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-- M a m m a l s --
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| Q 1. | ||
| Could you give me the name of a book that offers information, with illustrations, on sea mammals? |
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| Q 2. | ||
| Why are porpoises and other marine mammals able to dive to greater depths than a man who is not using scuba? What effect does the pressure have on their bodies? |
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| Q 3. | ||
| Is it true that bats sometimes catch fish in the ocean? |
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| Q 4. | ||
| How do the sea mammals get fresh water to drink? Also, do they urinate? |
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| Q 5. | ||
| What type of sounds do marine mammals make, particularly the bottlenosed dolphin? Also, why do they make these sounds? |
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| Q 6. | ||
| When a human baby is born, it often starts breathing only after it is shocked by physical means such as being struck. How has nature arranged it so that the sea-mammal babies begin breathing on their own as soon as they emerge from their mother’s body? |
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| Q 7. | ||
| What are the deepest and longest recorded dives by a sea mammal, and what species accomplished them? |
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| Q 8. | ||
| How can I become a trainer of dolphins and porpoises? |
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| Q 9. | ||
| If I encounter a stranded marine mammal, what agency should I notify, and what should I do until official help arrives? |
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| Q 10. | ||
| Do marine mammals sleep? |
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| Q 11. | ||
| A ranger at a California state beach warned me not to approach an injured or dying sea lion as it could be rabid. Is rabies a serious problem among wild sea lions? |
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| Q 12. | ||
| While in a boat at night in the British Virgin Islands, I saw bats fishing for minnows in the water around the boat. The bats were silvery in color and had a wingspan of 14 to 18 inches. Do you have any information on this behavior? |
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| Q 13. | ||
| Without drinking fresh water, how do whales, pinnipeds, and other sea mammals produce large amounts of milk for their young? |
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| Q 14. | ||
| How do polar bears and marine mammals obtain fresh water to drink? Also, do penguins drink salt water or fresh water? |
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| Q 15. | ||
| Is it true that dolphins evolved from land mammals? |
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| Q&A 1. | Could you give me the name of a book that offers information, with illustrations, on sea mammals? Vashon, Washington |
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| One interesting book, by Norman and Fraser, is entitled “Giant Fishes, Whales and Dolphins”. It is out of print but is frequently seen in used book stores. The National Geographic Society’s “Book of Mammals” contains general information on some porpoises, whales and manatees, along with some superb illustrations. More recently Hall and Kelson published a large volume on the Mammals of North America. This is a technical compendium and is high-priced. |
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| Q&A 2. | Why are porpoises and other marine mammals able to dive to greater depths than a man who is not using scuba? What effect does the pressure have on their bodies? Pensacola, Florida |
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| Porpoises and other diving marine mammals are better equipped in many physiological ways than is man to dive to considerable depths in the ocean. The blood of these animals has approximately 30 percent higher capacity for oxygen transport and storage than has human blood. They are provided also with increased stores of respiratory pigment in the muscles which may contribute significantly to their oxygen reserve. The respiratory center in the brain regulating breathing movements in all mammals is driven by carbon dioxide in the surrounding blood. In the porpoise and other diving mammals this center is far less sensitive to carbon dioxide in fluids bathing it than in other mammals. Consequently they can tolerate considerably higher concentrations of carbon dioxide. Moreover, all diving animals, whether they be birds, reptiles, or mammals, experience a profound slowing of the heart on diving. In the seal, whose normal surface heart rate may be seventy to eighty times a minute, the heart slows to six and ten beats a minute upon diving. |
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| Q&A 3. | Is it true that bats sometimes catch fish in the ocean? Buenos Aires, Argentina |
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| The fishing bat, Pizonyx vivesi, which occurs along the coasts of California and Mexico, is known to catch fish in its long, powerful, hooked claws as it skims over the surface of the water. Since bats normally drink on the wing by swooping down over the surface of a lake, pond, or stream, this method of fishing is probably not too difficult for them. |
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| Q&A 4. | How do the sea mammals get fresh water to drink? Also, do they urinate? Los Angeles, California |
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| Marine mammals apparently do take in some seawater as they feed. Some species have been shown experimentally to tolerate high salt loads – but how they handle the physiologically is unknown. Also unknown is how much saltwater is actually taken in by animals in the wild. Manatees are known to drink freshwater from hoses in marinas. Naturally, they urinate to rid themselves of the nitrogenous wastes produced by the digestion of their food. The kidneys of all mammals operate to eliminate waste materials with maximum conservation of water and other vital metabolites so that the body fluids remain in balance. |
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| Q&A 5. | What type of sounds do marine mammals make, particularly the bottlenosed dolphin? Also, why do they make these sounds? Naples, Florida |
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| Many marine mammals, such as the bottlenosed dolphin, Tursiops truncates, the killer whales, Orcinus orca, the beluga, Delphinapterus leucas, and the California sea lion, Zalophus californiaus, are known to produce so-called squeaks and chirps. These sounds are varying combinations of clicks – very brief, broadband frequency sounds ranging from a fraction of a millisecond to 25 million seconds long. These clicks may be made slowly and distinctly, or they may be given rapidly and sound, to the human ear, like barks or squeals. These sounds are particularly interesting to man because they are used by the animal in echolocation. By emitting some of these sounds and listening to their echos, the animal can discover the shape and/or distance of an object in the water. This can be of special value to mammals that enter muddy estuaries where vision is restricted. The bottlenosed dolphin has two ranges of clicks. The slower repetition clicks give the animal a general idea of objects, while the faster the repetition clicks give finer details. Many other sounds are produced by marine mammals. These have not been adequately researched by scientists, but they are probably related to the social activities of the animals as well as their survival functions. Further information is given in “The Biology of Marine Mammals” edited by Harald Andersen (Academic Press, New York, 1969) and in “Porpoises and Sonar” by Winthrop Kellogg (Phoenix Books, University of Chicago Press, Chicago, Illinois, 1961). |
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| Q&A 6. | When a human baby is born, it often starts breathing only after it is shocked by physical means such as being struck. How has nature arranged it so that the sea-mammal babies begin breathing on their own as soon as they emerge from their mother’s body? Los Angeles, California |
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| Fortunately, for marine mammals, the young are not born as helpless as are human babies. The only marine mammals that calve in the water are the cetaceans, or whales, dolphins, and porpoises, and the sirenians, or manatees and dugongs. When cetaceans give birth, the young are usually born tail-first, so that the head of the calf remains inside the mother’s body until the last instant in case its body becomes lodged during birth. Head-first, or cephalic, births could easily result in drowning of the young animal in this occurred. When the head finally appears, the baby instinctively surfaces immediately for a breath, sometimes with the help of adult members of the herd. Less is known about sirenians, but tail-first births probably are more common than head-first ones in this group also. In sirenians, however, it is possible that the young need to be supported at the surface by the mother until a proper breathing rhythm can be established. |
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| Q&A 7. | What are the deepest and longest recorded dives by a sea mammal, and what species accomplished them? Kaneohe, Hawaii |
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| It is very difficult to determine how deep marine mammals actually dive, although sperm whales, Physeter catodon, are probably the deepest divers. One sperm whale was reportedly found dead, entangled in a cable which had been set at a depth of 2,200 meters. New evidence suggests sperm whales may dive as deep as 3,000m. It is entirely possible that these whales may dive to even greater depths. Sperm whales are capable of very long dives as well. Whalers have reported that this species is capable of remaining submerged for more than one hour. The bottlenosed whales, Hyperoodon ampullatus and H. planifrons, are also reported to be capable of prolonged dives. The Weddell seal, Leptonychotes weddelli, is probably the deepest diving pinniped (seal, sea lion, or walrus) and can reach depths of at least 457 meters. |
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| Q&A 8. | How can I become a trainer of dolphins and porpoises? Morehead City, North Carolina |
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| Most marine mammal trainers have learned their trade as an apprentice to a trainer at an oceanarium. While there may still be opportunities to train as an apprentice, n alternative is to attend a school that offers instruction in exotic animal training (including marine mammals) such as Moorpark College, 7075 Campus Road, Moorpark, California 93021. This school offers both Certificate and Associate in Science Degree programs in exotic animal training and management. A special organization devoted to furthering knowledge in this field is the International Marine Animal Trainer’s Association (IMATA), 7007 Sea World Drive, Orlando, Florida 32809 (c/o Mr. David G. Butcher, President). One may become an associate member of the IMATA and learn firsthand about conditioning marine mammals as the state of the art progresses. |
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| Q&A 9. | If I encounter a stranded marine mammal, what agency should I notify, and what should I do until official help arrives? Old Lyme, Connecticut |
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| The particular agencies that have jurisdiction over marine mammals vary from state to state. If the state has a Marine Patrol, contact the nearest office of that agency. Otherwise, contact the state Department of Fish and Game, the United States Fish and Wildlife Service, or the National Marine Fisheries Service. When reporting a stranding, try to give an accurate description of the stranded animal and its exact location. Under federal law, with stiff fines for violations, all activities other than those associated with the giving of first aid to a marine mammal are illegal. Before attempting to assist a stricken animal, however, human safety should be carefully considered. Large seals and sea lions may become aggressive, whales due to their immense size may inadvertently be hazardous, and dead or diseased animals can pose health threats. In most cases, individuals can be of greatest assistance to the stranded animal by simply keeping other animals and people from harassing it until the arrival of authorities. Further details, including appropriate first-aid procedures for docile animals, are given in “Stranded Marine Mammals – Some Do’s and Don’ts,” available from the University of Washington, Division of Marine Resources, 3716 Brooklyn Avenue, N.E., Seattle, Washington 98105. This bulletin also notes that unhurt seal or sea lion pups temporarily parked on a beach by their mothers should be left untouched exactly where they are found. |
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| Q&A 10. | Do marine mammals sleep? Sepulveda, California |
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| Marine mammals do indeed sleep, but less deeply and for shorter periods of time than humans. Pinnipeds (seals, sea lions, and walruses) and sea otters are not completely restricted to water and will usually sleep on land. When far from land, they sleep at the water surface. Cetaceans (whales and dolphins) typically sleep in short naps at the surface. Among the species “caught napping” by observers at sea are pilot, gray, fin, right, and sperm whales. Collisions between ships and slumbering whales have also been reported. Since all marine mammals must breathe every few minutes, their sleep is adapted for regular surfacing, and they rarely are completely still while sleeping. Interestingly, the bottlenosed dolphin sleeps with only half of its brain at a time, while the other half remains awake. After an hour or so, these roles are reversed. Most marine mammals do not sleep in regular daily patterns. A number of them have been observed continuously for several days without any noted sleeping behavior. Humpback whales apparently do not sleep at all during their long breeding migrations. |
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| Q&A 11. | A ranger at a California state beach warned me not to approach an injured or dying sea lion as it could be rabid. Is rabies a serious problem among wild sea lions? Long Beach, California |
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| To the best of our knowledge, there are no documented cases of rabies being contracted by a California sea lion (Zalophus californianus). In fact, of all marine mammals, only the ringed seal (Phoca hispida) has been known to carry the rabies virus. Rabies can affect any warm-blooded animal, however, and the possibility of such an occurrence should not be ignored. In addition, research by Dr. Alvin Smith of Oregon State University has shown that many marine organisms, including marine mammals, carry viruses that can be transmitted to terrestrial mammals. One example of such an occurrence is the outbreak of a virus that decimated swine herds throughout the United States in the 1950s. According to Smith, this virus is clinically indistinguishable from one which occurs in California sea lions and probably originated in the marine environment. The primary danger to humans encountering sea lions, however, is most likely the risk of infection from a bite. Sea lions can be extremely aggressive, even when sick or injured. Therefore, no attempts should be made to approach a sea lion, except by appropriate authorities familiar with handling these animals. All seals and sea lions in U.S. waters are protected by federal and, in some cases, state laws. If an individual inadvertently endangers the well-being of one of these animals by misdirected attempts to provide assistance, authorities may impose strict penalties on the violator. |
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| Q&A 12. | While in a boat at night in the British Virgin Islands, I saw bats fishing for minnows in the water around the boat. The bats were silvery in color and had a wingspan of 14 to 18 inches. Do you have any information on this behavior? Albuquerque, New Mexico |
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| Bats from three genera are known to catch and eat fish, according to Walker’s Mammals of the World. These genera and their habitats are Myotis (western Mexico including Baja California), Megaderma (the Indo-Pacific), and Noctilio (Mexico to northern Argentina and southeastern Brazil, including Cuba, Hispaniola, Jamaica, and the Lesser Antilles). The fisherman bat (Noctilio leporinus), which is known in the area you visited, fishes at dusk and during the night by zigzagging over the water surface, chirping and catching small surface-swimming fish with its feet. The fisherman bat is estimated to consume 30 to 40 fish each night. It fishes over the sea, in the surf, and in freshwater. The females are described as gray or dull brown, while the males may have bright orange markings. Larger individuals are 5 inches long, with a forearm length of 3.5 inches. Dr. Roderick A. Suthers and graduate student Karen A. Campbell at Indiana University’s “bat lab” are studying how N. leporinus is able to find its underwater prey. As a bat zeros in on a target, it increases the rate of its sonar pulses from less than 100 to 185 pulses per second. When a fish dips below the water surface, it disappears from the bat’s sonar, somehow the bat predicts where its target will be, and still catches the subsurface fish. How the fisherman bat does this is not yet known. Descriptions of the Indiana University experiments are given in “Echolocation of moving targets by the fish-catching bat, Noctilio leporinus,” Journal of Comparative Physiology A, (1984), 155:75-89, and in “Predictive Tracking of Horizontally Moving Targets by the Fishing Bat, Noctilio leporinus” in the forthcoming Animal Sonar: Processes and Performance (Plenum Press). |
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| Q&A 13. | Without drinking fresh water, how do whales, pinnipeds, and other sea mammals produce large amounts of milk for their young? San Fernando, California |
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| Salt regulation in marine mammals is not completely understood; as in most mammals, the primary organ involved in osmoregulation is the kidney. Marine mammals that consume fish obtain sufficient fresh water from the tissues of the fish. Whales and walruses that feed on invertebrates, which are saltier, have a more complex system. In all marine mammals, the period of lactation is particularly stressful to the mother’s water balance. In Chapter 10 of “Mammals of the Sea: Biology and Medicine,” Sam H. Ridgway reports that the milk of both cetaceans and pinnipeds is very rich (high in fat and low in water content), which minimizes the water loss. The ratio of fat to water in the milk is related to the temperature of the environment; cold-water animals produce the richest milk. |
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| Q&A 14. | How do polar bears and marine mammals obtain fresh water to drink? Also, do penguins drink salt water or fresh water? Sepulveda, California |
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| Polar bears (Ursus maritimus) have access to fresh water in the form of snow, ice, and meltwater. In addition, the water content of their food may satisfy some of their freshwater requirements. River dolphins, manatees, and some seals and sea lions also have regular or sporadic access to fresh water and, on certain occasions, take advantage of it. Whether or not these animals actually need to drink fresh water is not known with certainty. Marine dolphins, porpoises, whales, and most seals and sea lions don’t drink fresh water, but may obtain it from a number of sources. Species that primarily eat fish probably get a significant amount of fresh water from the tissues of their prey. Those feeding on shrimplike krill or squids get little or no fresh water in this manner since marine invertebrates have about the same salt content as saltwater. A second source of fresh water for marine mammals may be metabolic water resulting from metabolic breakdown of food, particularly if the food is rich in fats. Although proteins and carbohydrates don’t yield much fresh water, fat metabolism may produce as much as 1 gram of fresh water per gram of fat. A third source is, oddly enough, seawater. Drinking salt water to get fresh water works only if an animal’s kidneys are capable of producing urine that is saltier than seawater; otherwise, the animal suffers a net loss of fresh water as it attempts to rid its body of the imbibed salt. At least some marine mammals have kidneys that can do this. Penguins also can drink seawater. As in other seabirds, lateral nasal glands excrete a highly concentrated salt solution through the penguin’s nostrils, thus ridding the body of the salt load incurred when seawater is drunk. Researchers are investigating possible ways in which marine mammals might excrete salt. One theory suggests that excess salt deposited within and between epidermal cells that are sloughed regularly. |
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| Q&A 15. | Is it true that dolphins evolved from land mammals? Jacksonville, Florida |
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| All cetaceans, including dolphins, are believed to have evolved from land mammals that returned to the sea during the Paleocene epoch about 70 million years ago. Marine and land mammals still have features in common. For example, many aspects of their internal anatomy, dentition, and cranial structure are comparable. Some cetaceans have vestigial hind limbs. Cetaceans appear to share an ancient ancestor with the ungulates, or hoofed mammals. The first marine mammals appeared in the fossil record approximately 50 million years ago. They were members of the suborder Archaeoceti and were poorly adapted to a totally aquatic existence. Many of their skull features resembled those of terrestrial mammals of the same period. The suborder Archaeoceti is now extinct. Many gaps exist in the fossil record of the cetaceans. One question under debate is whether the two extant cetacean suborders – the Odontoceti (toothed whales) and the Mysticeti (baleen whales) – evolved from the same or different ancestors. |
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Rosenstiel School of Marine & Atmospheric Science Library
University of Miami, FL USA 4600 Rickenbacker Causeway, Miami, Florida 33149 Phone: 305 421 4060 Fax: 305 421 9306 E-mail: libcirc@rsmas.miami.edu |
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