Marine Mammals

Marine Mammals Class Mammalia

Endotherms Like birds, mammals produce body heat internally through metabolism. Mammals keep their body temperature high and nearly constant by controlling their metabolism and regulating the loss of heat through the body surface.

Endothermy determines many of the capabilities of mammals Mammals can live in cold climates and be active. The rapid metabolism provides mammals with the energy to perform strenuous activities for long periods of time.

Respiratory System The respiratory system of a mammal is adapted for efficient gas exchange. The lungs are large and contain millions of aveoli, the small chambers in which gas exchange occurs.

Respiratory System Compared with the lung of a reptile, the lung of a mammal has a much larger surface area available for gas exchange. Another adaptation that contributes to the efficiency of respiration is the diaphragm, a sheet of muscle below the rib cage. Contraction of the diaphragm during inhalation helps draw air into the lungs

Hair All mammals have hair. The main function of hair is to insulate the body against heat loss. Most mammals (except humans and whales) are covered with a thick coat of hair. Hair color also serves to camouflage a mammal from predators or a predator from being seen by its prey

Completely Divided Heart Like birds, mammals have a 4 chambered heart with 2 completely separated ventricles. Separate ventricles keep deoxygenated blood from diluting oxygenated blood and allow more efficient pumping of blood through both circuits of the circulatory system

Circulatory System The structure of a mammalian heart helps to ensure the efficient flow of blood throughout the body The heart has 2 atria and 2 completely separated ventricles

Circulatory System Oxygenated blood and deoxygenated blood never mix. Recall that the heart of an amphibian or a reptile have only 1 ventricle Mammals have such a high demand for oxygen that they cannot tolerate the dilution of oxygenated blood by deoxygenated blood

Milk Female mammals produce milk to feed their offspring. Milk is a nutritious fluid that contains fats, protein, and sugars. It is produced by the mammary glands, which are modified sweat glands located on the thorax or abdomen

Single Jawbone The lower jaw of a reptile is composed of several bones, but the lower jaw of a mammal is composed of one single bone. The characteristic is particularly important for identifying mammalian fossils because many other characteristics of mammals like hair or mammary glands do not fossilize

Specialized Teeth Teeth in different parts of a mammals jaws are modified for different functions. Those at the from of the jaw are used for biting cutting, seizing prey, while those along the sides of the jaw are used for crushing, grinding or slicing.

Feeding For most mammals, the breakdown of food begins with chewing in the mouth. Other vertebrates simply swallow their food whole or in large pieces. Chewing speeds up digestion by breaking food into small pieces that can be more easily digested by enzymes

Feeding Most mammals have specialized teeth for gripping and holding food, and for chewing.

Teeth Chisel-like incisors cut.

Teeth Pointed canines grip, puncture, and tear

Teeth Premolars shear, shred, cut, or grind

Teeth Molars grind, crush, or cut

Teeth Variations in the size and shape of teeth among different mammalian species reflect differences in diet. Carnivores have completely different teeth than herbivores which are different than omnivores.

Teeth Baleen whales, such as the blue whale, do not have teeth. Instead, they have baleen, thin plates of fingernail-like material that hang from the roof of the mouth. As a baleen whale swims, it gulps huge quantities of water. Then it closes its mouth and pushes the water through the baleen. Shrimp and other small invertebrates are trapped in the baleen and then swallowed.

Nervous system The brain of a mammal is about 15 times heavier than the brain of a similarly sized fish, amphibian, or reptile. Enlargement of the cerebrum accounts for the most of this size increase because it is the largest part of the brain.

Nervous System The cerebrum’s surface is usually folded and wrinkled which greatly increases the surface area without increasing its volume. The cerebrum evaluates input from the sense organs, controls movement, and initiates and regulates behavior. It is also involved with memory and learning.

Echolocation The dolphin is able to generate sound in the form of clicks, within its nasal sacs, situated behind the melon. The frequency of this click is higher than that of the sounds used for communication and differs between species. The melon acts as a lens which focuses the sound into a narrow beam that is projected in front of the animal.

Echolocation When the sound strikes an object, some of the energy of the soundwave is reflected back towards the dolphin. It would appear that a bone in the dolphin's lower jaw receives the echo, and the fatty tissue behind it transmits the sound to the middle ear and then to the brain. It has recently been suggested that the teeth of the dolphin, and the mandibular nerve that runs through the jawbone may transmit additional information to the dolphin's brain.

Echolocation As soon as an echo is received, the dolphin generates another click. The time lapse between click and echo enables the dolphin to evaluate the distance between it and the object; the varying strength of the signal as it is received on the two sides of the dolphin's head enable it to evaluate direction. By continuously emitting clicks and receiving echoes in this way, the dolphin can track objects and home in on them.

Echolocation The echolocation system of the dolphin is extremely sensitive and complex. Using only its acoustic senses, a bottlenose dolphin can discriminate between practically identical objects which differ by ten % or less in volume or surface area. It can do this in a noisy environment, can whistle and echolocate at the same time, and echolocate on near and distant targets simultaneously - feats which leave human sonar experts gasping.

Placental Mammals Placental mammals are a diverse group that comprises at least 18 orders. 95% of all mammal species are placental mammals They live on land, in water, and in the air.

Order Pinnipedia Seals, Sea Lions, and Walruses have paddle shaped flippers and fusiform bodies for swimming, but still need to rest on land. They are predators, feeding mostly on fish and squid.

Order Pinnipedia Most pinnipeds live in cold water To keep warm, they have a thick layer of fat under their skin called blubber. Besides acting as insulation, it serves as a food reserve and helps provide buoyancy

Order Pinnipedia Pinnipeds also have bristly hair for added protection against the cold. Many of them are quite large, which also helps conserve body heat because large animals have less surface area, and therefore lost less body heat.

Family Phocidae True Seals are distinguished by having rear flippers that cannot be moved forward. On land, they must move by pulling themselves along with their front flippers. They swim with powerful strokes of the rear flippers

Family Phocidae Large eyes and nose, but lack an external ear Anterior flippers are covered with hair; five toes with sharp nails and they cannot be rotated backwards. Usually seen laying on their sides

Family Otariidae Sea Lions (eared seals) are similar to true seals except that they have external ears. They can also move their rear flippers forward, so they can use all four limbs to walk or run on land

Family Otariidae The front flippers can be rotated backward to support the body, permitting the animal to sit on land with its neck and head raised The undersurface edge is not covered with hair or nails to reduce water resistance in swimming

Family Odobenidae The walrus is a large pinniped with a pair of distinctive tusks protruding down from the mouth. It feeds mostly on bottom invertebrates, particularly clams. It was once thought that the walrus used its tusks to dig up food, but there is no evidence for this.

Family Odobenidae

Family Odobenidae Instead, these pinnipeds apparently suck up their food as they move along the bottom. The stiff whiskers of the snout act as feelers. The tusks are used for defense and to hold or anchor to ice

Family Odobenidae Walruses inhabit the Arctic seas and ice floes. They have no external ears, but can rotate their hind flippers and "walk" on land. They are set apart from other pinnipeds not only by their tusks, but also by the presence of two large air pouches, or sacs, extending from each side the pharynx (in the neck). These pouches can be inflated to hold the head above water when sleeping, or used as resonance chambers to enhance underwater sound.

Order Carnivora Carnivores generally have long canine teeth, strong jaws, and clawed toes, which they use for seizing and holding their prey. Most have keen senses of sight and smell which aid in hunting

Family Mustelidea Sea otters are the only marine member of the mustelid family, which includes such land mammals as river otters, weasels and badgers. Sea otters are the smallest marine mammals.

Family Mustelidea They do not inhabit the open ocean, instead they live among coastal kelp beds, where they dive and hunt for a variety of shellfish and marine invertebrates. With their exceptionally thick, dark fur, longer tail, lack of true flippers, and their ability to use a rock as a feeding tool, sea otters are distinguished from other marine mammals.

Family Mustelidea It also differs from other marine mammals in lacking a layer of blubber. Insulation from the cold is provided by air trapped in the dense fur. Sea otters are playful and intelligent animals. They spend most of their time in the water, including breeding and giving birth

Family Ursidae The polar bear is the second member of the order carnivora that inhabits the marine environment. They are semi-aquatic animals that spend a good part of their lives on drifting ice in the Arctic

Order Ursidae They feed primarily on seals, which they stalk and capture at the seals surface to breath or rest

Order Sirenia Sirenians have a pair of front flippers but no rear limbs. They swim with up-and-down strokes of the paddle-shaped horizontal tail. The round tapered body is well padded with blubber. They have wrinkled skin with a few scattered hairs

Order Sirenia All three species of Manatees belong to the family Trichechidae The family Dugongidae includes the dugong found in the Indian and western Pacific Oceans. A second species, the Steller's sea cow was discovered in 1741 and hunted to extinction by 1768. This species lived primarily in the Commander Islands of the western Bering Sea.

Order Sirenia Sirenians are gentle creatures who usually live in groups. They are the only strict vegetarians among marine mammals. Their large lips are used to feed on seagrasses and other aquatic vegetation

Order Sirenia Seagrass beds, their source of food are being destroyed at an alarming rate by anchor and boat damage and by excess silt and nutrients from land, which often results from deforestation and intensive farming.

Order Sirenia Humans have exploited sirenians for their meat, skin, and oil-rich blubber. Like elephants and other large mammals, they reproduce slowly, typically one calf every three years.

Order Cetacea The largest group of marine mammals is the cetaceans. Of all marine mammals, the cetaceans along with the sirenians have made the most complete transition to aquatic life

Order Cetacae The bodies of cetaceans are streamlined and look remarkably like fish. This is a dramatic example of convergent evolution – where different species develop similar structures because they have similar lifestyles

Order Cetacea Blubber provides insulation and buoyancy; body hair is practically absent. Cetacean nostrils differ from those of other mammals. Rather than being on the front of the head, they are on the top, forming a single or double opening called the blowhole

Order Cetacea Cetaceans are divided into 2 groups – the baleen whales and the toothed whales Suborder Mysticeti derived from the Greek word for moustache, mystax.

Baleen Whales Instead of teeth, they have rows of flexible, fibrous plates named baleen that hang from the upper jaws. Baleen is made of keratin. The inner edge of each plate consists of hairlike bristles that overlap and form a dense mat in the roof of the mouth.

Baleen whales The whale filter feeds by taking a big mouthful of water and squeezing it out through the bristles. The whale then licks off the food that is left behind on the bristles and swallows it.

Baleen Whales Baleen whales are not only the largest whales, they are among the largest animals that have ever lived the earth.

Family Balaenopteridae The rorquals feed by gulping up schools of fish and swarms of krill. The lower part of the throat expands when feeding

Minke Whale

Sei Whale

Blue Whale

Fin Whale

Humpback Whale

Family Eschrichtiidae Gray whales are primarily bottom feeders. When examined, their stomachs contain mostly amphipods that inhabit soft bottoms Grays stir up the bottom with their pointed snouts and then filter the sediment leaving characteristic pits on the bottom

Family Balaenidae The right whales and the bowhead whale feed by swimming along the surface with their huge mouths open. They have the largest baleen plates of the whales but the finest bristles. This allows them to filter small plankton like copepods and some krill.

Family Neobalaenidae The pygmy right whale

Suborder Odontoceti The toothed whales have teeth that are adapted for a diet of fish, squid, and other prey. They use their teeth only to catch and hold prey, not chew it.

Family Iniidae  3 Genus  very distantly related to oceanic dolphins  live in the most complex river systems like the Amazon, the Indus and Ganges, and the Yangtze.  very small to medium-sized  all have extremely long beaks, sometimes reaching one fifth of the total body length, and many pointed teeth  extremely flexible necks allow them to navigate  brains are extremely large and well developed  very small dorsal fins, often only a couple of centimeters tall

Family Monodontidae (beluga and narwhale)

2 species  this family lack a dorsal fin medium-sized whales generally found in schools, sometimes including more than 100 individuals migrate in response to the shifting ice pack highly vocal

Family Physteridae The largest toothed whale is the sperm whale. The sperm whale is now the most numerous of the great whales, even though it was the mainstay of the whaling industry for centuries.

Family Physteridae Sperm Whales are fond of squid, including the giant deep-sea ones. Undigested squid beaks and other debris accumulate in the gut as large globs of sticky material known as ambergris, an ingredient in fine perfumes

Family Ziphiidae  Beaked whales  the snout is sharply set off from the rest of the head by a bulging forehead  flippers are relatively small and oval to gently pointed in shape  have up to six short grooves on their throats.  capable of prolonged deep dives.  Males of all species have 1 or 2 large functional teeth on the lower jaw; smaller, apparently nonfunctional teeth are sometimes seen on upper and lower jaws of several species. The teeth of females of most species remain buried in the gums, suggesting that ziphiid teeth are used mostly in social encounters.

Family Platanistidae Indian River Dolphins are generally small They have a long, slender beak, above which rises a sharply differentiated, bulging forehead eyes are small The dorsal fin is low these animals probably rely on echolocation more than vision to locate their prey

Family Phocoenidae Porpoises are relatively small They have short jaws and no beak A dorsal fin is present and triangular generally occupy bays, estuaries, and inlets close to shore porpoises are relatively slow, traveling in small groups of fewer than 6 individuals

Family Delphinidae This family contains dolphins, killer whales, pilot whales, and other relatives

Family Delphinidae The killer whale, or orca is a magnificent black and white predator with a taste for seals, sea lions, penguins, fishes, sea otters, and even other whales. They use their white bellies to flash and frighten herring schools and their flukes to stun the fish

Family Delphinidae The many species of dolphins typically possess a distinctive snout, or beak, and a perpetual “smile” Playful, highly social, and easily trained, dolphins win people’s hearts.

Family Delphinidae Dolphins often travel in large groups called pods. They like to catch rides along the bows of boats or around great whales

Those Darn Humans!!!!! Whale hunting, or whaling is an old tradition with a rich history. Stone Age people hunted whales as early as 6000 B.C. Native Americans hunted gray whales in prehistoric times It was not until the 1600’s that Europeans started to substantially exploit the great whales in the North Atlantic

Whaling Americans, who eventually dominated worldwide whaling, began hunting off New England by the late 1600’s. Whales were harpooned from small open boats, a technique whalers learned from the natives.

Whaling It was a good fishery, but not just for food. Blubber provided “train oil” that was used to make soap and lamp oil. Baleen was used to make corsets and other goods. Meat and other valuable products also were obtained from the huge animals

Whaling Whaling efforts rapidly increased after fast steamships and the devastating explosive harpoon were introduced in the 1800’s.

Whaling The first to be seriously depleted was the Northern right whale. By the early 1900’s whaling had moved to the rich feeding grounds around Antarctica, where other species could be hunted.

Whaling Whaling nations developed factory ships able to process whole carcasses. The Antarctic fishery reached its peak in the 1930’s. It is estimated that over a million whales were taken from the Antarctic alone.

Whaling In 1946, 20 whaling nations established the International Whaling Commission (IWC) in an attempt to regulate whale hunting to stop overfishing. However, quotas were not enforced, and many whaling nations did not belong to the IWC

Whaling The United States Congress passed the Marine Mammal Protection Act of 1972, which bans the hunting of all marine mammals in US waters and the importation of marine mammal products. By 1974, the IWC had protected the blue, gray, humpback, and right whales around the world, but only after their stocks were no longer economically viable.

Whaling The former Soviet Union halted whaling in 1987. Japan, Iceland, and Norway decided in 1988 to continue hunting as “scientific whaling”

Whaling In 1994, the IWC created a vast sanctuary for all whales in the waters around Antarctica. Japan, however, decided to continue hunting whales in Antarctica

Good Ole Japan! Japan, however, decided to continue hunting whales in Antarctica In 1997 Norway resumed commercial whaling in the North Sea in defiance of the IWC regulations. Both countries decided that it would be in their best interest to set their “own quotas”

Swimming and Diving Seals sea lions and other pinnipeds swim by moving their flippers Sirenians and cetaceans move their tails and flukes up and down, while fishes move their tails from side to side

Swimming and diving Cetaceans have the advantage of having the blowhole on the top of their head This allows them to breath even though most of the body is underwater, although many pinnipeds and dolphins jump clear out of the water to take a breath when they are swimming fast. This also means that cetaceans can eat and breath at the same time

Swimming and diving In the large whales the moisture in their warm breath condenses when it hits the air. Together with a little mucus and seawater, this water vapor forms the characteristic spout, or blow, which can be seen at great distances

Swimming and diving Marine mammals have mastered the art of diving, and most make prolonged dives to considerable depths for food. Sea otters can dive for 4-5 minutes up to 180 ft. Pinnipeds normally dive for up to 30 minutes up to 820 ft Elephant seals are capable of dives up to 1,300 ft

Swimming and diving The weddell seal has been recorded diving for as long as 73 minutes and as deep as 1,900 ft. Baleen whales, since they are plankton feeders have no need to be deep divers. Dolphins are known to dive as deep as 990ft.

Swimming and diving Sperm whales can stay under for at least an hour and are known to dive 7,380 ft The long deep dives require crucial adaptations

Diving They must be able to go long times without breathing. To get as much oxygen before dives, pinnipeds and cetaceans hold their breath for 15 to 30 seconds, then rapidly exhale and take a new breath

Diving Marine mammals are also better at absorbing the oxygen from the air and storing it in their blood. They have relatively more blood than non-diving mammals. Their blood also contains a higher concentration of erythrocytes which contain more hemoglobin. Muscles are very rich in myoglobin, which can store a lot of oxygen

Diving When they dive, the heart rate slows down dramatically. Blood flow to non-essential body parts, like extremities or the intestines, are reduced, but it is concentrated to vital organs like the brain and the heart.

Diving Nitrogen dissolves much better at higher pressures, like those experienced at depths The blood of scuba divers picks up nitrogen while they are below the surface If pressure is suddenly released, some of the nitrogen will not stay dissolved and form tiny bubbles in the blood

Diving When nitrogen bubbles form in the blood after diving, they can lodge in the joints or block the flow of blood to the brain and other organs This produces a horribly painful condition known as the bends or decompression sickness.

Diving When marine mammals dive, their lungs collapse They have a flexible rib cage that gets pushed in by the pressure of the water This squeezes air out of the areas around the lungs Air is moved in the central spaces of the lungs where little nitrogen is absorbed

Behavior Echolocation is just one indication of the mental capabilities of marine mammals Most marine mammals are highly social animals that live in groups at least part of the time. To keep in contact, many of their highly complex and sophisticated behaviors are directed toward members of their own species.

Behavior Sounds, or vocalizations play a large role in communication Cetaceans produce a rich variety of vocalizations that are different from the sounds used for echolocation. Both types of sounds can be produced simultaneously, providing further evidence of the complexity of sound production

Behavior Cetaceans are also well known for their play behavior, pleasurable activities with no serious goal.

Behavior When one individual is in trouble, others may come to assist. Members of a pod refuse to leave a wounded or dying comrade Whalers knew that a harpooned whale was a lure for others. Dolphins will carry injured individuals to the surface to breath, and there are records of females carrying the body of a stillborn calf until it rots.

Behavior One of the mysteries of the behavior of whales and dolphins is the stranding, or beaching, of individuals, sometimes dozens on beaches. The animals refuse to move, and efforts to move them to deeper water usually fail. Even if they are pulled to sea, they usually beach themselves again

Behavior

Stranding whales have been recently linked to high-intensity sonar that uses bursts of intense sound waves. Whales stranded after naval exercises where sonar was used showed hemorrhages in the brain and inner ears, which caused disorientation and death.

Migrations Many pinnipeds and cetaceans make seasonal migrations from feeding grounds to breeding areas.