Appendix B
An Introduction to Marine Mammals

Three orders of the class Mammalia contain marine mammals: Cetacea, Carnivora, and Sirenia. (There is a section on each of the three orders in this appendix. Each includes a table listing the marine mammals in that order.) The size range of marine mammals is immense, varying from a newborn sea otter weighing perhaps 1 kilogram (kg) to the largest female blue whale weighing about 100,000 kg. Their habitats are also quite varied, encompassing all seas and numerous coastal areas and shores as well as some freshwater lakes and rivers.

All extant Cetacea and Sirenia normally spend their entire lives in water. In contrast, marine mammals of the order Carnivora are semiaquatic, often hauling out on land. Some of these semiaquatic mammals spend considerable periods of time (many months) in the water, often hundreds or even thousands of kilometers at sea away from haul-out or breeding areas. Families of marine mammals of the order Carnivora are these: Otariidae, or eared seals (fur seals and sea lions); Odobenidae (walrus); Phocidae (true seals); Mustelidae (chungungo and sea otter); and Ursidae (polar bear).

In the United States, all marine mammals are legally protected by the Marine Mammal Protection Act of 1972 (MMPA). The species of the order Cetacea and suborder Pinnipedia that live strictly in freshwater are also protected under this law, and thus they are included in this discussion. Under the 1972 act, the U.S. Fish and Wildlife Service (FWS) of the U.S. Department of the Interior is responsible



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 65
--> Appendix B An Introduction to Marine Mammals Three orders of the class Mammalia contain marine mammals: Cetacea, Carnivora, and Sirenia. (There is a section on each of the three orders in this appendix. Each includes a table listing the marine mammals in that order.) The size range of marine mammals is immense, varying from a newborn sea otter weighing perhaps 1 kilogram (kg) to the largest female blue whale weighing about 100,000 kg. Their habitats are also quite varied, encompassing all seas and numerous coastal areas and shores as well as some freshwater lakes and rivers. All extant Cetacea and Sirenia normally spend their entire lives in water. In contrast, marine mammals of the order Carnivora are semiaquatic, often hauling out on land. Some of these semiaquatic mammals spend considerable periods of time (many months) in the water, often hundreds or even thousands of kilometers at sea away from haul-out or breeding areas. Families of marine mammals of the order Carnivora are these: Otariidae, or eared seals (fur seals and sea lions); Odobenidae (walrus); Phocidae (true seals); Mustelidae (chungungo and sea otter); and Ursidae (polar bear). In the United States, all marine mammals are legally protected by the Marine Mammal Protection Act of 1972 (MMPA). The species of the order Cetacea and suborder Pinnipedia that live strictly in freshwater are also protected under this law, and thus they are included in this discussion. Under the 1972 act, the U.S. Fish and Wildlife Service (FWS) of the U.S. Department of the Interior is responsible

OCR for page 65
--> for administering regulations concerning polar bears, walrus, sirenians, and sea otters; the National Marine Fisheries Service of the U.S. Department of Commerce is responsible for whales, dolphins, seals, sea lions, and other marine mammals not regulated by FWS. In addition, another independent body established under the MMPA, the Marine Mammal Commission, maintains a scientific committee to advise on issues related to marine mammal conservation. Those species designated as endangered are further protected under the Endangered Species Act of 1973. Threats to marine mammal populations worldwide are many. They result, for example, from fishing (the use of gillnets, driftnets, ghost nets, long lines, the yellowfin tuna purse seine, rolling hooks), pollution (agricultural runoff, industrial waste, petroleum spills, trash dumping), deforestation and development of the rain forests, damming, oil field development, mining, heavy-vessel traffic, and other human activities. Twenty species of marine mammals are listed as endangered under U.S. provisions (see the tables in this appendix), although some of them appear to be gaining in population and may be removed from endangered status (Brownell et al., 1989). For example, the eastern or California stock of the gray whale Eschrichtius robustus has apparently recovered from severe exploitation and thus was proposed for removal from the endangered species list by the U.S. Department of Commerce as of 7 January 1993 (Marine Mammal Commission, 1992). Some other marine mammals, such as the Gulf of California porpoise (vaquita) and the Yangtze River dolphin (baiji), appear to be headed for extinction. However, the majority of species are not endangered or seriously threatened. Cetacea: Whales, Dolphins, Porpoises The larger cetaceans include Physeteridae (sperm whales), Ziphoidea (beaked whales and bottlenose whales), and suborder Mysticeti (baleen whales) (Table B-1). Eight of the largest species are listed as endangered. The sperm whale has been on the U.S. List of Endangered and Threatened Wildlife, even though there may be more than a million sperm whales in the world's oceans. Some specific populations are apparently depleted even though the world population is relatively large. Because of their past exploitation by whalers and recent publicity about this exploitation, most large baleen whales are assumed by the public to be endangered species. However, in the absence of the

OCR for page 65
--> TABLE B-1 Classification of Living Mammals of the Order Cetacea Suborder, family, genus, species Common name I. Suborder Odontoceti   Superfamily Platanistoidea   Family Platanistidae   Platanista gangetica Ganges River dolphin, Ganges susu Platanista minor * Indus River dolphin, Indus susu Family Pontoporiidae   Subfamily Lipotinae   Lipotes vexillifer * ** baiji, Yangtze, or Chinese River dolphin Subfamily Pontoporiinae   Pontoporia blainvillei franciscana, cachimbo, La Plata dolphin Family Iniidae   Inia geoffrensis ** boto, boutu, bufeo, Amazon River dolphin Superfamily Delphinoidea   Family Monodontidae   Subfamily Orcaellinae   Orcaella brevirostris Irrawaddy dolphin, pesut Subfamily Delphinapterinae   Delphinapterus leucas ** white whale, beluga Subfamily Monodontinae   Monodon monoceros narwhal   Family Phocoenidae   Subfamily Phocoeninae   Phocoena phocoena ** harbor porpoise Phocoena spinipinnis Burmeister's porpoise Phocoena sinus * vaquita, Gulf of California harbor porpoise Neophocaena phocaenoides finless porpoise Subfamily Phocoenoidinae   Australophocaena dioptrica spectacled porpoise Phocoenoides dalli Dall's porpoise Family Delphinidae   Subfamily Steninae   Steno bredanensis rough-toothed dolphin Sousa chinensis Indopacific hump-backed dolphin Sousa plumbea plumbeous dolphin Sousa teuszii Atlantic hump-backed dolphin Sotalia fluviatilis tucuxi Subfamily Delphininae   Lagenorhynchus albirostris white-beaked dolphin Lagenorhynchus acutus Atlantic white-sided dolphin Lagenorhynchus obscurus dusky dolphin Lagenorhynchus obliquidens Pacific white-sided dolphin Lagenorhynchus cruciger hourglass dolphin Lagenorhynchus australis Peale's dolphin

OCR for page 65
--> Suborder, family, genus, species Common name Grampus griseus Risso's dolphin Tursiops truncatus bottlenose dolphin Stenella frontalis Atlantic spotted dolphin Stenella attenuata pantropical spotted dolphin Stenella longirostris spinner dolphin Stenella clymene clymene dolphin Stenella coeruleoalba striped dolphin Delphinus delphis common dolphin Lagenodelphis hosei Fraser's dolphin Subfamily Lissodelphinae   Lissodelphis borealis northern right whale dolphin Lissodelphis peronii southern right whale dolphin Subfamily Cephalorhynchinae   Cephalorhynchus commersonii Commerson's dolphin Cephalorhynchus eutropia black dolphin, Chilean dolphin Cephalorhynchus heavisidii Heaviside's dolphin Cephalorhynchus hectori Hector's dolphin Subfamily Globicephalinae   Peponocephala electra melon-headed whale, electra dolphin Feresa attenuata pygmy killer whale Pseudorca crassidens ** false killer whale Orcinus orca ** killer whale Globicephala melas long-finned pilot whale Globicephala macrorhynchus short-finned pilot whale Superfamily Ziphoidea.   Family Ziphiidae   Tasmacetus shepherdi Shepherd's beaked whale Berardius bairdii Baird's beaked whale Berardius arnuxii Arnoux's beaked whale Mesoplodon pacificus Longman's beaked whale Mesoplodon bidens Sowerby's beaked whale Mesoplodon densirostris Blainville's beaked whale Mesoplodon europaeus Gervais' beaked whale Mesoplodon layardii strap-toothed whale Mesoplodon hectori Hector's beaked whale Mesoplodon grayi Gray's beaked whale Mesoplodon stejnegeri Stejneger's beaked whale Mesoplodon bowdoini Andrew's beaked whale Mesoplodon mirus True's beaked whale Mesoplodon ginkgodens ginkgo-toothed beaked whale Mesoplodon carlhubbsi Hubb's beaked whale Ziphius cavirostris Cuvier's beaked whale Hyperoodon ampullatus northern bottlenose whale Hyperoodon planifrons southern bottlenose whale

OCR for page 65
--> Suborder, family, genus, species Common name Superfamily Physeteroidea   Family Physeteridae   Subfamily Physeterinae   Physeter macrocephalus * sperm whale Family Kogiidae   Kogia breviceps pygmy sperm whale Kogia simus dwarf sperm whale II. Suborder Mysticeti   Family Balaenidae   Balaena mysticetus * bowhead whale Eubalaena austalis * southern right whale Eubalaena glacialis * northern right whale Family Neobalaenidae   Caperea marginata pygmy right whale Family Eschrichtfiidae   Eschrichtius robustus *1 gray whale Family Balaenopteridae   Subfamily Balaenopterinae   Balaenoptera acutorostrata minke whale Balaenoptera borealis * sei whale Balaenoptera edeni Bryde's whale Balaenoptera musculus * blue whale Balaenoptera physalus * fin whale, finback Subfamily Megapterinae   Megaptera novaeangliae * humpback whale NOTE: * = endangered species; ** = species for which some audiometric information has been published. 1The California stock of gray whales has been recommended for delisting by NMFS. resumption of full commercial whaling, most of these larger cetaceans, including some species of baleen whales that appear on the Endangered Species List are, as species, in reality not endangered. Some of these species have been completely protected for many years, and all are currently protected by the moratorium on commercial whaling promulgated by the International Whaling Commission. As with the sperm whales, however, some populations of large baleen whales remain depleted. Brownell et al. (1989) suggest that some of these large whales be removed from the Endangered Species List and that some small cetaceans be added. With the possible exception of the northern right whale, none of the large cetacean species is currently in peril of extinction (Perrin, 1988). There are more than 40 species of smaller cetaceans, dolphins

OCR for page 65
--> and porpoises, found worldwide. While no cetacean species has been driven to extinction by human endeavors (Perrin, 1988), four species of the smaller cetaceans are in jeopardy in the coming decades if certain human activities in their habitats are not changed (Brownell, 1991; Norris, 1992). These include the baiji, Lipotes vexillifer; the Chilean dolphin, Cephalorhynchus eutropia; the Indus River dolphin, Platanista minor; and the vaquita, Phocoena sinus, of the Gulf of California. The Carnivora: Pinnipeds, Sea Otters, Polar Bears The marine Carnivora all spend some time on land or sea ice to breed and bear their young. The breeding areas are therefore especially sensitive to human encroachment. A few species live in freshwater. Marine mammals in the order Carnivora include fur seals and sea lions, true seals, walrus, chungungo and sea otters, and polar bears (Table B-2). Pinnipedia Pinniped means ''feather footed,'' and the suborder Pinnipedia includes three families: Otariidae (fur seals and sea lions), Odobenidae (walrus), and Phocidae (true seals). Historically, almost all pinnipeds were hunted for fur, meat, oil, or ivory. Brownell (1991) suggests that, although most pinniped species will probably experience an increase in number during the 1990s, at least three species—northern fur seal, Callorhinus ursinus; Steller sea lion, Eumetopias jubatus; and Mediterranean monk seal, Monachus monachus—will continue to decline in the absence of stronger corrective measures. One pinniped species, the Caribbean monk seal, Monachus tropicalis, has apparently become extinct during this century (Kenyon, 1977). Sea Otters The sea otter of the North Pacific, Enhydra lutris, is a coastal animal that is often associated with kelp beds just off the coasts of California, British Columbia, and Alaska. The marine otter off the coasts of Peru and Chile, chungungo, Lutra felina, is severely endangered because the animals are hunted for their prized pelts on the Chilean coast and because Peruvians often shoot them as a menace to fishing (Miller and Rottmann, 1983). Another large otter, Lutra longicaudis of northeast Brazil, is threatened by fishing, clandestine hunting, and habitat degradation (Almeida et al., 1991).

OCR for page 65
--> TABLE B-2 Marine Mammals (Pinnipeds, Otters, Polar Bears) of the Order Carnivora Family, genus, species Common name Family Otariidae of suborder Pinnipedia   Eumetopias jubatus Steller sea lion, northern sea lion Zalophus californianus ** California sea lion Otaria flavescens South American sea lion Neophoca cinerea Australian sea lion Phocartos hookeri New Zealand sea lion Callorhinus ursinus ** northern fur seal Arctocephalus townsendi * Guadalupe fur seal Arctocephalus philippii * Juan Fernández fur seal Arctocephalus galapagoensis Galápalgos fur seal Arctocephalus australis South American fur seal Arctocephalus pusillus Cape fur seal, South African fur seal, Tasmanian fur seal, Victorian fur seal Arctocephalus forsteri New Zealand fur seal, West Australian fur seal Arctocephalus gazella Kerguelen fur seal, Antarctic fur seal Arctocephalus tropicalis Amsterdam Island fur seal Family Odobenidae of suborder   Pinnipedia   Odobenus rosmarus walrus Family Phocidae of suborder   Pinnipedia   Phoca vitulina ** harbor seal Phoca largha larga seal, spotted seal Phoca hispida ** ringed seal Phoca sibirica Caspian seal Phoca groenlandica ** harp seal, Greenland seal Phoca fasciata ribbon seal Erignathus barbatus bearded seal Cystophora cristata hooded seal, bladdernose seal Halichoerus grypus ** gray seal Monachus monachus * Mediterranean monk seal Monachus tropicalis *** West Indian monk seal, Caribbean monk seal Monachus schauinslandi * ** Hawaiian monk seal Mirounga leonina southern elephant seal Mirounga angustirostris northern elephant seal Lobodon carcinophagus crabeater seal Ommatophoca rossii Ross seal Hydrurga leptonyx leopard seal Leptonychotes weddelli Weddell seal Family Mustelidae   Lutra felina * Chungungo, marine otter, gato marino Enhydra lutris sea otter Family Ursidae   Ursus maritimus polar bear NOTES: The otters and bear listed in this table are regarded as marine mammals. Of course, most bears and otters are carnivores but not marine mammals. * = endangered species; ** = species for which some audiometric data are available; *** = extinct species.

OCR for page 65
--> Polar Bears Polar bears from the family Ursidae may be seen in the water some distance at sea. However, they spend most of the year on sea ice or, in the absence of ice, on land. They prey primarily on ringed seals (Phoca hispida). Polar bears also kill other marine mammals such as bearded seals (Erignathus barbatus), white whales (Delphinapterus leucas), and the narwhal (Monodon monoceros). Ringed seal populations are large, but white whales and narwhals, although not endangered,1 are much less numerous. The Sirenia: Manatees and Dugongs (Sea Cows) Although they receive much less attention by the media, the Sirenia are probably more endangered than any of the great whales with the possible exception of right whales. In fact, a sirenian species has become extinct in modern times (in the 1800s)—the great northern sea cow, or Steller's sea cow, Hydrodamalis gigas, of the Bering Sea (Nishiwaki and Marsh, 1985). Dugongs and manatees are the two living genera of Sirenia (Table B-3). They represent two distinct families of plant-grazing marine mammals that are found in separate parts of the world. Dugongs occur in tropical and subtropical shallows of the Indo-Pacific region—northern Australia, the Guangxi coast of China, Indonesia, the Aru Islands, Sri Lanka, India, the Persian Gulf, the Arabian Peninsula, the East African coast, and Madagascar. Other than the dugong, the elephant and the hyrax are the closest living relatives of the manatee. There are three living species of TABLE B-3 Living and Recent Members of the Totally Aquatic Order Sirenia (Sea Cows) Family, genus, species Common name Order Sirenia (sea cows)   Family Dugongidae   Dugong dugon * dugong Hydrodamalis gigas *** Steller's sea cow Family Trichechidae   Trichechus manatus * ** Caribbean manatee Trichechus inunguis * Amazonian manatee Trichechus senegalensis West African manatee NOTES: * = endangered species; ** = some auditory information is available; *** = extinct species.

OCR for page 65
--> manatees: the West Indian or Florida manatee, Trichechus manatus; the West African manatee, T. senegalensis; and the Amazonian manatee, T. inunguis. Manatees prefer shallow estuaries and swampy areas where aquatic plants are abundant (Caldwell and Caldwell, 1985). They are at times found in freshwater, brackish water, or marine waters. West Indian or Caribbean manatees range from Georgia on the coast of the southern United States to the coast of Brazil; however, there is a very patchy distribution over this wide range. The Amazonian manatee is found in the Amazon basin and possibly in parts of the Orinoco River system. The West African manatee is apparently most abundant in the Niger River and its tributaries (Nishiwaki et al., 1982), although there are areas of dense manatee population along the coast of Sierra Leone. References Almeida, R.T., G.P. Pimentel, and F.J.L. Silva. 1991. Occurrence of Otter Lutra longicaudis (Mammalia-Mustelidae) in mangrove area, Pernambuco State—NE Brazil. Abstract from: Ninth Biennial Conference on the Biology of Marine Mammals, Chicago Zoological Society, Chicago. p. 1. Brownell, R.L., Jr. 1991. Marine Mammal Populations in the 1990's: Status, Problems and Research. IBI Reports. 2:1–10. (International Marine Biological Research Institute, Kamogawa, Japan.) Brownell, R.L., Jr., K. Ralls, and W.F. Perrin. 1989. The plight of the 'forgotten' whales. Oceanus 32(1):5–11. Caldwell, D.K., and M.C. Caldwell. 1985. Manatees, Trichechus manatus Linnaeus, 1758; Trichechus senegalensis Link, 1795 and Trichechus inunguis (Natterer, 1883). In: S.H. Ridgway and R.J. Harrison (eds.), Handbook of Marine Mammals, vol. 3. The Sirenians and Baleen Whales. Academic Press, London. pp. 33–66. Kenyon, K.W. 1977. Caribbean monk seal extinct. J. Mammal. 58:97–98. Marine Mammal Commission. 1992. Annual Report of the Marine Mammal Commission: Calendar Year 1991. A report to Congress. U.S. Marine Mammal Commission, Washington, DC. Miller, S.D., and J. Rottmann. 1983. Endangered mammals of Chile: Status and conservation. Biol. Conserv. 25:335–352. Nishiwaki, M., and H. Marsh. 1985. Dugong, Dugong dugon (Muller, 1776). In: S.H. Ridgway and R.J. Harrison (eds.), Handbook of Marine Mammals, vol. 3. The Sirenians and Baleen Whales. Academic Press, London. pp. 1–31. Nishiwaki, M., M. Yamaguchi, S. Shikota, S. Uchida, and T. Kataoka. 1982. Recent survey on the distribution of African manatee. Sci. Rep. Whales Res. Inst. 34:137–147. Norris, K. 1992. Dolphins in Crisis. Nat. Geog. 182(3):2–35. Perrin, W. F. 1988. Dolphins, Porpoises, and Whales: An Action Plan for the Conservation of Biological Diversity: 1988–1992. IUCN, Gland, Switzerland.