Tracking The Vanishing Frogs

Tracking the Vanishing Frogs

Tracking the Vanishing Frogs An Ecological Mystery Environmental Science Max L. Costner Tracking the vanishing frogs is an entertaining excursion into the plight of the disappearance of a once common amphibian. The author is the narrator rather than a participant in evaluating the research. Kathryn Phillips followed the biologists through marshes and other land conditions and details the efforts of several Herpetologists in their attempt to locate and explain the disappearance of frog and toad species. In the search biologists visit California and Costa Rica looking for the California red-legged frog and the arroyo toad. Though this book mainly discusses specific species of frogs and toads the phenomena of disappearing amphibians also include salamanders and newts. Herpetology is the scientific study of amphibians and reptiles. It has been noted in the history of Herpetology literature of what appear to be the decline of amphibians like frogs and salamanders. However, it was not until the late 1980’s that Herpetologists from many different parts of the world reported declining populations of amphibians. The decline was not only reported in areas where ecosystems were destroyed because of human intervention. The declines were also reported from areas that were protected such as national parks and nature preserves. Amphibians are believed to have appeared on earth around 350 million years ago when the earth’s physical features were different. There was one large land mass and one ocean that encompassed most of the surface volume as water still does today. It is thought amphibians evolved from two or more Osteichthyes which is a class of bony fish with a vertebrate. Over time amphibians evolved from one group into three smaller groups or orders. One order of amphibians is the Gymnophiona which include caecilians which are wormlike and live underground or under leaf cover. They are a species that are not widely studied but there are about 160 known species. A second order is called Caudata and includes newts and salamanders. These amphibians look like lizards but have scale less bodies. The last order is called Anura which are frogs and toads. They are the most abundant type of amphibian and have about 3,960 species. They are estimated to have evolved 150 to 200 million years ago from the main amphibian lineage. The difference between frogs and toads is unspecified. However, toads are better at surviving in drier conditions and they have poisonous glands. Contrary to popular myth handling toads are not a cause of warts. Toads are considered a variety of frogs; however, frogs are not a variety of toads. The first search was for the Costa Rica Gold which is a toad species. They are famous for their appearance and used in advertisements to promote tourism in spite of their brief appearance. They only live in a few spots in the forest above the town of Monteverde. The males are bright orange, but the females are the opposite in appearance. They are bigger in size and are dark olive to black skinned with a speck of orange. They breed only a few weeks during the spring usually in April when the weather conditions are rainy and windy. The breeding period lasts only a week to ten days and the females lay two to four hundred eggs. Afterwards the species seem to disappear probably burrowed into the earth. The biologists investigating these toads could not find hardly any in 1989. The area was a preserve so the causes for their disappearance were thought to be human

exploitation for pets, new predators, and ozone layer depletion. The next search involved a frog named the California red-legged. It is one of two types of red-legged frogs in California. They are large in size and measure four to five inches long. They are measured by the distance between their noses to their posterior. Their colors range from gray-green, brown, and redbrown and they usually have spots on their backs. They were once the most abundant frogs in that state. They consume beetles, water bugs, snails, spiders, and the occasional mouse. Like many frog species the red-legged are sought for their legs as food. Literature from as far back as the early 1800’s describes their commercial value for restaurants. Other reasons for their declining numbers are because of habitat destruction of marshlands in part by people trampling them in order to search for frogs. They were also drained because of the belief that they were the cause of malaria. Other reasons were to make land available for irrigation, major dams and water projects, as well as for farmlands. Frogs are a diverse amphibian and do not all reproduce the same way. The most common method is the female laying eggs in a pond or stream and the male fertilizing them. Then they hatch into tadpoles that develop into frogs. However, the glass frog so called because its skin is transparent lays its eggs on the under sides of leaves so that when they hatch they fall into the water below. The Dendrobatid poison-dart frog, which has a toxic skin, lays its eggs in leaf litter on a moist forest floor. The most unusual method is accomplished by the gastric brooding frog. It carries its eggs in its stomach where they hatch and at the right time are regurgitated out of the mother’s mouth fully formed. The reasons for the decline and disappearance of Anura amphibians are multiple, but some are debatable. The desire to possess living things as pets by humans cannot be overlooked. Many species of frog’s legs have been used for food for centuries. At one time they were an inexhaustible resource for harvesting, and are still palatable for many today. Many countries are harvesting their frog population to extinction. Frog farms have been attempted but have failed because frogs do not breed well in captivity. The conditions have to be right or frogs do not seem interested in breeding. Additionally, frog and toad skins are used to produce purses, wallets, and other products. Habitat destruction is another reason why amphibians are disappearing. As mentioned this occurs because of farming and water projects. Other reasons for habitat destruction are to make land available for cattle grazing, logging, housing, and parking lots. Recreational activities like mountain and dirt biking, and boating often interfere with amphibian ecosystems and breeding grounds. Even preserved areas are sometimes ignored for personal pleasure. Other means by which humans are causing the disappearance of amphibians is through the use of pesticides, chemical contaminants, pathogens, nitrogen based fertilizers, and introduced species. Amphibians are victims of biomagnifications which may be helping cause the widespread occurrences of deformities or malformations reported about amphibians. This has been perceived to indicate major environmental problems. The final cause is climate change. Amphibians are sensitive to changes in moisture and temperature which are affected by weather patterns. This may affect their sensitivity to chemicals, decrease immune functions, and alter breeding behavior. Global warming is debated, but is none the less considered a factor in amphibian decline. Connected to the climate is the effect that increased UV-B radiation has on amphibians. It can work synergistically with the other items listed above to slow growth rates, cause immune dysfunction, or kill amphibians directly. There are efforts by some biologists and activists to protect the declining amphibian population. One of the ways that this is being attempted is by the use of the Endangered Species Act of 1973. However, it has not been very effective. One reason is that it can be voided by the Secretary of Interior. There are many corporations with commercial interest that are critics of the act. Another

reason is that the Fish and Wildlife Service is understaffed so that requests are not filed quickly enough under federal guidelines. Also, they fail to put programs into effect that would help endangered species. Amphibians have survived two mass extinctions in which one killed the largest animals to have ever roamed the earth the dinosaurs. Now it seems like they are being driven to extinction by human animals that have had a relatively short existence span. I remember in the mid-seventies catching and releasing frogs in little steams down from larger rivers where my grandfather was casting for whatever hapless fish would try to take his bait. Years later I visited similar settings to look for frogs and noticed the absence of their presence. I did not think much about it at the time, but now I have something to think about. Bibliography Phillips, Kathryn,(1994). Tracking the vanishing frog: An Ecological Mystery. Penguin Books.