 6 turtle carcasses. The highest concentration of Jaguar tracks was between miles 9 and 10 ½ and again between miles 12 ½ and 14. The turtle carcasses found within the high Jaguar activity area make up 56% of the total turtle carcasses found. Figure 2-1 shows the location of turtle tracks, Jaguar tracks, and turtle carcasses per half mile. Figure 2-2 shows the number of turtle tracks, Jaguar tracks, and turtle carcasses for each walk.

13

10

180 P.onca Tracks Dead Turtles Turtle Tracks

160

8

140

7 120 6 100 5 80 4

Number of turtle tracks

Number of P.onca tracks and number of dead turtles

9

60 3 40

2

20

1

0

0 Wk 1 (19/04/06)

Wk 2 (26/04/06)

Wk 3 (03/05/06)

Wk 4 (10/05/06)

Wk 5 (19/05/06)

Wk 6 (24/05/06)

Wk 7 (31/05/06)

Wk 8 (07/06/06)

Wk 9 (14/06/06)

Figure 2-2. Date distribution of Jaguar tracks, dead turtles, and total turtle tracks in Tortuguero National Park. Period: 19 April—14 June 2006.

2.5.

Discussion

Data collected during Phase 4 from mid-April to mid-June includes part of the D. coriacea season and the beginning of the C. mydas season. D. coriacea and C. mydas tracks were seen on all walks throughout the phase. All 18 dead turtles found were C. mydas. The kills that were recent were always found near Jaguar tracks and many of the turtle carcasses were found in high Jaguar activity areas. All of the turtle carcasses were found between miles 6 ½ and 15 which could in part be due to the fact that there is less human presence in this area.. All 18 C. mydas carcasses found were presumed to be killed by Jaguar.

Most of the

turtles were found in the vegetation having been dragged by the Jaguar from the beach. This varies from the findings of the patrols done from 1997 to 1999 when most turtles 14

found were in the open area. One potential reason for this is that there may be more people walking the beach now forcing the Jaguars to retreat into the vegetation. However, the surveys conducted in the past were focused mainly on recording turtle tracks. Therefore the team may have missed some turtles that were located in the vegetation whereas the main focus of the GVI surveys is to record how many turtles are being predated on by Jaguar each year. Because of this there is a conscious effort by the team to walk very close to the vegetation to avoid missing any dead turtles. Supporting previously collected data the fresh kills show that only a small part of the turtles are eaten by Jaguars including the neck muscles and part of the internal organs. It is not known why Jaguars kill turtles and then eat only a small amount. However, one theory put forward is that turtles may be used as training for young Jaguars since they are easy to approach and kill (Schaller, 1972). It may also be that Jaguars exert such a small amount of energy killing turtles that not much meat is required to replace the total energy expenditure of the kill. There were many other potential Jaguar prey seen on the beach during the surveys, such as a White-nosed Coati (Nasua narica), Black River Turtle (Rhinoclemmys funerea), Spider monkeys (Ateles geoffroyi), Green Iguanas (Iguana iguana), Great Curassows (Crax rubra), Red Brocket Deer (Mazama Americana), and a species of opossum. Therefore Jaguars may be on the beach in search of any prey species and not turtles exclusively. Further research on this topic is needed before any conclusions can be made. The last walk of Phase 4 occurred on the 14th of June which is only the beginning of the C. mydas season. From January 2006 to the last walk in June there have been a total of 20 recorded dead turtles killed by Jaguar. It is assumed that over the next three or four months, until the end of C. mydas season, more turtles killed by Jaguar will be found. The number of turtle carcasses will most likely be significantly higher than the numbers found in 1998 and 1999. Only 25 C. mydas were killed in all of 1998 and 22 killed in all of 1999. There is much speculation as to why the numbers of turtles killed by Jaguar are increasing and it could be due to a combination of factors. The Jaguar population could possibly be increasing in the Park, pushing more Jaguars onto the beach in search of prey. The habitat destruction of surrounding areas for banana plantations and cattle ranches could be forcing Jaguars to move towards the coast. It is also possible that there is a decline in other prey species causing Jaguar to prey upon turtles out of necessity (Troëng, 2000). 15

In all surveys, pictures and measurements were taken of the back right print of the Jaguar. The intention was to be able to identify individual Jaguar’s through a computer program that analyses 48 different measurements (Miller, 2001).

It has since been

confirmed that distinction of Jaguar using this program is not possible (C. Miller, pers. comm.) Surveys will continue to be conducted throughout the C. mydas season allowing for a better analysis of an entire year which will provide much valuable data on the predation of marine turtles by Jaguars. This data will help to continue improving the monitoring project and will provide a useful tool for the management and conservation of Jaguars and turtles in Tortuguero National Park.

3. 3.1.

MARINE TURTLE MONITORING PROGRAMME Introduction

Over the past 20 years there has been a huge decline in both Leatherback Turtles (Dermochelys coriacea) (Troëng et al., 2004) and Green Turtles (Chelonia mydas) (Troëng & Ranking, 2005) due to overexploitation such as illegal harvesting of their meat and eggs, as well as fishing, contamination and habitat alteration. The D. coriacea is classified as critically endangered and C. mydas as globally endangered on the IUCN Red List (IUCN, 2003). In addition to the general decline in sea turtles, Tortuguero and the surrounding areas are continuously developing and thus the demand for protection and conservation of the sea turtles and their habitat is growing. Tortuguero National Park (TNP) was established in 1975 with the main purpose of protecting sea turtles and the nearby areas of humid lowland forest and beach (A. Castro, pers. comm.). While this protection is contributing to the stability of sea turtle populations, many beaches surrounding the park are supposedly undergoing a high percentage of poaching (J. Daigle, pers. comm.). In response to this, COTERC (Canadian Organization for Tropical Education and Rainforest Conservation) started a five-year long feasibility study in 2004 with the aim of determining nesting populations and poaching rates of C. mydas and D. coriacea on North Beach (the beach just north of

16

Laguna Tortuguero) and occasionally Hawksbill (Eretmochelys imbricata) and Loggerhead Turtle (Caretta caretta). In July 2005 GVI joined COTERC in collecting data on the unprotected North Beach. As well as collaborating on the data collection and analysis, GVI and COTERC shared data with the CCC (Caribbean Conservation Corporation) in order to gain more knowledge from tagged turtles and compare poaching rates of turtles nesting on protected National Park beaches. 3.2.

Aim

According to previous studies (conducted by COTERC) there is a great amount of illegal harvesting of turtle eggs, and to a lesser extent turtle meat, on the North Beach. Thus, the aim of this project is to study the spatial and seasonal distribution of nesting females, the number of mature females, illegal harvesting of turtle meat and eggs, and natural predation of nests. Through these means the project aims to study, monitor and protect the sea turtles coming to nest on the North Beach, as well as compare the data with other important nesting sites like the TNP. 3.3.

Methodology

The methodology used for the marine turtle monitoring program follows the COTERC and GVI protocol which is adapted from and approved by the CCC. 3.3.1.

Study site

The North Beach, which encompasses the study area, is 3 1/8 miles long (5 kilometers) and extends from the Tortuguero river mouth (10º36’36,9”N - 83º31’52,1”W) at the most southern point until Laguna Cuatro (10º37’56,3”N – 83º32’25,7”W) in the north. Although this beach is not within the TNP boundaries, it is situated within the Barra Colorado Wildlife Refuge which, like the TNP, also is managed by ACTo (Area de Conservación Tortuguero) under MINAE – the Costa Rican Ministry of Environment and Energy). The study area begins at Mile 0 just north of Tortuguero river mouth (10º35’51”N – 83º31’40”W) and extends to Laguna Cuatro, at Mile 3 1/8. The entire study area is divided and marked with mile markers each 1/8 of a mile (200 meters) from the south to 17

the north with ascending numbers. This allows for the documentation of spatial distribution and density of nests along the beach. The nearest village to the study beach is San Francisco, situated south of mile 0, a constantly growing community of about 100 residents. Two hotels (Cabinas Vista al Mar and Turtle Beach Lodge) and a few ranchos and houses are built along the study beach. On the southern side of Tortuguero river mouth is Tortuguero beach where the CCC monitors from mile 0 (10º35’51”N – 83º31’40”W) to mile 18 (10º21’46”N – 83º23’41”W) at Jalova lagoon. The sand of the study beach is black and fine with a typical high energy-beach. The width of the nesting beach platform (or berm) vary from 2 to 38 meters, but the configuration of the shape and size of the berm changes constantly in response to long shore drift and exposure levels. The dominant plants on the nesting beach are plants such as the morning glory family (Ipomoea Pes-Caprae), Rea-purslane (Sesuvium portulacastrum), and Rush grass (Sporobolus virginicus). The berm is bordered by a hedgerow of Cocoplum (Chrysobalanus icaco) and Sea grapes (Coccoloba uvifera) with a mixture of Coconut palms (Cocos nucifera) and various tropical hardwoods behind. The beach is littered with a variety of debris including logs, coconuts husks and a large amount of plastics, trash, beer bottles etc... 3.3.2.

Daily track census and nest surveys

The turtles found in this area are D. coriacea, nesting from March to mid-July, C. Mydas, nesting from June to November, and occasionally E. imbricata and C. caretta, nesting from June to September (Troëng et al., 2004). Because of this our surveys were conducted every day and night from March to June and will continue through November 2006. In between GVI expedition phases COTERC alone conducts all surveys. The daily track surveys began every day at 6:00 am and finished by 7:30 am and consisted of walking the beach between mile 0 and 3 1/8, recording and monitoring the tracks and nests from the night before. The day team identified tracks as full (turtle nested), half moon (non-nesting emergences in which the track takes the form of a 18

parabolic curve), or a lifted turtle (no tracks going back into the sea). The vertical position of the nest on the beach was identified either as Open (O – area of beach which receives 100% sunlight), Border (B - area where nest is partially shaded by vegetation) or Vegetation (V - area where nest is constantly shaded by vegetation). Nests are then identified as natural (if remained in its original state), predated by an animal or poached (with signs of stick marks, exposed egg chamber, eggs shells on the sand or human foot prints). Data was also recorded when encountering dead turtles on the beach. The size, sex, state of turtle, and an estimated time of death were recorded. Any obvious signs of an unnatural death are also recorded such as harpoon marks, machete cuts or blows to the head and/or limbs and photographs are taken. If the turtle has been tagged, the ID number was recorded and checked against CCC tagging data. 3.3.3.

Night surveys

Each night there is a survey consisting of walking the beach between mile 0 and 3 1/8 during 5 hours (21:00 to 02:00) and since 5 June the night surveys where divided in 2 shifts (20:30 to 00:30 and 00:00 to 04:00). The purpose of the night patrols is to collect data from as many turtles as possible. However, considering that the beach is 3 1/8 miles in length and only one night team goes out at the same time (except between 00:00 and 00:30 where 2 teams meet), there was a high possibility that not all turtles were observed while nesting at night. When this happened their tracks were documented by confirming that there were two sets of tracks (one ascending and one descending the beach). In this case the methodology used was the same for the day protocol. When encountering a turtle on the beach, the following data was collected: The date, the time that the track was encountered and the species. The initials of each member of the team, as well as mile marker number and GPS of each nest, were recorded every time. The position of the nesting turtle (turtle facing North, South, East or West) and the vertical position of the nest in the beach (Open, Border or Vegetation) were recorded. If the nesting process was observed, a count of the number of eggs (and for D. coriacea also the yolkless eggs) was recorded. Any other comments or anomalies observed were also noted. 19

3.3.4.

Tagging

D. coriacea females were tagged on the membrane located between the tail and rear flipper using Monel #49 tags (National Band & Tag Co., Newport, USA). The C. Mydas, E. imbricata and C. caretta females were tagged in the front flippers just before the primary scale using Inconel #681 tags. Females were only tagged after having completed the nesting process, while they were covering the nest or returning to the ocean. Evidence of old tags in the flippers, old tag notches (OTN) or old tag holes (OTH), was also recorded, as well as evidence of trauma or parasites due to old tags. 3.3.5.

Biometric Data

During the oviposition process clutch size (number of eggs) was recorded by hand (using a plastic glove) and a manual counter (clicker). In Leatherbacks clutch sizes includes fertile and infertile eggs. For all turtles found after the oviposition process, the Minimum Curved Carapace Length and the Maximum Curved Carapace Width were recorded by two people using a 300 cm fibreglass measuring tape. The measurement was reviewed three times to allow for precision and the average of the three measurements was used as the final measurement. •

Minimum Curved Carapace Length (CCLmin): In Leatherbacks CCLmin is measured from the beginning of the carapace, extending along the side of the central dorsal ridge, until the tip of the caudal projection. For the three other species the measurement was taken exactly along the center of the carapace.

•

Maximum Curved Carapace Width (CCWmax): Measured at the widest part of the carapace from one side to the other.

Deformation or missing pieces of the carapace and flippers or any other relevant data were also recorded.

20

3.3.6. Turtle disease or injuries Fibropapilloma tumours, deformation or missing pieces of the carapace and flippers, as well as any other relevant data was also recorded inspecting the turtle, after the oviposition process, using a flashlight with a red light. 3.3.7. Nest Survivorship and Hatchling success Samples of nests were marked using triangulation in order to locate the nest at estimated hatchling time. During oviposition triangulation was conducted using three pieces of flagging tape (tags) which were attached to vegetation behind the nest. The distance from the centre of the egg chamber to each of these tags was measured, to the nearest cm, whilst the turtle was still laying eggs. The distance to the most recent high tide line was also recorded. When it was time to excavate the nest, the triangulation allows finding the location of the egg chamber at the site where the three tag lines crossed. Three tags were used to compensate for the loss of any tapes. If one tag was lost it was still possible to locate the nest using the other two tags. 3.3.8.

Physical Data

The ambient temperature as well as rainfall and relative humidity were taken on the beach at 6:00 a.m. and 6:00 p.m. on a daily basis. The ambient temperature and relative humidity were recorded with a handheld Skymaster device and rainfall was recorded from a rain gauge positioned at Cabinas Vista al Mar, on the upper platform of the beach, with a PVC tube (8.5 cm × 160 cm). 3.3.9.

Human impact data

Due to the recent increase in human activity on the North Beach all artificial light (white or red) observed during the night surveys were recorded. As well as the number of people, fires and tourist with or without guide.

21

3.4.

Results

Data was collected from 1st March to 15th June, covering 3 of the 4 months of the Leatherback Turtle nesting season. The total number of morning and night surveys was 108 and 107, respectively. During the daily track census a total of 668 6/8 miles (321 hours) was walked, taking an average of 1 hour and 30 minutes to complete the 3 1/8 miles of the beach. Meanwhile, the nightly surveys covered 878 miles (507.5 hours), taking an average of 4.78 hours to walk an average of 9 miles per night. 3.4.1.

Daily track census and nest surveys

Without taking into consideration the half moons, lifted or dead turtles, 59% (n=44) of the turtles that came onto the beach to nest were seen during the nights patrols. The remaining 41% were from tracks found but no turtle seen, 14% (n=10) of which were observed during nights patrols and 27% (n=20) during the daily track census. Only 4 turtles were observed doing a half moon. The tracks encountered on the North Beach were identified as leatherback, green, hawksbill and loggerhead turtles. A total of 103 tracks were observed, divided into 71 nests and 32 half moons. The nests were 73% Leatherback (n=52), 17% Green (n=12), 7% Hawksbill (n=5) and finally, 3% were Loggerheads (n=2). The horizontal distribution of these nests on the beach was 76% in the open area (n=54), 17% in the border (n=12) and 7% in the vegetation (n=5). See details in table 3-1.

Specie

Nest

Half moon

Horizontal distribution of the nests Open

Border

Vegetation 0

Leatherback

52

21

47

5

Green

12

10

4

4

4

Hawksbill

5

1

1

3

1

Loggerhead

2

0

2

0

0

Total

71

32

54

12

5

Table 3-1. Number of nests, half moons and horizontal distribution of nests from the North Beach between March 1st and June 15th 2006.

The first sea turtle activity recorded was a Leatherback half moon the 2nd March, but the first nest was not until the 5th March. The first green turtle nest and half moon were 22

recorded the night of the 23rd April, and for the Hawksbill and Loggerhead the first nests recorded were on the 26th April and the 26th May, respectively. The seasonal distribution (from March 1rst to June 15th) of leatherback turtles nesting on the North Beach is shown in figure 3-1 A. Figure 1-1 B shows the distribution for the rest of the species. See Appendix A for a more detailed figure. The nights with maximum of activity recorded were the 17th May (3 Leatherback and 1 Green nests, plus 2 Green half moons), the 12th June (2 Leatherback and 2 Green nests, plus 1 Green half moon) and the 13th June (3 Leatherback and 1 Green nests). 4

4

10 /0 6/ 06

31 /0 5/ 06

21 /0 5/ 06

Loggerhead

11 /0 5/ 06

Hawkbill

01 /0 5/ 06

11 /0 4/ 06

01 /0 4/ 06

12 /0 3/ 06

02 /0 3/ 06

10 /0 6/ 06

31 /0 5/ 06

01 /0 4/ 06

21 /0 5/ 06

0

11 /0 5/ 06

0

01 /0 5/ 06

1

21 /0 4/ 06

1

11 /0 4/ 06

2

22 /0 3/ 06

2

12 /0 3/ 06

3

02 /0 3/ 06

3

Green

21 /0 4/ 06

B

22 /0 3/ 06

A

Leatherback

Figure 3-1. A) Seasonal nesting distribution of leatherback turtles. B) Seasonal nesting distribution of green, hawksbill and loggerhead turtles on the North Beach between March 1st and June 15th 2006.

0

0

Loggerhead 1/2 moon

1

2

1

1

Hawskbill 1/2 moon

Loggerhead nest

1/ 8 2/ 8 2 3/ 8 2 4/ 8 2 5/ 8 2 6/ 8 2 7/ 8

1

Green 1/2 moon

Hawskbill nest

2

1

2/ 8 3/ 8 4/ 8 5/ 8 6/ 8 7/ 8

2

3

2

2 1/ 8 2 2/ 8 2 3/ 8 2 4/ 8 2 5/ 8 2 6/ 8 2 7/ 8

3

1/ 8 2/ 8 1 3/ 8 1 4/ 8 1 5/ 8 1 6/ 8 1 7/ 8

3

1

4

2/ 8 3/ 8 4/ 8 5/ 8 6/ 8 7/ 8

4

Green nest

2

5

2

B

5

1/ 8 2/ 8 1 3/ 8 1 4/ 8 1 5/ 8 1 6/ 8 1 7/ 8

Leatherback 1/2 moon

1

Leatherback nest

3

6

A

1

6

Figure 3-2. A) Spatial nesting distribution of leatherback turtles. B) Spatial nesting distribution of st th green, hawksbill and loggerhead turtles on the North Beach between March 1 and June 15 2006.

The sectors of the beach with a higher density of nests were around mile 3/8 (7 nests and 3 half moons), mile 5/8 (6 nests and 0 half moons), mile 7/8 (5 nests, 1 half moon), mile 1 5/8 (5 nests, 1 half moon) and mile 2 7/8 (6 nests, 0 half moons). The sectors with a lower activity were between the miles 0 and 2/8 (0 nests ; 0 half moons), around mile 1 23

7/8 (1 nest, 1 half moon), mile 2 (1 nest, 1 half moon), mile 2 3/8 (0 nests, 1 half moon) and mile 2 6/8 (1 nest, 0 half moons). See figure 3-2 A & B for the spatial distribution (from Mile 0 to mile 3 1/8) of turtles nested on the North Beach. See Appendix B for a more detailed figure. 3.4.2.

Monitoring of nests

Out of the 71 nests on the North Beach until 15th June, 54% seemed to be left in their natural state without any signs of poaching, erosion or predation (Leatherback: n=29, Green: n=7, Hawksbill: n=1 and Loggerhead: n=1). Based on various evidence such as human foot prints, stick marks, egg shells and/or an exposed egg chamber, 35% of the total nests were poached (Leatherback: n=16, Green: n=4, Hawksbill: n=4 and Loggerhead: n=1). 4% of the nests were affected by the erosion (Leatherback: n= 3). Finally, the remaining 7% were from those nests where it was not possible to determine whether they were poached, eroded or left in their natural state. See the figure 3-3.

Natural Erosion Unknown Poached

35%

54%

7% 4%

Figure 3-3. Destiny of the nests (all species) on the North Beach between March 1st and June 15th 2006.

24

3.4.3.

Monitoring of female turtles

During the night surveys, 51 female sea turtles were observed during 8 of the 9 possible nesting activity processes. 18% were emerging from the sea (n=9), 10% were selecting the nest site (n=5), 8% were digging the body pit (n=4), 24% were digging the egg chamber (n=12), 12% were in the oviposition process (n=6), 16% were disguising the nest (n=8) and finally, 4% were returning to the sea (n=2). Furthermore, out of the 8% (n=4) of turtles which were observed attempting to nest, one Green was digging the egg chamber at the water edge and three times leatherback turtles came up on the beach but did not lay any eggs (observed selecting the nest site and twice the egg chamber was dug as well). Other females found on the North Beach were a dead Hawksbill turtle which appeared the morning of the 2nd April without any signs of poaching, and a lifted Hawksbill on the 10th June. The earliest turtle coming to nest at night was a Hawksbill found digging the egg chamber at 20:47. Yet, the latest turtle nesting could not be determined, since the beach was left at 02:00, between March 10 to June 4, and at 04:00, between June 5 and June 15. However, during the morning census, new turtle tracks (nests and half moons) were still being recorded. The hours that presented a higher nesting activity were between 23:00 and 01:30, where 67% (n=31) of the turtles were observed during the laying process. See figure 3-4. 16 Nesting turtles 14 12 10 8 6 4 2 0 20:00

20:30

21:30

22:30

23:30

00:30

01:30

02:30

03:30

04:00

Figure 3-4. Temporal activity distribution of the 4 studied species (error bars 5%) on the North Beach st th between March 1 and June 15 2006.

25

The orientation of the 27 females seen during the oviposition process was 4% heading North (n=1), 4% Northeast (n=1), 7% East (n=2), 11% Southeast (n=3), 15% South (n=4), 37% West (n=10) and finally 22% Northwest (n=6). See figure 3-5.

N 10 NW

8

NE

6 4 2 W

E

0

SW

SE

S

Figure 3-5. Nesting orientation of the 4 studied species (n = 27) on the North Beach between March 1st and June 15th 2006.

3.4.4.

Tagging

Of the total females seen during the night patrols, 15 (38%) were already tagged, 20 (51%) were newly tagged in 2 flippers (20% of them showing 1 or 2 evidences of old tag’s – OTH or OTN) and 4 (10%) were tagged in one of the flippers (100% of them with a minimum of 1 OTH). None of the newly applied tags were lost. The tags applied by Caño Palma Sea Turtle Monitoring Programme are shown in table 3.2 Monel tags VA8205-VA8208 VA8210-VA8214 VA8217-VA8218 VA8222-VA8224 VA8226 VA8228 VA8231-VA8232 VA8249

Iconel tags CP0001-CP0006 CP0008 CP0010-CP0019 CP0022-CP0025 CP0035 CP0041

Table 3-2. Tags applied by Caño Palma Sea Turtle Monitoring Programme from 1st March to 15th June 2006.

26

The 15 turtles that arrived to nest at the North Beach and were already tagged, came from other turtle monitoring programmes. 58% came from Tortuguero (tagged by the CCC), 12% from Playa Chiriqui, 24% from Pacuare, and 6% came from Playa Soropta in Panama, all of which are situated along the Caribbean Coast south of Tortuguero. The re-nesting interval from 4 leatherback turtles observed on the North Beach during the studied period was an average of 27.2 days. 3.4.5.

Biometric data

The mean carapace length, carapace width and clutch size (fertile and infertile eggs) of the leatherback turtles coming to nest in the North Beach during the studied period is shown in the Table 3-3. The mean carapace length of newly tagged individuals with no evidence of previous tags (OTH or OTN) was slightly higher (155.8 cm) that the mean carapace length of newly tagged females with old tag holes or notches (152.5 cm), and that of previously tagged females (148.5 cm). The mean carapace width of newly tagged females with no evidence of previous tags was also slightly higher (118.8 cm), than the other two categories (109.1 and 110.0 cm, respectively). The mean of fertile eggs was slightly higher for newly tagged females (88 eggs) with no signs of previous tagging than for the rest of females (67 and 75 eggs, respectively). On the other hand, the mean of the infertile eggs was very similar between the newly tagged without any evidence of old tags (25 eggs) and the previous tagged females (23 eggs), which were smaller than the mean of the newly tagged with evidences of old tags notches and holes (32 eggs). See table 31-3.

Sample Newly tagged no OTH/OTN Newly tagged with OTH/OTN Previously tagged

CCLmin (cm) N X ± ΣΤ.Δ. 6 3 17

155.8 ± 5.2 152.5 ± 0.4 148.5 ± 6.5

CCWmax (cm) N X ± ΣΤ.Δ. 6 3 16

111.8 ± 5.0 109.1 ± 1.2 110.0 ± 5.9

Fertile eggs

Infertile eggs

n

x ± ΣΤ.Δ.

n

X ± ΣΤ.Δ.

5 1 10

88 ± 5 67 ± Ν/Α 75 ± 16

5 1 10

25 ± 11 32 ± Ν/Α 23 ± 8.3

Table 3-3. Leatherback mean carapace length, carapace width and clutch size on the North Beach between March 1st and June 15th 2006.

The mean carapace length, carapace width and clutch size of green turtles is shown in table 3-4. As seen for Leatherbacks, the mean carapace length of newly tagged green with no evidence of previous tags was slightly higher (104.0 cm) that the mean carapace length of previous tagged females (90.8 cm). The mean carapace width of these newly 27

tagged green females with no evidence of previous tags was also slightly higher (93.9 cm), than the other category (78 cm). The number of fertile eggs was higher for the previous tagged turtles (132 eggs) than for the newly tagged (119 cm).

Sample Newly tagged Green no OTH/OTN Previous tagged Green

CCLmin (cm)

Clutch size

CCWmax (cm)

n

x ± ΣΤ.Δ.

n

X ± ΣΤ.Δ.

n

x ± ΣΤ.Δ.

7 1

104.0 ± 4.4 90.8 ± Ν/Α

7 1

93.9 ± 6.0 78.0 ± Ν/Α

4 1

119 ± 17.3 132 ± Ν/Α

Table 3-4. Green mean carapace length, carapace width and clutch size on the North Beach between March 1st and June 15th 2006.during.

The mean carapace length of newly tagged Hawksbill with no evidence of previous signs was a little smaller (89.3 cm) than the mean of previous tagged turtles (93.6 cm). Like for the carapace length, the mean carapace width of newly tagged hawksbills with no evidences was also smaller (75.5 cm) than for the previous tagged females (85.1 cm). However, the clutch size was slightly higher in the newly tagged turtles (151 eggs) than for the previously tagged (149 eggs). See table 3-5.

Sample Newly tagged Hawksbill no OTH/OTN Previous tagged Hawksbill

CCLmin (cm)

Clutch size

CCWmax (cm)

N

x ± ΣΤ.Δ.

n

X ± ΣΤ.Δ.

n

x ± ΣΤ.Δ.

2 1

89.3 ± 3.3 93.6 ± Ν/Α

2 1

75.5 ± 4.6 85.1 ± Ν/Α

2 1

151 ± 29.7 149 ± Ν/Α

Table 3-5. Hawksbill mean carapace length, carapace width and clutch size on the North Beach between March 1st and June 15th 2006.

As shown in table 3-6, the mean carapace length of newly tagged loggerhead with no evidence of previous signs was smaller (97.2 cm) than the mean of newly tagged loggerhead with signs of previous tags (100.4 cm). The mean carapace width of newly tagged females with no evidences was higher (91.7 cm) than for the other category (89.3 cm). No previously tagged loggerhead was seen during the studied period. Unfortunately it was possible to count only one Loggerhead clutch, and the number the eggs counted were 136. See table 3-6.

28

CCLmin (cm)

Sample Newly tagged Loggerhead no OTH/OTN Newly tagged Loggerhead with OTH/OTN

Clutch size

CCWmax (cm)

N

x ± ΣΤ.Δ.

n

X ± ΣΤ.Δ.

n

x ± ΣΤ.Δ.

1 1

97.2 ± Ν/Α 100.4 ± Ν/Α

1 1

91.7 ± Ν/Α 89.3 ± Ν/Α

1 0

136 ± Ν/Α N/A

Table 3-6. Loggerhead mean carapace length, carapace width and clutch size on the North Beach between March 1st and June 15th 2006.

The mean carapace length, carapace width and clutch size of the Leatherback found on more than one occasion, is shown in the Table 3-7. Three times the same turtle was found the CCWmax measurements had a higher level of precision than the CCLmin measurements. On the contrary, the measurements from the three turtles that were found on two occasions, the CCWmin had a lower precision than the CCLmin. See table 3-7.

Encounters 3 2

N 1 3

CCLmin (cm) X ± ΣΤ.Δ. Range 145.0 ± 1.2 150.6 ± 4.3

0.0 - 3.0 0.0-1.1

n 1 3

CCWmax (cm) x ± ΣΤ.Δ. Range 107.8 ± 0.3 109.9 ± 3.5

0.0 - 0.6 0.0-5.7

Fertile eggs

Infertile eggs

N

x ± ΣΤ.Δ.

n

x ± ΣΤ.Δ.

3 3

0±0 76 ± 10

3 3

0±0 30 ± 11

Table 3-7. Mean and range carapace length and width and clutch size of leatherback turtles found more than once on the North Beach between March 1st and June 15th 2006.

3.4.6.

Turtle disease or injuries

A total of 46 sea turtles were examinated after the oviposition process to monitor the external aspect of the turtle (bites, deformations or missing parts of the body, parasites, epibionts, etc.) and the possibility of disease like the fibropapilloma tumors. No individuals were recorded to be affected by fibropapilloma and only one turtle was found washed up by the sea, without any external mark or injuries. 70% (n=32) of the turtles examined had a minimum of one bite on their body. See figure 3-8.

29

Death, 1% Mutilations, 1% Carapace, 7%

Front right flipper, 21%

Epibiontes, 15%

Rear right flipper, 20%

Front left flipper, 13%

Rear left flipper, 20%

Figure 3-6. Distribution of the injuries presents on the turtles checked on the North Beach between st th March 1 and June 15 2006.

3.4.7.

Nest survivorship and hatchling success

From the seemingly 15 natural nests out of 71 total nests on the North Beach, only 5 hatched. For the other 10 nests, any evidence of emergence success was recorded. The 5 nests that hatched took an average of 63.4 days between the incubation period and the emergence of the hatchlings on the surface of the beach. The first nest marked by triangulation was on the 10th May, since then 14 more nests have been marked using the triangulation method. None of these nests will be excavated until 12th July. For this reason the hatchling success is not analyzed in this report. 3.4.8.

Human impact data

During the night surveys the presence of 2 strong torches (from the guards of Turtle Beach Lodge and Cabinas Vista al Mar) were recorded on almost all nights. White lights were observed 50% of the time throughout the night patrol, as well as fishermen, bonfires, tourists and local people walking the beach at night. In various places along the beach, a few permanent lights have been observed, including a very bright external light on the top part of the beach in front of Turtle Beach Lodge. This was changed for a red light at the beginning of May. Moreover, a fishing line just before mile 1, of approximately 50 meters length, was recorded on all nights. 30

3.5. 3.5.1.

Discussion Daily track census and nest surveys

Although Leatherback nesting was observed from 2nd March to 15th June, the nesting season on the Caribbean coast ranges from March to mid-July (Troëng et al., 2004 ), and thus this report does not reflect the total Leatherback nesting season. At the time of writing Leatherbacks are still coming up to nest on the North Beach as well as other species (Greens, Hawksbills, and Loggerheads). The total number of nests recorded on the North Beach during this study was 71. More than half of the turtles were seen during the night patrols, thanks to the large number of hours and miles walked on the beach. The majority of these nests were from leatherback turtles, however a considerable number of nests from other species were also recorded between March and mid-June. Especially those of green and hawksbill turtles, which started to arrive, on 23rd and 26th April, respectively, more than one month previous to their respective nesting season beginning in June. The seasonal distribution of leatherback turtles was higher between 13th and 30th of April and between 17th May and 14th June. If we add the four species together, the higher densities were between 13 April and 5 May, 17 May and between 24 May and 13 June. See Appendix A. The higher density of nests per mile was found at the first stretch of the beach, between mile 0 and 1, with a 42% of total nests. The sectors between mile 1 and 2 and between 2 and 3, had both 30% of the nest. In particular, the actual zones with the higher density were at mile 3/8, mile 5/8 and at mile 2 7/8. See Appendix B. 3.5.2.

Monitoring of nests

Illegal take of turtle nests was recorded throughout the entire study period. A minimum of 31% of the Leatherback nests were poached, as well as 33% of Green, 50% of Loggerhead and finally 80% of the Hawksbill nests. The very low levels of nesting Hawksbills observed in the Tortuguero area are disconcerting. To ensure increased Hawksbill nesting in the future, any action aimed at protecting nesting females, nests or 31

females in the internesting habitat should be encouraged (Da Haro & Troëng, 2005). Hawksbill nesting at Tortuguero are now at such low levels that every female and nest are important (Troëng et al. 2005). Although we estimated the minimum poaching rate for each species, this does not reflect the actual poaching that occurs on the beach. One of the causes of this under-estimation is due to the act of erasing tracks and nests once recorded on the beach. This act has three big consequences: 1. The night patrol has to stay with the turtle throughout the nesting process (sometimes more than two an a half hours) in order to be able to erase the tracks afterwards. In this way, other turtles that are nesting at the same time in other parts of the beach are lost, i.e. not recorded (a nest was found during the night but not the turtle in 14 % of the total time spent on the beach. See 3.3.2). 2. There is a risk of damaging the nest when erasing tracks and attempting to camouflage the bodypit, such as excessive compact sand on top of the nest. 3. Erasing the tracks could be encouraging illegal harvest of the eggs and poachers could also erase new tracks without leaving any evidence of the harvested nest and thus causing inaccuracies in the data collection. For those reasons, the erasing of tracks was stopped in May. The final report of the Leatherback Nesting Season 2006 will be able to give an indication of whether the illegal harvesting of the nest is statistically different with or without erasing the tracks. In order to protect the hawksbill nests as much as possible, an exception to the above was agreed to apply in that the tracks will be erased after all Hawksbill encounters, with the purpose to minimize the possibility for the poachers to find the nest. In comparison to the previous years, the poaching rate on the North Beach is decreasing (COTERC Report 2006, unpublished), and as shown in others Sea Turtle Monitoring Programmes, the constant presence of the researchers on the beach may be one of the major reasons for the reduction of illegal harvests.

32

3.5.3.

Monitoring of female turtles

91% of the times the turtles came out to nest between 21:30 and 01:30 and 52% of those were between 23:30 and 00:30. For this reason, the division of the night patrols in two shifts (20:30 to 00:30 and 00:00 to 04:00), covering all the peaks of the higher density hours, will be continue until a change of this density. The study of the orientation of the turtles when nesting will continue. At the moment it seems that the favourite orientation of the turtles while there are nesting is west, followed by northwest and south. 3.5.4.

Tagging

During the 507.5 hours of night patrol and a total of 39 worked turtles, 4 did not have any tags and presented one or two OTH or OTN, and other 4 other had only one tag and also presented one or two OTH or OTN. This information will be very useful in terms of estimating tag loss and annual survival probabilities (Da Haro & Troëng, 2005). On the other hand, it is known that other projects along the Caribbean Cost of Costa Rica, with a bigger population of leatherback turtles (with the exception of the CCC) are also tagging using PIT tags (Passive Integrated Transponder) placed under the skin. These PIT tags are read using a scanner device. Since leatherback turtles can travel relatively long distances during the same nesting season (L. Chaparro, pers comm.), it is possible that a number of turtles, in particular those presenting old tag notches or holes, possess a PIT in their bodies which we can not detect on the North Beach because of the absence of the required equipment. Future investigation, in particular for the Leatherback turtles, could prove the need of this kind of expensive equipment. 3.5.5.

Biometric data

Mean carapace measurements of previously tagged leatherback and green turtles were smaller than those of newly tagged with evidences of old tag or notches and smaller than the newly tagged without evidences. On the contrary, the mean carapace measurements of previously tagged hawksbill were greater than those of newly tagged without evidences of old tag or notches. With the loggerhead turtles, the mean carapace length of the newly tagged with evidences was higher than the one without evidences 33

but the mean carapace width was the reverse. In theory (L. Chaparro, pers. comm.), the newly tagged turtles (assumed younger) are in general smaller than the previously tagged turtles (assumed older), but so far this theory could only be applied to the hawksbill measurements. One of the reasons for these results could be that this is the first year that a tagging programme is taking place on this beach. Consequently, we are not able to identify the re-migrating turtles (turtles that came to nest in previous years) from the neophytes ones (turtles that reach the sexual maturity for the first time). In this way, the inter-nesting females that were not previously tagged by other turtle monitoring programmes do not present any evidence of old tag holes or notches. Thus they are mixed with the neophytes that come to nest for the first time, and the mean carapace measurements do not necessarily reflect the reality. Despite this fact,

thanks to encountering re-nesting turtles, the precision could be

calculated and the higher range obtained was between 0.0 to 3.0 centimeters for the length and 0.0 to 5.7cm for the width, showing that the precision obtained with the length measurement was higher than the width. Consequently, training of correct and precise measuring techniques of the length and width of the carapace of the four different species is of extreme importance and urgency. During next phase such training will be provided in order to make sure that measurements are recorded as precise and accurate as possible. 3.5.6.

Turtle disease or injuries

Out of the 46 individuals examined, not one was recorded to be affected by fibropapilloma tumors. However, the majority of these females (n=32), presented a minimum of 2 bites somewhere on the body, the majority of bites located on the right front flipper and on both rear flippers. 3.5.7.

Nest suvivorship and hatchling success

Until the end of this study, only 33% of the nests that should already have hatched did in fact hatch. Because the triangulation of nests did not start until the 10th of May, the reasons for this low rate of emergence success can not be estimated. However, this low emergence success could be due to an actual higher rate of poaching than the recorded. 34

In addition, a large number of nests were next to the high tide potentially causing inundation or erosion of various nests, and the low success could also be due to depredation inside the nest, infertile eggs or females and a variety of other factors not mentioned here. Excavations of the nests will start next phase, on 12th July. These excavations should give provide further information about the final destiny of the eggs on the North Beach. The results will be presented in the final Leatherback Nesting Season 2006 Report. 3.5.8.

Human Impact Data

Turtle Beach Lodge have shown a noticeable conservation effort as, in the middle of the Leatherback Season, they changed the very bright external light placed on the top of the beach for a less powerful red light. COTERC and GVI have been able to establish a good relationship with the growing village of San Franciso and the increasing human settlers on the parallel trail of the beach through various presentations, invitations to join us on the beach, environmental education and English lessons, and it is hoped that this will aid in reducing the poaching rate on the beach.

35

4.

EBCP RESIDENT BIRD PROJECT 2

4.1.

Introduction

Over the past 40 years northeast Costa Rica has been under much scientific focus due to its extensive primary lowland and coastal rainforests and also the largest nesting colony for the endangered Green Turtle (Chelonia mydas). Because of the geographical location, a large amount of investigation into the migratory avifauna of the New World has also been conducted in this part of Costa Rica. Though quite a bit is known about Costa Rican birds, and in particular the migratory species that either winter in Costa Rica or pass through, an astonishing amount remains to be learned about the residential species. Because of this and the growing concerns about the status of birds of the rainforests in Mesoamerica, a long-term monitoring station has been established in the area of Tortuguero. Estación Biológica Caño Palma (EBCP) is based 7km north of Tortuguero National Park on the Caño Palma canal that runs parallel to the coast. Avifauna monitoring programs in the past have combined the use of area searches, constant-effort mist netting, and migration counts. This protocol is intended to gather data that will shed light on the natural history of resident birds as well as the migratory species in 4 different habitats using area searches, point counts and various other techniques. The GVI protocol is a slight modification of the protocol created by Steven Furino of Waterloo University, Canada to take into account the use of a number of different recorders. In all other aspects the research will follow the protocol created by Steven Furino.

2

The information in the introduction and methodology of this section of the report has been

directly taken from the protocol developed by Steven Furino. Some adaptations have been made where field experience has identified more suitable ways of undertaking the research.

36

4.2.

Aim

This research program is intended to accumulate data that will allow researchers to answer, at least in part, the following questions. •

How frequently do pelagic species visit the Caribbean Coast? Is there any pattern to their visits?

•

When, exactly, do resident birds breed in coastal areas and swamp forests?

•

What can be learned about the breeding and nesting behaviour of resident birds?

•

Are breeding activities and climate correlated?

4.3.

Method

This project has adopted standard survey techniques so that suitable comparisons can be made against data sets gathered by other researchers. For each Resident Bird Project (RBP) survey the following general data is recorded: •

Name of study site

•

Ground moisture

•

Name of surveyors

•

Rainfall

•

Date of survey

•

Start time (using a 24 hour clock)

•

Cloud cover

•

End time (using a 24 hour clock)

For further information on the categories used to assess climatic conditions see appendix C. 4.3.1.

Point Counts

A point count survey records all study species 3 seen or heard in a ten minute period at a predetermined location. Point counts are conducted in conjunction with area searches. See appendix C for exact locations for each point count station. Point counts allow researchers to use statistical techniques to assess the density of bird populations.

3

Study Species are subdivided into habitat types – see appendix A

37

Surveyors record all study species positively identified in an exact 10 minute span. The point stations are not left during this period unless it aids in the identification of a bird. For each positive record made the following data should be collected: •

Point count station at which species was observed

•

Time at which species was first recorded

•

Number seen or heard (S: seen only, H: heard only, SH: seen and heard)

•

Distance from observers (0-10m, 11-25m, 26-50m, 50m +)

•

Height within habitat (G: ground, L: Low, M: Medium, H: High, A: Arial)

•

When possible, the number of males, the number of females and the number of subadults/adults

•

Any notes on breeding plumage or behavior

A more structured method of recording breeding behavior has been introduced this phase. Examples of behaviors which are recorded include: courtship displays; nest building; copulation; and feeding young (see appendix B for further details). For this protocol, only behaviors that are strongly correlated with probable or confirmed breeding are recorded. 4.3.2.

Area Searches

An area search records all species seen or heard while searching a predetermined area. See appendix C for exact locations of each area. Within each area, sectors have been selected to aid with data collection and analysis. These sectors have been selected on various habitat variables and enable a similar unit effort to be used on all surveys. For each area search surveyors record only the selected study species for that habitat. As with the point counts only positively identified species are recorded. Any rare birds seen during surveys were recorded as incidentals. For each positive record made the following data should be collected:

38

•

Point count station at which species was observed

•

Time at which species was first recorded

•

Number seen or heard (S: seen only, H: heard only, SH: seen and heard)

•

Distance from observers (0-10m, 11-25m, 26-50m, 50m +)

•

Height within habitat (G: ground, L: Low, M: Medium, H: High, A: Arial)

•

When possible, the number of males, the number of females and the number of subadults/adults

•

Any notes on breeding plumage or behaviour

4.3.3.

Incidental Observations

An incidental observation is an observation made while one is not engaged specifically in area searches or point counts. Incidental observations cover all of the other times of day when birds might be observed. This includes relaxing in the rancho, eating dinner, and birding whilst not on survey. Only species that have been classed as rare, vagrant, hypothetical or unknown in the Checklist to the Birds of Tortuguero were recorded. In order to maintain a high standard of competency in the field both staff and Expedition Members were given bird identification training and tests on a regular basis. The training involved both in the field bird identification and laboratory training using Powerpoint presentations. The presentation consisted of a mix of photographs, drawing and audio bird calls to provide the EMs with a wide selection of examples of the key spices.

39

4.4. 4.4.1.

Results Survey Data

12

10

8

6

4

2

0 AM

PM CA

AM

PM

AM

CT

PM NB

AM

PM CP

Figure 4-1 Distrubution of survey periods and study sites during Phase 4.

During Phase 4 a total of 56 RBP surveys were undertaken. Of these 17 were undertaken on the Cleared Areas study site (10 dawn and 7 dusk), 13 on Cerro Tortuguero (5 dawn and 8 dusk), 12 on the North Beach study site (7 dawn and 5 dusk) and 14 on Caño Palma (9 dawn and 5 dusk).

40

Pa ss e hi rini t ' e W -c s T hi an r te ow a Pa -rin ned ger g le e P d -b a ille Fly rro t c d W atc o he Sq od r Bo ui pe c rr a Th t-bi el C ker lle ic u d ck kF bi lle lyc oo at d c S Ea ee her st d-F er n inch G K ra y- Pal ing b ca m pp T ird ed ana R Fly ger ed c -lo atc h O Tro red er liv e- pica par ba ro l c k K in t ed gb Eu ird Bl M pho ac e n S a kch oci ly P ia ee al a ke Fly rro t d c W atc Bl ue ood her Bl ac p k- gra eck m y er T an di ana bl g Le e T er ss ou e c C r G an ol re l Ke are en le d el t A -b ille rac C l ar ay M d i on T te colo ouc zu m red an a Bl ue Or Rob o -b i la pen n ck do G Gra la r Va eat ssq u ria Ki sk it bl ad e Se e ed e ea te r W

90

80

70

60

50

40

30

20

10

0

Figure 4-2 Key species recorded during surveys of the Cleared Areas study site.

A total of 26 species were recorded within the Cleared Areas study site. The top four

species were Montezuma Oropendola (Gymnostinops

41 Montezuma), Blue-black

Grassquit (Volatinia jacarina), Great Kiskadee (Pitangus sulphuratus) and Variable

Seedeater (Sporophila corvine) accounting for 49% of all records within the study site.

16

14

12

10

8

6

4

2

Bl

G re en

re at G

Am

az on

Ki n

gf is he r

ue H er Ba on ck ed H er on Sn ow y Eg re t Su ng re G re be at Ti na m Li ou ttl R e uf T e in sc Ye am en llo tT ou w -c ig ro er w H Am ne er d er on N ic ig an ht -H Py er gm on y Ki ng fis Ba he re C r -th at tle ro at E ed gr et Ti ge r-h G er re on at C ur as G re so en w Ki n R g fis in ge he d r Ki ng fis he r G re A en nh -B in ga ac ke d H er on G re en Ib is

0

Figure 4-3 Key species recorded during surveys of the Caño Palma study site.

A total of 18 species were recorded within the Caño Palma study site. The top four species were Green Ibis (Mesembrinibis cayennensis), Green-Backed Heron (Butorides virescens), Anhinga (Anhinga anhinga) and Ringed Kingfisher (Ceryle torquatus) accounting for 54% of all records within the study site.

42

20 18 16 14 12 10 8 6 4 2

Bl a

ke d

ck -c he e

Bl a

Ba r

re dW oo

dc re ep e

r W oo dp ck ec -T ke hr r oa te Pa d le Tr -b og ille on d W Pl oo ai ndp br ec ow ke n r W oo dc re Br ep ig ht er -ru m pe d At til C a ol la re d Ar Sh ac or ar t-b i ille C he d st Pi nu ge t-b on ac k W ed es An te tb rn ird Sl at yAn ts hr ik Le e ss er G re Sl en at le yt ta ile Bl d ac Tr kog m on an di bl e To uc Ke an el -b ille d To uc an

0

Figure 4-4 Key species recorded during surveys of the Cerro Tortuguero study site.

A total of 14 species were recorded within the Cerro Tortuguero study site. The top four species were Keel-billed Toucan (Ramphastos sulfuratus), Black-mandible Toucan (Ramphastos swainsonii), Slaty-tailed Trogon (Trogon Massena) and Lesser Greenlet (Hylophilus decurtatus) accounting for 64% of all records within the study site.

43

40

35

30

25

20

15

10

5

w n

Pe lic an

ip er Br o

Sa nd p ot te d

Sp

M ag ni fi

ce nt

d

Fr ig

Pl

at eb i

rd

ov er

el el lie ck -b Bl a

Pl ed

W hi m br

ov er

n Te r m ip al m at

Se

R oy al

lin g nd er Sa

Pl ov er ol la re d

C

W ils

C pi c N

eo tro

on 's

m or an or

n ow Br

Pl ov er

t

Bo ob y

0

Figure 4-5 Key species recorded during surveys of the North Beach study site.

A total of 12 species were recorded within the North Beach study site. The top four species were Brown Pelican (Pelecanus occidentalis), Spotted Sandpiper (Actitis macularia), Magnificent Frigatebird (Fregata magnificens) and Black-bellied Plover (Pluvialis squatarola) accounting for 71% of all records within the study site. 4.4.2.

Incidental Observations

14/04/2006

AM

18/04/2006 10/05/2006

AM AM

Tortuguero National Park Beach North Beach Cano Palma

2 x Black-necked Stilt Mangrove Cuckoo Roseatte Spoonbill

Table 4-1 Incidental recordings of rare species observed during phase 4.

Three rare species were observed outside of surveys. All of the species seen were observed by more than one person and a detailed description of the species was taken to confirm identification. In the case of all these species miss-identification would be unlikely. 44

4.5.

Discussion

The EBCP Resident Bird Project monitoring surveys began in July of 2005 and will continue for several years. As the study is only in its fourth phase, this early set of data can not be taken as indicative of trends for local bird species. The data obtained in this phase was collected using different methodology to that used during the previous phases. The methodology had a limited list of target species therefore no information on which of the study sites contains the highest or lowest species diversity could be ascertained. This information has however been established in the previous phases and was therefore deemed not necessary to confirm in this phase. The technique of using both area searches and point counts to conduct monitoring surveys works as an effective indicator to determine the local bird presence. The two survey techniques were combined in this phase to coincide with methodology established by Steven Furino and allow a greater number of surveys to be undertaken. During Phase 4 a total of 56 RBP surveys were undertaken. The original aim was to achieve an equal number of surveys per study site and an equal number of dawn and dusk surveys within each study site. The complexities of the expedition meant that this was not always possible however the numbers were kept relatively constant (see figure 4.1). Comparison between study sites is no longer examined as variation in the newly adopted key species lists as they do not lend themselves to this form of comparison. Data collected on individual study sites will be used over time to assess how certain populations are changing, if at all, and how they use the specific habitat over the course of a year. To aid with the WINGS database created by Steven Furino, the programme will finally be installed on the Caño Palma computer and from Phase 5 it will be used directly by the expedition in order to add all future data. The findings from this phase do not highlight any unexpected or unusual patterns in the local bird populations. There has been a clear decline in certain species such as the shore birds and some waders during this phase compared to last phase, specific examples include Semipalmated Plover (Charadrius semipalmatus) and Little Blue 45

Heron (Egretta caerulea). The decline in the presence of the species can be attributed to normal migrating behaviour as these species breed in North America and only some non breeding individuals will remain in Costa Rica. Breeding evidence of a variety of species was recorded during the Phase 4 surveys. Species confirmed as breeding include, Great Kiskadee (Pitangus sulphuratus), Montezuma Oropendola (Psarocolius montezuma), Rufous-ailed Hummingbird (Amazilia tzacatl), Yellow-crowned Night-Heron (Nyctanassa violacea), Long-billed Hermit (Phaethornis longirostris), Bare-throated Tiger-Heron (Tigrisoma mexicanum), Greenbacked

Heron

(Butorides

virescens),

Black-cheeked

woodpecker

(Melanerpes

pucherani) and Clay-colored Robin (Turdus grayi). Some of these records were obtained off survey or during preliminary nest searches. In addition to these confirmed records there was also a highly probable record of nesting Green Ibis (Mesembrinibis cayennensis). The lack of data on the breeding and nesting behaviour on this species makes this finding very important and further work next phase will help to gain data on this species. The level of bird watching in personal time and the amount of previous birding experience this phase was noted to be much lower than that of last phase. It is reasonable to assume that these factors resulted in a much lower number of incidentals being recorded. In respect to rare species recorded of survey only three species were recorded which were Mangrove Cuckoo (Coccyzus minorm), Black-necked Stilt (Himantopus mexicanus) and Roseate Spoonbill (Platalea ajaja). The EBCP Resident Bird Project surveys undertaken during Phase 4 have assisted in increasing the overall data set. They have also helped in identifying areas where continued improvement to the methodology is required in order to gain the most useful and accurate data possible.

46

5.

NATIONAL PARK TOURIST IMPACT ASSESSMENT

5.1.

Introduction

With 622,000 ha or 12.2% of the country set aside in preserves, Costa Rica’s National Parks stand as a model for the preservation of biodiversity in the tropics (Boza, 1993). These magnificent wild lands provide shelter for some 205 species of mammals, 845 species of birds, 160 species of amphibians, 218 species of reptiles and 1,013 species of freshwater and marine fishes that have been discovered in the country (Boza, 1993). 10,000 of species of vascular plants have been identified to date which account for almost 4% of the total number of plant species in the world (Boza, 1993). This diversity of wildlife is encapsulated within a variety of habitats found in Costa Rica. Tortuguero National Park, located on the upper Caribbean coastline of Costa Rica was established between 1970 and 1971 along with 3 others in this region. The Park is managed and protected by the Costa Rican Ministry of Environment and Energy (MINAE). Terrestrial sections of the National Park consist of primary rainforest and flooded swamplands which extend from the Caribbean coastline to the foothills of the central Costa Rican mountain range. Within the Park’s boundaries exists a sequence of terrestrial and aquatic trails clearly marked to allow tourists the opportunity to experience the impressive species richness of the areas 2,200 species of plant, 375 birds, 125 mammal species and 124 species of reptiles (Hocken et al., 1992; cited in Hill et al., 1997). Controversy has arisen in recent years over the extent to which humans uses of such reserves may have adverse effects of wildlife. These uses include tourism, recreation and industrial development. Therefore there is considerable conservation interest in quantifying the effects of such disturbance upon the diversity that exists here (Hocken et al., 1992; cited in Hill et al., 1997). The flow of tourists to the National Park is regulated by MINAE. Greater accessibility to this region has begun to create an additional constant influx of tourist groups into the Park using both the aquatic and terrestrial trails. Since 1998 annual totals of visitors to the Park have risen from 15,000 to 92,000 in 2005 (C. Calvo, pers. communication). Although tourism is encouraged by the local community, MINAE and the national economy, a certain balance between the Park’s human activity and the conservation of these fragile ecosystems should be respected. Thus there is a potential threat to the biodiversity of the Park due to excessive stress from this continuous activity. Initiation of 47

this study is in direct response to growing concerns of the negative impact tourism is having on the National Park. Assessing the severity of the effects of disturbance has important practical consequences; if it has serious impacts conservationist are justified in recommending that access to wildlife areas be limited (Burger, 1981; cited in Gill et al., 2001). However if the impacts of disturbance are trivial then such measures cannot be justified. Restricting human access to these areas can be expensive and time consuming but more importantly it goes against the increasing view that rural access should be increased. In many cases access to areas of conservation value can be the optimum way to protect them as it increases the value placed on them by society (Adams, 1997; cited in Gill et al., 2001). Disturbance is often implicated as having potentially damaging effects on wildlife (Hume, 1976; cited in Gill et al., 1996). The critical factor in the field of conservation is whether disturbance results in lower population sizes. Batten et al (1990) (cited in Hill et al., 1997) interviewed a large number of ornithologists in the UK and concluded that 49 out of 117 species listed on the Red Data Birds List in the UK were potentially affected or threatened by some form of disturbance. The sources of this human disturbance were identified to include water based recreation, walking in remote countryside and large scale developments (particularly on estuaries) and hunting. Conversely, this is not the case in all species, as for example it was found that human disturbance had no effect on the numbers of Black-tailed Godwits (Limosa limosa) supported on coastal sites at a range of spatial scales (Gill et al., 2001). The approach currently being adopted in this study addresses a broad community using species composition and population as an indication of habitat type and quality. This allows the status and trends in the condition of the ecological system over the region to be assessed by the identification of existing or developing problems prior to a crisis. Thus far the complex and diverse nature of ecological systems necessitates the use of appropriate validation of some restricted set of indicators of biological condition to allow efficient monitoring over a range of systems (Canterbury et al., 2000). Species are proposed as environmental indicators under the assumption that the responses of individual species are representative of the responses of other species within a habitat

48

or community (National Forest Management Act Code of Federal Regulation 1985; cited in Canterbury, 2000). The indicator species concept has been criticized however because individual species do not necessarily reflect trends in other co-occurring species (Morrison, 1986, Laudres et al., 1988; cited in Canterbury et al., 2000). Nevertheless, as in this case, bio-indicators can be useful indices of environmental conditions where initial in depth studies are too expensive, complicated or too difficult to undertake (Azevedo-Ramos et al., 2002) Birds are often seen as one of the simpler taxa to employ as a bio-indicator. As a group they tend to respond very well to various changes in habitat quality within a variety of niches whilst fulfilling a variety of important ecological functions (Rutschke 1987, Whitman et al., 1998). In addition to these factors avian species are generally easy to locate and it is also possible to train surveyors to recognize a limited avian species list within a short period. However, interpreting such a study can be difficult because variations in disturbance are often confounded by factors such as prey density, competition or predator density or the locations of territories nests or roost sites (Gill et al., 2001). In addition, birds or any other highly mobile organism may fail to be reliable indicators of the local resource conditions being monitored because populations could be affected by habitat conditions (Temple and Wiens, 1989; cited in Canterbury, 2000) or their presence or absence during these periods throughout the year. Even so, such information is necessary in order to demonstrate whether disturbed sites support fewer animals than the resources would potentially allow and to quantify the extent to which the use of such sites could be increased if disturbance was absent. The impact of tourist presence can also be measured through direct measurements of physical factors such as path width, level of erosion and litter. All of these factors enable a very simple assessment of tourist impact to be produced whilst enabling a useful and often immediate tool for management. Funded by the European Union, in 2005 MINAE developed a Management Plan for visitors to Tortuguero National Park. GVI were requested to initiate and implement the Tourist Impact Assessment in order to provide data for an objective and quantitative evaluation of the impact of tourism in this National Park. In order to gain as much data 49

on tourist impact a number of studies recommended in the Management Plan have been initiated examining both environmental and physical effects. 5.2.

Aims

The Tortuguero National Park Tourist Impact Assessment aims to provide MINAE with suitable data to aid with management decisions in relation to tourist use of the parks resource. This is achieved through a variety of survey methods that assess physical and ecological characteristics of the National Park. 5.3.

Methods

Three phases of data collection have been undertaken by GVI since October 2005. This baseline data has resulted in a good understanding of the ecological systems operating in and around the park. As this understanding continues to develop, methodology is adapted to yield the most beneficial results possible. The National Park Tourist Impact Study consists of five separate research areas, these are: •

Aquatic Survey

•

Terrestrial Survey day and night

•

Strawberry Poison Dart Frog Transect

•

Assessment of visitor use of aquatic trails within the National Park

•

Assessment of terrestrial trail condition

The data obtained from these five research areas is helping to establish a realistic view of what is happening within the park both on an ecological level and a tourist presence level. 5.3.1.

Aquatic Trails

This part of the study involves surveying two aquatic transects within the National Park; Caño Harold and Caño Chiquero. Transects are commenced between 05:40am and 06:50am on a weekly basis for both Caño Harold and Caño Chiquero. Caño Harold is also surveyed before dusk, commencing at between 13:50 and 15:00. Up to six 50

researchers undertake the survey recording all tourist impact key species seen and or heard, (see appendix A for species list). The data collected during the aquatic surveys falls in two categories; general survey data and species data. For each survey the following general data is recorded: •

Name of study site

•

Leaf drip

•

Name of surveyors

•

Rainfall

•

Date of survey

•

Start time (using a 24 hour clock)

•

Cloud cover

•

End time (using a 24 hour clock)

•

Ground moisture

For further information on the categories used to assess climatic conditions see appendix C. In addition to this, if climatic data changes during the survey it is also recorded. Each study site has been divided into sections to aid with data recording and analysis. Caño Harold is divided into five sections whilst Caño Chiquero is divided into four sections. The access sectors AC1 and AC2 are the first two sectors to be surveyed on either Caño. The beginning of AC1 is located at the start of Rio Tortugero and continues along the Caño until it reaches the westerly Caño which leads to both Caño Harold and Chiquero. At this point AC2 begins and continues in a westerly direction towards Caño Harold. Where Caño Harold enters AC2, CH1 begins. CH1 continues up Caño Harold leading into CH2 and CH3 along the way. The survey of Chiquero continues to pass Caño Harold along AC2. Where AC2 leads into Caño Chiquero, CC1 begins. The transect continues up this Caño along which CC2 is also located (see Appendix D for further reference). For each studies species recorded the following specific data is recorded: •

Species

•

Time at which species was first recorded

•

Location (sector)

•

Number seen or heard (S: seen only, H: heard only, SH: seen and heard)

•

Height within habitat (G: ground, L: Low, M: Medium, H: High, A: Arial)

51

•

When possible, the number of males, the number of females and the number of subadults/adults

•

Any notes on breeding plumage or behavior (see appendix B for more details)

All individuals are identified to species level where possible; where this cannot be achieved family name is recorded. Any unidentified individuals are not recorded. 5.3.2.

Terrestrial Trail

The Sendero Gavilán is a terrestrial loop trail, 1,920 meters long, located immediately south of the Park Headquarter, Cuatro Esquinas (Point 0 of the trail). Up to four researchers commence at Cuatro Esquinas, and walk counter-clockwise around the trail. Data is collected using the same methodology as with the aquatic survey (see section 2.3.1) The trail is broken into four sectors: •

G1 – Trail head to 550 meters

•

G2 – 550m to 1100m (at the path parallel to the beach)

•

G3 – 1100m to 1500m (the trail parallel to the beach)

•

G4 – 1500m (the water tower) to the trail head

This survey was undertaken during both day and night time hours. During night time hours a significantly lower proportion of the transect was covered due to the associated difficulties of night time surveying. 5.3.3.

Strawberry Poison Dart Frog transects

Presence/absence data is collected on Strawberry Poison Dart frogs (Dendrobates pumilio) along three transects. One is situated 100m west from the trail Sendero Gavilán and two are situated 500m and 1000m south from Sendero Gavilán. This frog species is believed to have declined possibly to the point of local extinction within this area of the National Park.

52

Surveyors follow the transect at a slow pace taking time to thoroughly examine the area within one meter (1m) from either side of the transect, taking particular interest under leaf litter, within bromilidaes and around any dead wood encountered. 5.3.4.

Assessment of visitor use of aquatic trails within the National Park

In order to verify the data collected by the ranger service at Cuatro Esquinas, GVI undertook surveys within the aquatic trails of the National Park to accurately quantify the volume of traffic passing through the canals within the park. Surveyors were located at the entrance of Caño Chiquero where they were able to determine which Caños visiting boats were traveling down. Surveys were undertaken on all seven days of the week between the hours of 06:00 and 18:00. At no point during this period was the survey point left unattended. 5.3.5.

Assessment of terrestrial trail condition

The presence and development of extensions and divergences along the Gavilán Trail system in Tortuguero National Park was assessed. Measurements began from the Park Headquarter at Cuatro Esquinas (Point 0 of the trail) going south along the trail in a counter-clockwise direction. Extensions were classified as those areas where the path is wider than the originally cut two meters. Trail extensions were recorded at the widest point and the length of the widened area noted. Extension specifics included the widest part of the area noted as the centre width with measurements taken one meter above and one meter below the centre width. The total length of the extension was measured as main trail length (see Appendix E for photo examples). Divergences were classified as those areas where a second, usually parallel, path has been artificially created. The divergences were determined as right or left when walking south along the trail. Divergence specifics included the entrance width of the divergent path off the main trail (entrance width), length of the divergent trail from the entrance to the point where it rejoined the main trail (divergence length), width of the divergent trail where it rejoined the main trail (exit width), length along the main trail that the divergent

53

trail spanned (main trail length) and the maximum distance the divergent trail diverges from the main trail (distance from the trail). 5.4. 5.4.1.

Results Aquatic Trails

A total of 33 aquatic surveys have been undertaken in the National Park study area during 2006, of these 24 were conducted on Caño Harold and 8 on Caño Chiquero. |During the summer surveys, 7 surveys were undertaken on Caño Harold and 2 on Caño

Total recorded during summer

Total recorded in 2006

0 2 0 17 0 1 2 1 1 3 5

1 0 7 7 1 1 0 1 0 1 6

0 0 0 4 1 0 1 1 0 1 0

0 0 0 0 1 0 1 0 0 0 0

13 5 43 94 85 0 0 8 19 8 81

2 5 13 67 5 5 5 10 3 6 18

15 10 56 161 90 5 5 18 22 14 99

5 3 11 12 4 21 7 84

0 0 35 9 6 0 7 60

17 3 81 0 6 43 4 178

3 2 79 0 13 3 6 121

4 3 47 0 9 3 8 114

1 2 27 0 0 1 1 37

0 0 4 0 0 0 6 10

2 0 2 11 1 0 2 24

0 0 0 1 1 0 0 2

0 0 7 0 2 0 0 13

0 3 5 0 5 6 1 29

0 0 5 0 0 7 1 20

0 0 0 0 0 0 2 3

0 0 0 0 0 0 1 1

30 13 284 21 38 71 39 604

2 3 19 12 9 13 7 92

32 16 303 33 47 84 46 696

Totals

Total recorded during winter

0 0 4 15 2 3 1 1 0 1 3

CC2 during summer

0 0 0 2 0 0 0 1 0 0 0

CC1 during summer

1 3 2 22 0 0 0 5 2 0 4

CH3 during summer

0 1 1 0 0 0 0 1 0 0 0

AC2 during summer

0 0 0 3 0 0 0 0 0 1 4

AC1 during summer

8 1 22 16 8 0 0 1 0 2 38

CC2 during winter

4 3 2 1 6 0 0 0 4 4 7

CC1 during winter

0 0 3 32 55 0 0 3 0 1 23

CH3 during winter

0 0 1 8 3 0 0 0 2 0 1

CH2 during winter

CH2 during summer

Chloroceryle amazona Chloroceryle aenea Anhinga anhinga Tigrisoma mexicanum Rhinoclemmys funerea Cochlearius cochlearius Aramides cajanea Crax rubra Ardea alba Chloroceryle inda Butorides virescens Mesembrinibis cayennensis Chloroceryle americana Egretta caerulea Jacana spinosa Ceryle torquatus Egretta thula Heliornis fulica

CH1 during winter

Species

AC2 during winter

1 0 14 34 13 0 0 3 13 0 8

AC1 during winter

CH1 during summer

Chiquero. The winter surveys involved 18 surveys on Caño Harold and 6 on Chiquero.

Table 5-1 Number of the most common key species observed during each study phase based on Caño location.

The above data (Table 5-1) was extracted from a dataset examining the frequency of observations for 33 key species. A total of 1444 observation were made of the species during the two study periods. 18 of the 33 key species observed were identified as being common during either the winter, summer or during both phases. These species account 54

for 696 (48% of all records) records, the majority of these observation were made during

Chloroceryle amazona Chloroceryle aenea Anhinga anhinga Tigrisoma mexicanum Rhinoclemmys funerea Cochlearius cochlearius Aramides cajanea Crax rubra Ardea alba Chloroceryle inda Butorides virescens Mesembrinibis cayennensis Chloroceryle americana

Total recorded in 2006

Total recorded during summer

Total recorded during winter

CC2 during summer

CC1 during summer

CH3 during summer

CH2 during summer

CH1 during summer

AC2 during summer

AC1 during summer

CC2 during winter

CC1 during winter

CH3 during winter

CH2 during winter

CH1 during winter

Species

AC2 during winter

AC1 during winter

the winter phase (n=604).

1 0 14

0 0 1

0 0 3

4 3 2

8 1 22

0 0 0

0 1 1

3 8 5

0 0 0

0 0 10

0 5 0

3 0 18

0 0 0

0 0 0

13 5 43

5 13 34

18 18 77

34

8

32

1

16

3

0

59

5

39

44

18

12

0

94

176

270

13

3

55

6

8

0

0

0

0

5

0

3

3

3

85

14

99

0 0 3 13 0 8

0 0 0 2 0 1

0 0 3 0 1 23

0 0 0 4 4 7

0 0 1 0 2 38

0 0 0 0 1 4

0 0 1 0 0 0

0 0 13 5 0 11

0 0 3 0 0 0

8 3 3 0 3 8

3 5 3 3 8 13

3 0 3 0 3 15

0 3 3 0 3 0

0 3 0 0 0 0

0 0 8 19 8 81

13 14 27 8 16 47

13 14 35 27 24 128

5

0

17

3

4

1

0

5

0

0

0

0

0

0

30

5

35

3

0

3

2

3

2

0

0

0

0

8

0

0

0

8

21

Egretta caerulea Jacana spinosa Ceryle torquatus Egretta thula Heliornis fulica

11 12 4 21 7

35 9 6 0 7

5 29 3 0 5

0 3 3 0 0

18 0 5 0 0

13 0 13 15 3

13 0 0 18 3

0 0 0 0 6

0 0 0 0 3

49 32 23 33 19

333 53 61 104 58

60

47 0 9 3 8 11 4

4 0 0 0 6

84

79 0 13 3 6 12 1

27 0 0 1 1

Totals

81 0 6 43 4 17 8

37

10

64

5

33

75

51

9

3

13 28 4 21 38 71 39 60 4

241

845

Table 5-2 Adjusted number of the most common key species observed during each study phase based on Caño location, data for the summer phase has been extrapolated to take account of difference in number of surveys undertaken.

The above data (Table 5-2) shows the same data set as in Table 5-1, however for the data collected during the summer phase an extrapolation of the data has been undertaken. This extrapolation takes account of the lower number of surveys undertaken during the summer phase. Data collected within the AC sectors was multiplied by a factor of 2.6666, data collected in CH sectors by 2.57 and CC sector data was multiplied by a factor of 3. This extrapolation increases the number of total observation from 696 55

(48% of all records) to 845 records (44% of all records), the majority of these observations still remain during the winter phase (n=604). 300 Total recorded during winter Total recorded during summer

250

200

150

100

50

a Ti a gr an is hi om ng a a R m hi ex no ic cl a nu em m C m oc ys hl fu ea ne riu re s a co ch Ar le ar am iu id s es ca ja ne a C ra x ru br a Ar de C a hl al or ba oc er Bu yl e to M in rid es da es em vi br re in sc ib en is ca C s hl y or en oc ne er ns yl is e am er ic Eg an re a tta ca er Ja ul ea ca na sp in C os er yl a e to rq ua tu Eg s re tta th H ul el a io rn is fu lic a

ae ne

An hi ng

er yl e or oc

C hl

C hl

or oc

er yl e

am

az on

a

0

Figure 5-1 Variation in most common key species recorded based on study phase in all Caños. Data after extrapolation.

Figure 5-1 illustrates the variation over the total study site demonstrating the significant difference in the number of records for certain species obtained during the summer and winter phases. Figure 5-2 illustrates the variation in species composition and abundance within the Access sectors during both survey periods. Of the 18 key species observed which were identified as being common during either the winter, summer or during both phases, three were consistently absent from the AC sectors: Boat-billed Heron (Cochlearius cochlearius), Gray-necked Wood-Rail (Aramides cajanea), Green-and-Rufous Kingfisher (Chloroceryle inda).

56

or oc er yl

C hl

e am az or on oc a er yl e a en An ea hi ng Ti a gr an is hi om ng a a m R ex hi no ic an cl em um m C ys oc hl fu ea ne riu re a s co ch l ea Ar am riu s id es ca ja ne a C ra x ru br a Ar de a C al hl ba or oc er Bu yl e to in M rid da es es em vi br re in sc ib en is s ca C hl ye or nn oc en er si yl s e am er ic Ja an ca a na sp i no C er sa yle to rq ua tu s Eg re tta th ul H a el io rn is fu lic a

C hl

C hl or oc er yl e am C hl az or on oc a er yl e a An en hi ea ng Ti a gr an is hi om ng a a R m hi e xi no c cl an em um C m oc ys hl fu ea ne riu re s a co ch Ar le a am riu id s es ca ja ne a C ra x ru br a Ar de a Ch al lo ba ro ce ry Bu l e t M or in es id da es em vi br re in s ib ce is ns ca C hl ye or nn oc en er si yl s e am er ic Eg an re a tta ca er Ja ul ea ca na sp in C os er yl a e to rq ua tu Eg s re tta th H ul el a io rn is fu lic a

70 Total AC winter

60 Total AC summer

50

40

30

20

10

0

Figure 5-2 Variation in most common key species recorded based on study phase and Access (AC)

Caño only. Data after extrapolation.

120

100 Total CH winter Total CH summer Total CC winter Total CC summer

80

60

40

20

0

Figure 5-3 Variation in most common key species recorded based on study phase and Caño (Harold

(CH) and Chiquero (CC) only). Data after extrapolation.

57

Figure 5-3 illustrates the variation in species composition and abundance within the Access sectors during both survey periods. Of the 18 key species observed which were identified as being common during either the winter, summer or during both phases, only Northern Jacana (Jacana spinosa) was consistently absent from both CH and CC.

90 winter summer

80

70

60

50

40

30

20

10

0 Total recorded in AC1

Total recorded in AC2

Total recorded in CH1

Total recorded in CH2

Total recorded in CH3

Total recorded in CC1

Total recorded in CC2

Figure 5-4 Variation in observed records of Little Blue Heron (Egreta Caerulea) based on study phase within all study areas. Data after extrapolation.

Little Blue Heron (Egretta caerulea) was observed in the highest numbers hence the data has been present in an independent histograme (figure 5.4). Little Blue Herons were observed in all sectors during the winter phase however was absent from AC2 and CC during the summer phase. 5.4.2.

Terrestrial Trail

During phase 4 only one additional day survey was undertaken on the terrestrial trail. During that survey one Great Tinamou (Tinamus major) and six Mantled Howler Monkeys (Allouata palliata) were recorded. In addition to the day survey, four night surveys were undertaken during this phase on the terrestrial trail. Table 5-3 presents all data collected during the night surveys.

58

Date 14/04/2006 14/04/2006 14/04/2006 14/04/2006 14/04/2006 21/04/2006 21/04/2006 21/04/2006 26/04/2006 26/04/2006 02/05/2006 02/05/2006

Species (common name)

Species (latin name)

Little Tinamou Kinkajou Kinkajou Brown Blunt-headed Vinesnake Long-billed Hermit Brown Vinesnake Two-toed Sloth Common Opossum Red-eyed Leaf Frog Common Opossum Terciopelo / Fer-de-Lance Central American Coral snake

Crypturellus soui Potos flavus Potos flavus Imantodes cenchoa Phaethornis longirostris Oxybelis aeneus Choloepus hoffmanni Didelphis marsupialis Agalychnis callidryas Didelphis marsupialis Bothrops asper Micrurus nigrocinctus

Total # 1 1 1 1 1 1 1 1 1 1 1 1

Table 5-3 Records collected from night survey of the terrestrial trial during phase 4.

5.4.3.

Strawberry Poison Dart Frog (Dendrobates pumilio) Transects

Three surveys were undertaken during phase 4, cover three different transects. The surveys were undertaken on the 22nd April 2006 and two surveys on the 12th May 2006. All three transects were surveyed during this period and no records were obtained of D. pumilio. 5.4.4.

Assessment of visitor use of aquatic trails within the National Park

A consistent difference between the National Park data and GVI’s data was the presence of non-tourist boats recorded by GVI (table 5.4 and figure 5.5) These boats were either small wooden canoes with only a few people onboard or motorised boats that were generally travelling about the speed limit. Those boats that were assumed to be in the Park for purposes other than wildlife watching were deemed to be non-tourists.

59

Date 01/05/2006 05/05/2006 11/05/2006 23/05/2006 28/05/2006 31/05/2006 10/06/2006

Total GVI figures excl. non-tourist 37 17 14 16 19 15 16

Total GVI figures 39 19 14 16 23 16 16

Total National Park figure 33 12 14 14 15 11 15

Table 5-4 Data collected during Phase 4 on the total number of boats recorded entering the National Park. Data collected by GVI and Tortuguero National Park.

40 GVI Total National Park Total

35

30

25

20

15

10

5

0 01/05/2006

05/05/2006

11/05/2006

23/05/2006

28/05/2006

31/05/2006

10/06/2006

Figure 5-5 Data collected during Phase 4 on the total number of tourist boats recorded entering the National Park. Data collected by GVI and Tortuguero National Park.

The data collected from GVI shows that Caño Harold receives the majority of visitors, consisting of some 75% of all tourist boats. Caño Tortuguero and Caño Chiquero both receive approximately 10% each, whilst 4% of tourist boats visit both Caño Harold and Caño Chiquero (figure 5.6). 60

4% 10%

CH CC CT CH CC

11% 75%

Figure 5-6 Data collected during Phase 4 on the total number boats recorded entering the National Park. Data collected by GVI and Tortuguero National Park.

5.4.5.

Assessment of terrestrial trail condition

During this phase (10 April – 18 June) GVI counted a total of 40 points with extensions or divergences along the main trail. There were 17 extensions and 23 divergences (10 right and 13 left – see appendix F for all measurements). Up to 80% of these extensions and divergences were found between 250 m and 850 m from the zero point at Cuatro Esquinas. Due to the malfunction of the GPS under the rainforest canopy the exact location of these points could not be recorded. 5.5. 5.5.1.

Discussion Aquatic Trails

“Determination of the extent to which ecological systems are experiencing anthropogenic disturbance and change in structure and function is critical for the long-term conservation of biotic diversity in the face of changing landscapes and land use” (Canterbury et al., 2000). The ongoing purpose of this study is to assess the level of impact tourism is having on the animals within Tortuguero National Park, by identifying shifts in their distribution or abundance. This baseline study focused on counts of individual species within the specific Caños of the National Park in order to give an indication of the key species compositions found there (see table 5-1, 5-2 and figures 5-1 to 5-3).

61

It has been argued that continuous or frequent high intensity activities such as the use of motorized power boats constantly throughout the day cause more disturbance than continuous low intensity disturbance. It has also been said that in general birds appear to habituate to continual noises so long as there is no large amplitude “startling” component (Hocken et al., 1992; cited in Hill 1997). Another suggestion by Hill et al, states that most water based recreation generates medium intensity, continuous or high intensity infrequent disturbance. It is thus believed that medium disturbance may cause a site to become unattractive to the more susceptible species while the latter could result in displacement of the birds for short periods. Although the species found within the various Caños are generally similar, there are a few species that do not occur in certain Caños. For example Boat-billed Herons, Grey-necked Wood-Rails and Green-andRufous Kingfishers are not found within any of the access areas and Northern Jacana has not been recorded within either Caño Harold or Caño Chiquero. The variation in species composition between seasons is an important factor to assess when

examining

impact.

For

example,

Bare-throated

Tiger-Heron

(Tigrisoma

mexicanum) was recorded 94 times during the winter phase compared to 176 in the summer phase. The Little Blue Heron was recorded 284 times in the winter phase but only 49 times during the summer phase 4. These two species were the most commonly recorded in their respective peak season (see Table 5-2 for more detail on species composition during the study phase). Many of the species included within the key species list are migratory species and environmental factors outside of Tortuguero could potentially have an impact on the local population. If a change in these species populations is observed it would be vital to investigate the condition of other populations throughout the species range prior to any assumption being drawn in connection to the National Park.

4

Data for the summer phase has been extrapolated to take account of difference in number of

surveys undertaken.

62

From our current data we can surmise that the majority of aquatic bird activity is based on Caño Harold (Figure 5.3). Caño Harold is one of the more active Caños attracting more visitors than Caño Chiquero (see section 5.4.4).

Due to the 5km speed limit within the Park’s boundaries we can concur with the ideas of Hocken et al (1992; cited in Hill 1997) in that on this Caño there are continual low intensity disturbances. The impact of this type of disturbance is at present unclear, however it could potentially explain the high diversity of species found within the Caño. There is however a need to identify both intolerant and tolerant bird species from those ubiquitous ones which are widely found throughout disturbed and undisturbed habitats and finally generalists which are adaptable to multiple habitats. It is plausible at this stage to assume that the most common key species are either tolerant or generalist species. The way of confirming this will be through a combination of field experience, local knowledge and by undertaking an extensive and time consuming literature review. This process is necessary in order to establish a methodology for assessing disturbance based on sound scientific findings (Hill & Hamer, 1998).

When estimating the severity and likely impact of disturbance to birds the following factors should be taken into account: •

Intensity of disturbance

•

Duration and frequency (continuous, infrequent, regular, variable)

•

Seasonal variation in sensitivity of affected species

•

Presence of people associated with source

•

Whether birds move away, but return after disturbance ceases

•

If regional numbers are affected

•

If there are alternative available habitats nearby

•

If rare, scarce or shy species are affected

Adapted from Hill et al., 1997.

Future recommendations when evaluating birds as indicators of condition is the development of indices of bio-integrity whereby ecological information is related to 63

pattern of bird species, guilds or assemblages to the availability of habitat, degree of fragmentation and amount of human disturbance in a region (Bryce and Hughes, 2002). This index was developed to provide a broad based indicator of the extent to which a bird community has been affected by disturbance, rather than to describe the use of habitat by individual bird species (Canterbury et al, 2000). A key requirement for this approach is the ability to quickly and accurately estimate relative abundance of each species in a relatively diverse species assemblage at each site sampled (Bradford et al, 1998). Initial criteria for evaluating metrics as potential indicators of biological integrity include: •

Sampling is easy to conduct

•

Metrics are responsive to stressors of concern

•

Metrics are applicable over a large geographic area

•

Metrics have sufficiently high signals/noise ratio to at least be able to distinguish between sites know to be minimally and maximally impacted by a stressor

Adapted from Bradford et al., 1998 The data currently available from this study could be used as an indication of normality. For example Caño Harold should contain a certain selection of species in normal conditions at specific times of the year (see figures 5-3 and 5-4). If the composition of the species is seen to change drastically then there may possibly be a change in the environmental conditions. However isolating or even confirming these changes could potentially be both expensive and time consuming. A comprehensive review of the literature relating to the study species could potentially highlight some life history traits that would indicate species environmental variables. If such variables were identified then this would help lend support to the use of the study species as bio indicators. Data on non-avian species collected to date has been deemed unsuitable for analysis as the methodology used does not enable an assessment of the abundance and/or diversity of such species.

64

In order to assess these other groups a comprehensive review of current methodology will have to be undertaken and suitable survey techniques designed. It will not be possible to undertake multi group surveys therefore a much higher level of field work will be required to achieve the required results. Using incorrect or unsuitable survey methods can prove to significantly underestimate populations. A study of crocodilians showed that surveys undertaken during daylight hours underestimated population sizes recording only 23% of crocodilians present (Graham, 1987). It is recommended that until a more stringent assessment method is identified that the surveys are continued but at a minimal level only recording avian species. It is recommended that Caño Harold is surveyed a minimum of twice a month and Caño Chiquero once a month. Strengths of the project include frequent visitation to the sites resulting in adequate replication for data analysis, adaptation of methodology to fit with new findings and increased knowledge of local ecological systems. 5.5.2.

Terrestrial Trails

As with the data collected on the aquatic trails, the data collected on the terrestrial trails is of limited use in assessing tourist impact due to the associated complexities. In order to ascertain the impact tourists are having on the local wildlife a more specific study may be appropriate. The data from past phases has not been incorporated into this report as changes in protocol have meant the comparison of between data sets is of limited use. Further to this, until such a time that the data collection process identifies a clear aim and methodology, individual phase data should be seen as part of the developmental stage of a long-term monitoring programme. Due to the species present within the terrestrial trails study area (i.e. forest birds) accurate abundance assessments and population estimates are difficult to gain. It can be assumed that with an increase in visitor numbers the area of disturbance adjacent to the paths will increase to a point. Due to the relatively low density of paths within the National Park this increased impact on the local wildlife may be deemed acceptable. Controlling visitor numbers based on trail erosion and widening is potentially an easier and more practical impact monitoring method. However, if there is concern for a particular species, family or group within the study area then a specific research project 65

could be designed to assess tourist impact. This study could examine densities, flight initiation distances or sensitivity to disturbance. In order to initiate such a study an indepth literature review would need to be undertaken. 5.5.3.

Strawberry Poison Dart Frog Transects

The Strawberry Poison Dart Frog transects have been surveyed for three phases, during which there have been no confirmed records of any individuals within the study area. It is now assumed, based on the current data, that it can be confirmed that no Strawberry Poison Dart frogs are located within the area directly around the surveyed transects. It appears unlikely that there are any individuals within the study area. It is possible that there are small populations located within the study area which have not been identified during the transect surveys. If further surveys are desired it is recommended that a change in methodology is adopted, potentially taking a random sampling using quadrates in place of transects. During this study no attempt has been made to assess potential reasons for the absence of Strawberry Poison Dart frogs, but a comprehensive study assessing potential causes could be undertaken.

If this is required a project proposal would be produced

incorporating a full literature review. 5.5.4.

Assessment of visitor use of aquatic trails within the National Park

During Phase 4 the first Assessment of visitor use of aquatic trails within the National Park was undertaken. The results of the survey indicate that there is a difference in the numbers of boats recorded entering the Park by the National Park and the data collected by GVI (see table 5.4 and figures 5.5 & 5.6). However, if comparing the totals of tourist boats only (GVI data) to the totals of the National Park, the difference is smaller than comparing the totals of all boats recorded by GVI. In this way an average of three additional tourist boats was recorded each survey compared to the data collected by the National Park. In spite of this, more data is required to increase the data set and enable statistical analysis and it is thus recommended that further surveys are undertaken during the following phase (July – 66

September) to help establish a true pattern of the variation in perceived and actual number of boats entering the National Park. Although previous surveys have been undertaken over a 12 hour period, it appears that a six hour period would also be feasible (0600-1200 or 1200-1800) in future surveys. Interestingly, GVI also observed a certain number of boats entering more than one Caño (n=3, see figure 5.5). This is data which the National Park does not gain access to since only one Caño per tourist boat is reported to the Park. With further surveys, there may be a significant difference in the perceived and actual numbers of boats using the various Caños which should be considered in statistical analysis and future management of the Park. 5.5.5.

Assessment of terrestrial trail condition

Unfortunately, we did not use tags to mark the exact location of the extensions and divergences along the trail due to aesthetics and to the malfunctioning of the GPS. To compare the data over time the exact location through GPS and tags or markers is needed. In spite of this, the data shows that the most urgent places to install elevated trails or improved trail markers was between 250 m and 850 m from the zero point at Cuatro Esquinas where more than 80% of divergence and extensions . Example photos of divergences and extensions can be found in the Appendices. If the National Park decides that improvement of the terrestrial trail Sendero Gavilán is a high conservation priority, then GVI is prepared to assist in both the planning, development and construction of an improved terrestrial trail in order to minimize tourist impact. 5.5.6. •

Summary included in report to National Park

Surveys to date have shown that certain avian species are common within specific canals.

•

Methodology currently being used is not suitable for non avian species. If information on these species is desired new methodology will be required.

•

Continued study of tourist impact would require the development of an index of biointegrity. 67

•

Identification of key species of concern should be developed for the Gavilan Trail in order to directly assess the impact tourists are having on the area.

•

No Dendrobates Pumilio have been recorded during the course of the study. Future work would require new methodology and aims.

•

Variation in perceived and actual tourist numbers has been recorded from the aquatic trails.

•

Continued data collection will help to identify were the variation is occurring and to what extent.

•

Area requiring management on the Gavilan trail have been identified. GVI is able to assist with maintenance or improvement of the trail if required.

6.

TOURIST IMPACT SURVEY CAÑO PALMA

6.1.

Introduction

Caño Palma canal is located within the Barra Colorado Wildlife Refuge, immediately north of the river Petenencia, about 7 km northwest of Tortuguero village and National Park. Although not part of the National Park, this caño is included in the Management Plan for Visitors as it provides a suitable alternative for wildlife viewing to the National Park and thus helps to reduce the demand on the other caños (Bermúdez & Hernández, 2004). Proposed restrictions on the number of boats allowed into the National Park are due to be put in place at the end of April 2006. This is likely to increase the number of tourist boats using Caño Palma, and baseline data before this occurs is thus necessary. The processes currently taking place with the Tourist Impact surveys for the National Park have a direct effect on this study. For further information on the literature review and recommendation for the future of this study see section 5 (Tourist Impact Assessment project) of this report. 6.2.

Aims

GVI continues to undertake the Tourist Impact survey on Caño Palma in order to estimate the intensity of the tourist activity and assess any change to species

68

composition which could be directly related to the change in volume of usage on the Caño. 6.3. 6.3.1.

Methods Aquatic Trails

The methodology for the aquatic survey on Caño Palma follows exactly that used within the National Park; this includes recording the same study species (see section 5.3.1 for detailed methodology). The study area for this survey starts 500 metres north of the Biological Station on Caño Palma and continues up the Caño for 4,000 metres. The study site has been divided into four sections, they are: •

CPA1:

500 – 1,500m north of EBCP

•

CPA2:

1,500 – 2,500m north of EBCP

•

CPA3:

2,500 – 3,500m north of EBCP

•

CPA4:

3,500 – 4,500m north of EBCP

6.3.2.

Boat Dock Survey

The Boat Dock Survey is commenced at 06:00 and continues for 12 consecutive hours. During the survey data is collected on all boats passing the boat dock of the biological station. For each craft observed the following data is collected: •

Time of observation

•

Whether the boat was used by tourist

•

Number of passengers/tourists on each boat

•

Boat name and/or number

•

Boat direction

•

Time spent on canal

•

Engine type

Any additional information that is considered to potentially be of use at a later date is recorded in notes.

69

6.4.

Results

6.4.1.

Aquatic Trails

A total of seven Caño Palma Tourist Impact surveys were undertaken during Phase 4. During the surveys a total of 14 avian study species were observed (see figure 6.1). Of these species the top six most common species accounted for 64% of the species observed.

8

7

6

5

4

3

2

1

0 Gr eat

American Great Blue

Cur assow

Pygmy

Heron

Great Tinamou

Kingf isher

Bare-

Cat t le

Green

Gr een-

Ringed

Yellow-

Tiger-

t hr oat ed

Egr et

Kingf isher

backed

Kingf isher

cr owned

Her on

Tiger -

Nort hern Ruf escent Jacana

Heron

Heron

Anhinga

Gr een Ibis

Night Heron

Figure 6-1. Key species recorded during surveys of the Caño Palma study site.

6.4.2.

Boat Dock Survey

Eight Boat Dock Surveys were undertaken during Phase 4. The majority of boats recorded were non tourist boats (n=82), tourist boats accounted for 46% (n=70) of all traffic recorded during the surveys. 6.5. 6.5.1.

Discussion Aquatic Trails

As with the data collected in the National Park, the data from Caño Palma will require further analysis and greater detail obtained on the species before assumptions can be drawn on the effects tourist activity is having on their behavior. 70

6.5.2.

Boat Dock Survey

The Boat Dock Survey is currently providing a base line dataset. Although the data collected to data provides little use for in depth analysis it is providing an important dataset that can be closely examined over the next few years. With increased restriction in the National Park it is assumed that tourist traffic will increase and therefore have an impact on local species. As Caño Palma has had rare and sensitive species recorded on it this increase in tourist presences could be significant and therefore require management. The work being undertaken through the Boat Dock Survey will help to monitor this impact.

7.

COMMUNITY WORK

7.1.

Introduction

People of different nations increasingly utilize English as a common language in order to communicate with one another. Costa Rica, and in particular Tortuguero, hosts a growing number of international visitors each year. The people living in this area rely heavily on the international community and the tourism market. Acquisition of English language skills is one tool for accessing this market. 7.2.

Aims

The following are the main aims of the teaching programme: I. Local community training/capacity building. II. Increase sustainable revenue to the local communities. III. Generate local community commitment to environment conservation and sustainable development. IV. Language and Cultural Exchange.

V. Provide authentic opportunities for local students to practice listening and speaking English with native speakers.

VI. Provide an introductory course in the methodology of TEFL for Expedition Members.

71

7.3. 7.3.1.

Method Expedition Member training

All Expedition Members received fundamental training in teaching English as a foreign language utilizing the ‘Introduction to TEFL’ course adapted by GVI from the theory and methods used by TEFL (Teaching English as a Foreign Language). Theory sessions were initiated in the first week and continued through out the course of the ten weeks. The first sessions included introductory pedagogy and learning the mechanics of creating a lesson plan. Before entering the class room the student teachers (Expedition Members) conducted a mock teaching session. The teachers were then placed with a class and English lessons were launched in the second week. Expedition members were encouraged to dive into teaching soon after arrival because theory and pedagogy make more sense in the context of the classroom. The ongoing ‘Intro to TEFL’ workshops included topics such as curriculum, lesson plans, motivational strategies, cooperative learning groups, and assessment tools to accommodate a wide range of learning styles and abilities. The teachers worked in pairs so that they could dialog together about each lesson. Reflection sheets were used as a guide to begin the process of debriefing, improving, and ascertaining of what procedures worked. 7.3.2.

Teaching

The English lessons were created, written and adapted to fit the proficiency, the desired content, and the comfort level of the students and the teachers. Preparing and teaching in teams of two, Expedition Members had the opportunity to share ideas and work together. Each pair of teachers had a group of 2-5 students, who had comparable language skills. Planning took place in the afternoons and teaching in the evenings. The lessons focused more on speaking, listening, and pronunciation skills rather than on written work. GVI conducted English lessons in the San Francisco Community Primary School for children and adults. Each Monday and Thursday, for nine weeks, lessons began at 3 pm for children and at 7 pm for adults, and lasted for one hour. During these nine weeks,

72

simultaneous Language / Cultural exchanges, or Inter-cambios, were scheduled in San Francisco, at Cabinas Vista al Mar and with the Tortuguero National Park Rangers. 7.4.

Results

A total of twenty-three expedition members and staff participated in English teaching and language Inter-cambios. Thirty children and thirty-five adults were served for a total of 32 formal classroom contact hours and 15 informal Inter-cambio exchange hours. The average teacher: adult student ratio was 1:2 and average teacher: child student ratio 1:4. GVI has continued the commitment to offer the adult English language programme in San Francisco during Phase 4, as well as upholding our dedication to the children’s programme and supporting the national curriculum and the local primary school. During Phase 4 GVI continued the Inter-cambio programme with a total of 5 people from either San Francisco, Cabinas Vista al Mar or the National Park. 7.5.

Discussion

Phase 4 ended with the successful completion of 47 teaching contact hours among a total of 23 GVI teachers and 65 students. The atmosphere was relaxed and fun, but the participants worked very hard and are extremely grateful to GVI for receiving the lessons. The lessons were given and received with great enthusiasm. When polled, our students overwhelmingly responded that their reason for learning English is to help them obtain jobs in the tourism industry. Students are keen to learn English and thus increase personal capacity building in order to improve chances of getting work or a better job within the thriving tourism of Tortuguero. The community of San Francisco is also generally interested in GVI’s presence and work in the area, and the meetings have built friendships and mutual respect. However, we recommend that in future the classes are offered in two 4-week sessions. Commencing classes often and the starting up of novice classes each time should promote greater participation than joining a class already in session.

73

8.

Bibliography

Autar, L. 1994. Sea turtles attacked and killed by Jaguars in Suriname. Marine Turtle Newsletter 67:11-12. Azevedo-Ramos, C. De Carvalho, O. JR. Nasi, R. (2002) Animal Indicators, a Tool to Assess Biotic Integrity After Logging Tropical Forests? Núcleo de Altos Estudos Amazônicos, Report: 1-35. Bjorndal, K.A., Wetherall, J. A., Bolten, A. B., & Mortimer, J. A. 1999. Twenty-Six Years of Green Turtle Nesting at Tortuguero, Costa Rica: An Encouraging Trend. Conservation Biology 13 (1): 126-134. Blumstein, D. T., Fernandez-Juricic, E., LeDee, O., Larsen, E., Rodriiguez-Prieto, I. & Zugmeyer, C. 2004. Avian Risk Assessment: Effects of Perching Height and Detectability. Ethology 110, 273-285. Blumstein, D. T., Fernandez-Juricic, E., Zollner, P. A., and Garity, S. A. 2005. Interspecific variation in avian responses to human disturbance. Journal of Applied Ecology 42, 943-953. Boza, M.A. (1993). Conservation in Action: Past, present and future of the National Park System of Costa Rica. Conservation Biology 7 (2): 239-247. Bradford, D.F., Franson, S.E., Neale, A.C., Heggem, D.T., Miller, G.R. and Canterbury, G.E. (1998). Bird species assemblages as indicators of Biological Integrity in Great Basin Rangeland. Environmental Monitoring and Assessment 49: 1-22. Bryce, S.A. and Hughes, R.M. (2002). Development of a Bird Integrity Index: Using Bird Assemblages as Indicators of Riparian Conditions. Environmental Management 30 (2): 294-310. Canterbury, G.E., Martin, T.E., Petit, D.R, Petit, L.J, and Bradford, D.F (2000). Bird communities and habitat as ecological indicators of forest condiditons in regional monitoring. Conservation Biology 14 (2): 544-558.

74

Chacón, D., Valerín, N., Gamboa, H. & Marín, G. (1999). Manual de mejores prácticas de conservación de las tortugas marinas en Centroamérica. p.19. De Haro, A. & Troëng, S. 2005. Report on the 2005 Green Turtle Program at Tortuguero, Costa Rica. Unpublished reported presented to Caribbean Conservation Corporation. 49 pp. Fernandez-Juricic, E., Venier, M. P., Renison, D., & Blumstein, D. T. 2005. Sensitivity of wildlife to spatial patterns of recreationist behaviour: A critical assessment of minimum approaching distances and buffer areas for grassland birds. Biological Conservation. 125, 225-235. Gill, J.A., Sutherland, W.J and Watkinson, A.R. (1996). A method to quanify the effects of human disturbance on animal population. The Journal of Applied Ecology 33 (4): 786792. Gill, J.A., Norris, K. and Sutherland W.J. (2001). The effects of disturbance on habitat use by Black-Tailed Godwits Limosa limosa. The Journal of Applied Ecology 38 (4): 846856. Graham, A.D. 1987. Methods for surveying and monitoring crocodiles. In: Hutton, J.M., J.N.B. Mpande, A.D. Graham and H.H. Roth (eds). Proceedings SADDC Workshop on management and utilization of crocodiles in the SADDC region of Africa, 74-101. Hill, D. Hockin, D. Price, D. Tucker, G. Morris, R. and Treweek, J. (1997). Bird disturbance; Improving the quality and utility of disturbance research. The Journal of Applied Ecology 34 (2): 275-288. Hill, J.K. and Hamer, K.C. (1998). Using species abundance models as indicators of habitat disturbance in tropical forest. Journal of Applied Ecology 38: 458-450.

IUCN (2003) 2003 IUCN Red List of Threatened Species. IUCN, Gland, Switzerland [http://www.redlist.org, accessed 2 February 2004].

75

Laiolo, P. 2003. Diversity and structure of the bird community overwintering in the Himalayan subapline zone: is conservation compatible with tourism? Biological Conservation. 115, 251-262. Miller, C. M. 2001. Measurement of Jaguar Tracks: a promising means to identify individuals. Track Collection Protocols, Belize. Preisler, H. K., Ager, A. A., & Wisdom, M. J. 2006. Statistical methods for analyzing responses of wildlife to human disturbance. Journal of Applied Ecology. 43, 164 – 172. Rabinowitz, A. R., Nottingham Jr., B. G. 1986. Ecology and behaviour of the jaguar (Panthera onca) in Belize, Central America. Journal of Zoology 210, 149–159. Rodriiguez-Prieto, I. & Fernandez -Juricic, E. 2005. Effects of direct human disturbance on the endemic Iberian frog Rana iberica at individual and population levels. Biological Conservation. 123, 1-9. Rutschke, E., 1987. Waterfowl as bio-indicators. In: Diamond, A.W., F.L. Filion (eds), The value of birds. ICBP Technical Publication No. 6. 167–172. Sanderson, E. W., Redford, K. H., Chetkiewicz, C. B., Medellin, R. A., Rabinowitz, R. A., Robinson, J. G. & Taber, A. B. (2002) Planning to save a species: the jaguar as a model. Conservation Biology, 16, 1–15. Silver, S. C., Ostro, L. E. T., Marsh, L. K., Maffei, L., Noss, A. J., Kelly, M. J., Wallace, R. B., Gómez, H., and Guido Ayala. 2004. The use of camera traps for estimating jaguar Panthera onca abundance and density using capture/recapture analysis. Oryx 38 No 2, 148-154. Troëng, S. 2000. Predation of green (Chelonia mydas) and Leatherback (Dermochelys coriacea) turtles by Jaguars (Pantera onca) at Tortuguero National Park, Costa Rica. Chel. Cons. Biol. 3 (4):751-753. Troëng, S., Chacón, D. & Dick, B. (2004). Possible decline in Leatherback Turtle Dermochelys coriacea nesting along the coast of Caribbean Central America. Oryx, 38 (4), 395 - 403. 76

Troëng, S. & Rankin, E. (2005). Long-term conservation efforts contribute to positive Green Turtle Chelonia mydas nesting trend at Tortuguero, Costa Rica. Biological Conservation, 121, 111 - 116 Widdowson, B & Widdowson, G. 2004. Checklist to the Birds of Tortuguero, Costa Rica. Whitman, A. A., J. M. Hagan and N. V. L. Brokaw. 1998. Effects of selection logging on birds in northern Belize. Biotropica 30:449-457.

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9.

APPENDIX

Appendix A – Seasonal nesting distribution of leatherbacks, green, hawksbill and loggerhead turtles on the North Beach between March and Mid June 2006.

7 Half Moon Nest

6

5

4

3

2

1

78

6/ 06

15 /0

6/ 06

08 /0

6/ 06

01 /0

5/ 06

25 /0

5/ 06

18 /0

5/ 06

11 /0

5/ 06

04 /0

4/ 06

27 /0

4/ 06

20 /0

4/ 06

13 /0

4/ 06

06 /0

3/ 06

30 /0

3/ 06

23 /0

3/ 06

16 /0

3/ 06

09 /0

02 /0

3/ 06

0

Appendix B – Spatial nesting distribution of leatherbacks, green, hawksbill and loggerhead turtles on the North Beach between March and Mid-June 2006. 8 nest

1/2 moon

7 6 5 4 3 2 1

79

3

2 2. 12 5 2. 25 2. 37 5 2. 5 2. 62 5 2. 75 2. 87 5

1 1. 12 5 1. 25 1. 37 5 1. 5 1. 62 5 1. 75 1. 87 5

0. 25 0. 37 5 0. 5 0. 62 5 0. 75 0. 87 5

0

Appendix C – Study Species for Tourist Impact Study Common Name

Scientific Name

Rufescent Tiger-Heron Bare-throated Tiger-Heron Agami Heron Tricolor Heron Great Blue Heron Great Egret Snowy Egret Little Blue Heron Cattle Egret Green Heron Yellow-crowned Night-Heron Boat-billed Heron Osprey Ringed Kingfisher American Pygmy Kingfisher Belted Kingfisher Green Kingfisher Amazon Kingfisher Green and Rufous Kingfisher Green Ibis Purple Gallinule Northern Jacana Gray-necked Wood-Rail Sungrebe Great Tinamou Little Tinamou Crested Guan Great Curassow Anhinga Neotropic Cormorant Great Tinamou Little Tinamou Crested Guan Great Curassow White-faced Capuchin Spider Monkey Mantled Howler Monkey Neotropical River Otter West Indian Manatee Black River Turtle Spectacled Caiman American Crocodile Strawberry Poison Frog

Tigrisoma lineatum Tigrisoma mexicanum Agamia agami Egretta tricolor Ardea herodias Ardea alba Egretta thula Egretta caerulea Bubulcus ibis Butorides virescens Nyctanassa violacea Cochlearius cochlearius Pandion haliaetus Ceryle torquata Chloroceryle aenea Ceryle alcyon Chloroceryle americana Chloroceryle amazona Chloroceryle inda Mesembrinibis cayennensis Porphyrio martinica Jacana spinosa Aramides cajanea Heliornis fulica Tinamus major Crypturellus soui Penelope purpurascens Crax rubra Anhinga anhinga Phalacrocorax brasilianus Tinamus major Crypturellus soui Penelope purpurascens Crax rubra Cebus capucinus Ateles geoffroyi Allouata palliata Lutra Longicaudis Trychechus manatus Rhinoclemmys funerea Caiman crocodilus Crocodylus acutus Dendrobates pumilio

80

Appendix D – Breeding Evidence

81

Appendix E – Weather Data

CC

10-

26-

51-

76-

90-

<10%

25%

50%

75%

90%

100%

1

2

3

4

5

6

N

L

M

H High

Leaf Light

drip (N-

leaf

drip, Medium leaf drip, leaf

heard/seen light heard/seen

L-M-H)

drops every few fairly

large like

seconds

constant drops

D

M

W

Ground

Dry, no sign of Moist, ground is

state

ground moisture, clearly wet with Wet, ground is

(Dry,

probably

Moist,

rained for several areas of standing areas of standing

Wet)

days

water

water

N

L

M

Rainfall

small wet,

drip,

drip

is

as constant, sounds

No leaf drip

hasn't some

leaf

there

is

heavy rain

frequent

H

Light rainfall, dry

(None,

patches

Low,

of Medium, clothes High,

clothes will still become

Medium,

be evident after within

High) No rainfall

some time

minutes

82

clothes

wet become soaking a

few wet instantly

almost

Appendix F – Map of Caños in Tortuguero National Park

Note: The names of Caños have changed since production of this map. Thus Caño Mora is now Caño Harold and Caño Muerto is now Caño Mora.

83

Appendix G – Photo examples of divergences and extensions

Divergence to the

Divergence to the

left

right

Extension Extension

84

Appendix H – Total measurements of divergences and extensions

Main

Centre

Up

Down

Entrance

Exit

Divergence

Distance

width

(1m)

(1m)

width

width

length

from trail

Extension 1

371

318

331

Divergence right 2

113

911

309

Extension 3

362

282

344

703

Extension 4

372

339

390

473

Divergence right 5

157

350

tree

Divergence right 6

90

98

110

590

361

tree

Divergence right 7

85

85

75

1130

1175

350

Divergence left 8

140

350

160

737

745

200

Extension 9

390

380

380

527

Extension 10

380

440

350

550

Divergence right 11

120

990

210

2450

2730

600

Divergence left 12

200

40

330

1460

1560

300

Divergence right 13

70

140

160

480

270

tree

Divergence right 14

150

330

210

1050

900

tree

Extension 15

375

Divergence right 16

130

140

160

480

270

tree

Divergence right 17

113

110

116

1037

1147

184

Divergence left 18 a

278

202

383

900

753

tree

Extension 18 b

463

Divergence left 18 c

84

84

157

1402

1493

bushes

Divergence left 19

247

83

210

1137

1341

210

Extension 20

453

Divergence left 21 a

90

1080

200

Extension 21 b

540

Divergence left 21 c

143

190

322

866

795

150

Divergence right 22

75

243

309

715

683

200

Divergence right 23 a

73

246

300

468

479

90

Extension 23 b

380

203

204

807

Divergence left 24 a

150

137

103

2934

2056

250

Divergence left 24 b

85

212

60

1255

1258

200

497

386

373

214

400

355

900

372

1380 63

425

403

820

500

64 477

length 356

292

310

trail

1150 1262

85

Extension 24 c

520

493

470

197

203

Extension 25

629

460

657

Extension 26

516

435

463

472

175

714

Extension 27

103

380

310

162

173

505

Extension 38 a

473

430

543

Divergence left 28 b

52

Extension 28 c

464

364

Divergence right 29 a

45

102

Extension 29 b

217

178

Divergence right 29 c

97

886

632 108

95

381

290

586

200

913

90

633 150

252

1024

227 66

86

377 562

163

325

357