- Email: [email protected]
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Jamieson, D., and Regan, R. (1985). Whales are not cetacean resources. In “Advances in Animal Welfare Science, 1984” (M. W. Fox, and L. Mackley, eds), pp. 101–111. MartinusNijhoff, The Hague. Kellert, S. R. (1996). “The Value of Life: Biological Diversity and Human Society.” Island Press, Washington, DC. Kellert, S. R. (1999). “American Perceptions of Marine Mammals and their Management.” Humane Society of the United States, Washington, DC. Kirkwood, J. K., Bennett, P. M., Jepson, P. D., Kuiken, T., Simpson, V. R., and Baker, J. R. (1997). Entanglement in fishing gear and other causes of death in cetaceans stranded on the coasts of England and Wales. Vet. Rec. 141, 94–98. Lavigne, D. M., Scheffer, V. B., and Kellert, S. R. (1999). The evolution of North American attitudes toward marine mammals. In “Conservation and Management of Marine Mammals” (J. R. Twiss, Jr., and R. R. Reeves, eds), pp. 10–47. Smithsonian Institution Press, Washington, DC. Mackenzie, D. (2006). Glimmer of hope for “doomed” fish. New Scientist 11, 10, November. Marino, L., and Lilienfeld, S. O. (1998). Dolphin-assisted therapy: Flawed data, flawed conclusions. Anthrozoös 11, 194–200. Moccia, R. D., and Duncan, I. J. H. (2004). Investigating fear in domestic rainbow trout, Oncorhynchus mykiss, using an avoidance learning task. Appl. Anim. Behav. Sci. 87, 343–354. Nathanson, D. W. (1998). Reply to Marino and Lilienfeld. Anthrozoös 11, 201–202. Nollman, J. (1999). “The Charged Border: Where Whales and Humans Meet.” Holt, New York. Osinga, N., and ‘t Hart, P. (2006). Fish-hook ingestion in seals (Phoca vitulina and Halichoerus grypus): The scale of the problem and a noninvasive method for removing fish-hooks. Aquat. Mamm. 32, 261–264. Raloff, J. (2006). New estimates of the shark-fin trade. Science News, 4 November. http://www.sciencenews.org/articles/20061104/food.asp Rose, N., and Farinato, R. (1995/1999). “The Case Against Marine Mammals in Captivity.” Humane Society of the United States, Washington, DC. Samuels, A., and Spradlin, T. R. (1995). Quantitative behavioral study of bottlenose dolphins in swim-with-dolphin programs in the United States. Mar. Mamm. Sci. 11, 520–544. Sneddon, L. U. (2003). The evidence for pain in fish: The use of morphine as an analgesic. Appl. Anim. Behav. Sci. 83, 153–162. Verrengia, J. (2003). Nearly 1,000 whales drowning daily in fishing nets. www.eurocbc.org/bycatch
Extinctions, Specific DEBORAH A. DUFFIELD
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xtinction of species has been occurring since the dawn of life on Earth. Sometimes this process is a gradual one, with a few species disappearing over a long period of time. Occasionally, the process appears to be quite rapid and widespread; such mass extinctions often result in the disappearance of many of the flora and fauna on Earth in a relatively short period of time. Such a mass extinction is currently taking place, only this time the cause is not climactic, tectonic, or cosmic, but rather is the result of the activities of one species, Homo sapiens (Domning, 1999). It is well established that many species of animals have disappeared over the last 400 years because of humans, including such well-known examples as the passenger pigeon, dodo, quagga, and great auk. Many other lesser-known species of animals, along with many representatives of the plant
kingdom, have also died out because of human activities. It is thought that a total of 1190 species of plants and animals have gone extinct since 1600 (Smith et al., 1993). When this is combined with the countless number of fungi, protists, and bacteria that have disappeared without notice, it is easy to see why this human decimation of the Earth’s living organisms may easily rank among one of the most major mass extinctions that are a part of our planet’s history. Until recently, the effect of human activities has been primarily felt by those species whose members are relatively large and conspicuous. The great Pleistocene extinctions of mammoths and horses in North America, along with the demise in more recent times of many species of large, flightless birds, are examples of this. Being relatively large, it would be expected that marine mammals would have suffered the same fate as their terrestrial counterparts. The size and remoteness of the habitat of most marine mammals, however, spared them the slaughter and resultant slide toward extinction until more recently. In the last few hundred years, technology gave humans the ability to seek out and kill these animals throughout the vast expanses of the ocean, and many marine mammal species have been brought to the verge of extinction. Lack of profitability from increased costs inherent in trying to find fewer animals, coupled with increased public awareness of and resistance to the destruction, has brought a halt to the exploitation of many of these marine mammals, and in some cases the numbers of certain species are on the rise. This fortunate development came too late for three species of marine mammal: Steller’s sea cow (Hydrodamalis gigas), the Caribbean monk seal (Monachus tropicalis), and the Japanese sea lion (Zalophus japonicus). Most recently the river dolphin of the Yantee River (the baiji, Lipotes vexillifer) has become extinct. In addition, one population has become extinct in recent times, the Atlantic gray whale (Eschrichtius robustus). Direct human destruction was the primary cause of these extinctions, and in all cases the story is one of human ignorance, shortsightedness, and greed.
I. Steller’s Sea Cow In the late autumn of 1741, a Russian exploratory vessel, the Saint Peter, wrecked on a bleak, uninhabited island near the western end of the Aleutian chain (Ford, 1966). This island was completely isolated, save for smaller nearby Copper Island, and was over 200 miles from the nearest Russian settlement on the Kamchatka peninsula. As food supplies were practically non-existent in the winter, it was a joyous occasion when it was discovered that the nearshore waters around the island were inhabited by huge, slow-moving, previously unknown marine mammals. These were Steller’s sea cows, later named after the naturalist accompanying the voyage, Georg Wilhelm Steller. Upon killing, this animal provided large quantities of beeflike meat and almond-tasting oil. Throughout the winter, the crew members of the Saint Peter slaughtered sea cows. When in the summer of 1742, the men who survived the winter reached Kamchatka, they spread the word of the wealth in furs to be had in the Bering Sea and Alaska and of the huge sea cow that would provide food necessary for the required long voyages. From then on, fur traders and hunters would stop at Bering Island and Copper Island to slaughter these animals and stock their vessels with meat and oil. In addition, parties hunting fur-bearing animals would winter on these islands and dine on sea cow meat (Stejneger, 1887). By 1754, the sea cow was gone from Copper Island. With its disappearance 14 years later from Bering Island, Hydrodamalis gigas was extinct (Haley, 1978). What little is known about this species comes from the observations and written accounts of Georg Steller and from bones found
Extinctions, Specific
on Bering and Copper Islands. Members of this species were large, fusiform animals with a relatively small head and a horizontally flatted tail. Individuals grew to about 25 ft in length and probably weighed upward of 4 tons. They had short forelimbs with no digits, a tough hide, and thick layers of fat for insulation. These characteristics permitted the animals to survive in the frigid, storm-tossed waters of the north Pacific, far from the tropical areas inhabited by their nearest living relatives, manatees, and dugongs (Domning, 1978). Like other sirenians, these animals were herbivorous, grazing on the large kelp beds that grew in the shallow waters around the Commander Islands. They had no teeth, but rather two flat, horny chewing plates, one in each jaw, between which the animals mashed kelp. Steller observed that they spent most of their day feeding, head down, with their backs exposed. They lived in shallow, sandy areas, preferring the mouths of running streams with their input of freshwater. They may not have been capable of diving (or if so, only near the surface), a characteristic that would have restricted them to the intertidal area outward to the seaward edge and to the surface of this zone (Reeves et al., 1992). This shallow restricted range, coupled with their slow-moving and docile habits, made Steller’s sea cows easy prey for human hunters, even those with relatively primitive weapons and boats. Grazing animals could be easily approached, harpooned, dragged ashore, and butchered (Stejneger, 1936). Often a wounded animal would escape from its killers and swim out to sea. It has been estimated that only one out of every five sea cows killed was actually utilized for food. Even though this species apparently lived all along the rim of the North Pacific into the late Pleistocene, by the early eighteenth century it was confined as a relict population to the shallow waters around the Commander Islands. This reduction of numbers was thought to be possibly a result of hunting by indigenous peoples (Whitmore, 1977). In 1741, the population was estimated to be no more than 2000 individuals, and relentless hunting pressure, together with the wasteful harvest method, led the complete extermination of Steller’s sea cow by 1768 (Stejneger, 1887). Even though there have been reports of sightings in the North Pacific of animals reputed to be sea cows, some as recently as 1977, it is almost certain that H. gigas was driven to extinction over 200 years ago.
II. Caribbean Monk Seal Nearly 300 years before the Bering expedition and almost half a world away, the demise of another species of marine mammal at the hands of Europeans began. In 1494, on his second voyage to the Caribbean, Columbus discovered the Caribbean monk seal (Monachus tropicalis) on the coast of Santo Domingo (Hispaniola). He ordered his men to kill eight of these “sea wolves” for food, and from that time on the killing never ceased (King, 1983). Probably confined to sandy beaches on remote islands and atolls because of centuries of aboriginal hunting on large islands and the mainland, the monk seals were sought out and ruthlessly slaughtered by fishermen, turtle hunters, buccaneers, and organized sealers. In the Bahamas, up to 100 seals per night were known to be killed (Maxwell, 1967). By the mid-nineteenth century, many zoologists thought that the Caribbean monk seal was already extinct. However, in 1886 a small herd was discovered near the Yucatan peninsula, and because so little was known about the species, North American museums sent expeditions out to gather specimens. One of these expeditions killed 49 seals, 5 of which were pregnant females with near-term fetuses (Ward, 1887). For a species in such precarious circumstances, such activities of science were also of no help. The last confirmed sighting was reported by C. Bernard Lewis, Director of the Institute of Jamaica, who
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said that until 1952 a small colony existed at Seranilla Bank, halfway between Jamaica and Honduras (Rice, 1973). Since that time, although some pinnipeds have been sighted in the Caribbean (these probably being individuals of other seal or sea lion species outside of their normal range), no confirmable sighting of a monk seal in the Caribbean has been made. In 1996, the International Union for the Conservation of Nature declared M. tropicalis extinct. Even though known to Europeans for over 400 years, little scientific information was obtained concerning the Caribbean monk seal before its disappearance. The species belongs to the family Phocidae, and with the Mediterranean monk seal (Monachus monachus) and the Hawaiian monk seal (Monachus schauinslandi) comprise the genus Monachus. The Caribbean species was apparently very similar to the other two monk seals, with males reaching 6–7 ft in length, and females somewhat smaller. The fur of adults was brown on back with a gray tinge and yellowish on the underside. The fur of pups was dark to black. Pupping probably peaked in December, a time different from that of the other two species (Kenyon, 1981). At the time of Columbus, the range of the seal included the shores and islands of the Caribbean Sea and Gulf of Mexico, eastward to the Bahamas and Florida Keys and westward to the Yucatan Peninsula and the Central American coast. The most primitive of all the seals, the three monk seal species probably evolved in areas remote from land predators and never learned to flee nor defend themselves from animals such as humans. In effect, they were “genetically tame” and could easily be clubbed to death by human exploiters (Kenyon, 1981). Like all monk seals, M. tropicalis would have been very sensitive to human disturbance, a fact that usually leads to poor reproduction and pup survival (Bonner, 1990). As humans spread through the Caribbean, these characteristics would ensure that the species declined quickly. It became so scarce by 1887 that it was referred to as an “almost mythical species” (Allen, 1887). Its persecution and demise continued, however, and sometime after 1900 the species went into its inexorable slide to extinction. Although it probably survived until the 1950s, represented mostly by old individuals past reproductive age, the species was doomed due to human slaughter and habitat destruction (Kenyon, 1977). Hoping that the species might somehow have survived in some remote area, extensive surveys were conducted of suitable monk seal habitat in both 1973 and 1984. Sadly, no evidence of the Caribbean monk seal was found, only signs of human habitation and use (LeBoeuf et al., 1986). Although reports of sightings have surfaced into the last decade, the species is almost certainly extinct. As stated by biologist Karl Kenyon (1977): “My conclusion from the 1973 survey is that the Caribbean monk seal has been extinct since the early 1950s. The fact that I saw no monk seals was not as important as the fact of ubiquitous human presence … Even if a few old Caribbean monk seals had survived to the 1970s, all available evidence leads me to believe that there is no hope that the species can recover. Man has now dominated its environment.”
III. Japanese Sea Lion The Japanese sea lion, formerly considered to be a subspecies of the California sea lion, has now been recognized as a separate species, Zalophus japonicus (Rice, 1998). Currently considered extinct by the IUCN, it is possible that a small number of Japanese sea lions may still exist in Korean waters, although the animals reported in Korea may actually be Steller sea lions, Eumetopias jubatus (Nishiwaki, 1973). The Japanese sea lion formerly inhabited the southern sea of Japan and coastal waters of Japan from Hokkaido to Kyushu. No individuals of this species have been seen in Japanese waters for over 50 years.
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Little is known concerning the species, but it is felt to have been morphologically similar to its counterpart, the California sea lion (Zalophus californianus). The Japanese sea lion has probably disappeared due to direct hunting pressure and habitat destruction.
IV. Extinct Population A. Atlantic Gray Whale
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The gray whale (Eschrichtius robustus) is best known as a coastal dwelling cetacean that migrates along the westerncoast of North America from Alaska to Baja California. Almost exterminated by whalers, this population has rebounded as a result of being completely protected, except for aboriginal subsistence hunting (Reilly, 1984). Another population is found in the western North Pacific, where it migrates between the Okhotsk Sea and southern South Korea. This population has been reduced to very low numbers due to overexploitation and is currently highly endangered. A third population in the western North Atlantic appears to have existed until the seventeenth century and was probably rendered extinct by early whaling activity (Mead and Mitchell, 1984). Accounts from this period, although somewhat confusing, describe a whale known as the “scrag” whale, which bears a strong resemblance to the gray whale. Earlier Icelandic accounts describe a “sandloegja,” which is also felt to have been a gray whale (Fraser, 1970). Subfossil remains of gray whales have been found in eastern North America, and radioactive dating has shown the latest to have been from approximately 1675 ad (Mead and Mitchell, 1984). The population went extinct shortly thereafter. Subfossil remains of gray whales have also been found in Europe, but are apparently much older. Therefore, an eastern Atlantic population of gray whales probably also occurred in historical times, apparently going extinct sometime before 500 ad, quite possibly at the hands of early European whalers (van Deinse and Junge, 1937).
V. Prospects for the Future Even though few species of marine mammals have gone extinct at the hands of humans, many have come very close. Elephant seals, fur seals, monk seals, walruses, and sea otters all have narrowly escaped extinction. Among cetaceans, the great rorquals, the gray whale, and the right whales were all nearly exterminated. Some have rebounded, some appear to be slowly increasing; others apparently are not increasing and may never recover. The history of sealing and whaling makes for depressing reading. Although these industries have mostly disappeared in today’s world (with some notable exceptions), some species of marine mammals are still highly endangered. The Mediterranean monk seal is down to less than 1000 individuals and is being forced into tiny pockets of habitat by an explosion of tourism. The vaquita (Phocoena sinus), a small porpoise from the northern Gulf of California, exists as a small population under pressure from unintentional destruction from fisheries (Rojas-Bracho and Taylor, 1999). Many other species are also endangered, although they are not in as precarious a state as these. As much as may be desired, it will never again be possible to observe the “sea wolves” of Columbus lounging on the tropical beaches of the Caribbean or Steller’s sea cow rising out of the northern mists.
See Also the Following Articles California, Galapagos and Japanese Sea Lions ■ Endangered Species and Populations ■ Monk Seals ■ Steller’s Sea Cow
References Allen, J. A. (1887). The West Indian seal (Monachus tropicalis, Gray). Bull. Amer. Mus. Nat. Hist. 2, 1–34. Bonner, W. N. (1990). “The Natural History of Seals.” Facts on File, New York, p. 197. Domning, D. P. (1978). Sirenian evolution in the North Pacific Ocean. In “University of California Publications in Geological Sciences”, Vol. 118. University of California Press, Berkeley, CA, p. 176. Domning, D. P. (1999). Endangered species: The common denominator. In “Conservation and Management of Marine Mammals” (J. R. Twiss, Jr., and R. R. Reeves, eds), pp. 332–341. Smithsonian Institution Press, Washington, DC. Ford, C. (1966). “Where the Sea Breaks Its Back.” Little, Brown, Boston, p. 206. Fraser, F. C. (1970). An early 17th century record of the California gray whale in Icelandic waters. Invest. Cetacea Vol. 2, 13–20. Haley, D. (1978). Steller sea cow. In “Marine Mammals” (D. Haley, ed.), pp. 236–241. Pacific Search Press, Seattle. Kenyon, K. W. (1977). Caribbean monk seal extinct. J. Mammal. 58, 97–98. Kenyon, K. W. (1981). Monk seals. In “Handbook of Marine Mammals” (S. H. Ridgway, and R. J. Harrison, eds), Vol. 2, pp. 195–220. Academic Press, London. King, J. E. (1983). “Seals of the World.” Cornell University Press, Ithaca, NY, p. 240. LeBoeuf, B. J., Kenyon, K. W., and Villa-Ramirez, B. (1986). The Caribbean monk seal is extinct. Mar. Mamm. Sci. 2, 70–72. Maxwell, G. (1967). “Seals of the World.” Constable, London, p. 153. Mead, J. G., and Mitchell, E. D. (1984). Atlantic gray whales. In “The Gray Whale” (M. L. Jones, S. L. Swartz, and S. Leatherwood, eds), pp. 33–53. Academic Press, Orlando, FL. Nishiwaki, M. (1973). Status of the Japanese sea lion. In “Seals,” pp. 80–81. New Series Supplementary Paper No. 39. IUCN, Morges, Switzerland. Reeves, R. R., Stewart, B. S., and Leatherwood, S. (1992). “The Sierra Club Handbook of Seals and Sirenians.” Sierra Club Books, San Francisco, CA, p. 359. Reilly, S. B. (1984). Assessing gray whale abundance: A review. In “The Gray Whale” (M. L. Jones, S. L. Swartz, and S. Leatherwood, eds), pp. 203–223. Academic Press, Orlando, FL. Rice, D. W. (1973). Caribbean monk seal (Monachus tropicalis). In “Seals,” pp. 98–112. New Series Supplementary Paper No. 39. IUCN, Morges, Switzerland. Rice, D. W. (1998). “Marine Mammals of the World: Systematics and Distribution,” Special Publication 4. Society for Marine Mammals, Lawrence, KS, p. 231. Rojas-Bracho, L., and Taylor, B. L. (1999). Risk factors affecting the vaquita (Phocoena sinus). Mar. Mamm. Sci. 15, 974–989. Smith, F. D. M., May, R. M., Pellew, T. H., Johnson, T., and Walter, K. (1993). How much do we know about the current extinction rate? Trends Ecol. Evol. 8, 375–378. Stejneger, L. (1887). How the great northern sea cow (Rytina) became exterminated. Am. Nat. 21, 1047–1054. Stejneger, L. (1936). “Georg Wilhelm Steller, the Pioneer of Alaskan Natural History.” Harvard University Press, Cambridge, MA, p. 623. van Deinse, A. B., and Junge, G. C. A. (1937). Recent and older finds of the California gray whale in the Atlantic. Temminckia 2, 161–188. Ward, H. L. (1887). Notes on the life history of Monachus tropicalis, the West Indian seal. Amer. Nat. 21, 257–264. Whitmore, F. C., Jr., and Gard, L. M., Jr. (1977). “Steller’s Sea Cow (Hydrodamalis gigas) of the Late Pleistocene Age from Amchitka, Aleutian Islands, Alaska.” US Government Printing Office, Washington, DC, p. 20.
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Jamieson, D., and Regan, R. (1985). Whales are not cetacean resources. In “Advances in Animal Welfare Science, 1984” (M. W. Fox, and L. Mackley, eds), pp. 101–111. MartinusNijhoff, The Hague. Kellert, S. R. (1996). “The Value of Life: Biological Diversity and Human Society.” Island Press, Washington, DC. Kellert, S. R. (1999). “American Perceptions of Marine Mammals and their Management.” Humane Society of the United States, Washington, DC. Kirkwood, J. K., Bennett, P. M., Jepson, P. D., Kuiken, T., Simpson, V. R., and Baker, J. R. (1997). Entanglement in fishing gear and other causes of death in cetaceans stranded on the coasts of England and Wales. Vet. Rec. 141, 94–98. Lavigne, D. M., Scheffer, V. B., and Kellert, S. R. (1999). The evolution of North American attitudes toward marine mammals. In “Conservation and Management of Marine Mammals” (J. R. Twiss, Jr., and R. R. Reeves, eds), pp. 10–47. Smithsonian Institution Press, Washington, DC. Mackenzie, D. (2006). Glimmer of hope for “doomed” fish. New Scientist 11, 10, November. Marino, L., and Lilienfeld, S. O. (1998). Dolphin-assisted therapy: Flawed data, flawed conclusions. Anthrozoös 11, 194–200. Moccia, R. D., and Duncan, I. J. H. (2004). Investigating fear in domestic rainbow trout, Oncorhynchus mykiss, using an avoidance learning task. Appl. Anim. Behav. Sci. 87, 343–354. Nathanson, D. W. (1998). Reply to Marino and Lilienfeld. Anthrozoös 11, 201–202. Nollman, J. (1999). “The Charged Border: Where Whales and Humans Meet.” Holt, New York. Osinga, N., and ‘t Hart, P. (2006). Fish-hook ingestion in seals (Phoca vitulina and Halichoerus grypus): The scale of the problem and a noninvasive method for removing fish-hooks. Aquat. Mamm. 32, 261–264. Raloff, J. (2006). New estimates of the shark-fin trade. Science News, 4 November. http://www.sciencenews.org/articles/20061104/food.asp Rose, N., and Farinato, R. (1995/1999). “The Case Against Marine Mammals in Captivity.” Humane Society of the United States, Washington, DC. Samuels, A., and Spradlin, T. R. (1995). Quantitative behavioral study of bottlenose dolphins in swim-with-dolphin programs in the United States. Mar. Mamm. Sci. 11, 520–544. Sneddon, L. U. (2003). The evidence for pain in fish: The use of morphine as an analgesic. Appl. Anim. Behav. Sci. 83, 153–162. Verrengia, J. (2003). Nearly 1,000 whales drowning daily in fishing nets. www.eurocbc.org/bycatch
Extinctions, Specific DEBORAH A. DUFFIELD
E
xtinction of species has been occurring since the dawn of life on Earth. Sometimes this process is a gradual one, with a few species disappearing over a long period of time. Occasionally, the process appears to be quite rapid and widespread; such mass extinctions often result in the disappearance of many of the flora and fauna on Earth in a relatively short period of time. Such a mass extinction is currently taking place, only this time the cause is not climactic, tectonic, or cosmic, but rather is the result of the activities of one species, Homo sapiens (Domning, 1999). It is well established that many species of animals have disappeared over the last 400 years because of humans, including such well-known examples as the passenger pigeon, dodo, quagga, and great auk. Many other lesser-known species of animals, along with many representatives of the plant
kingdom, have also died out because of human activities. It is thought that a total of 1190 species of plants and animals have gone extinct since 1600 (Smith et al., 1993). When this is combined with the countless number of fungi, protists, and bacteria that have disappeared without notice, it is easy to see why this human decimation of the Earth’s living organisms may easily rank among one of the most major mass extinctions that are a part of our planet’s history. Until recently, the effect of human activities has been primarily felt by those species whose members are relatively large and conspicuous. The great Pleistocene extinctions of mammoths and horses in North America, along with the demise in more recent times of many species of large, flightless birds, are examples of this. Being relatively large, it would be expected that marine mammals would have suffered the same fate as their terrestrial counterparts. The size and remoteness of the habitat of most marine mammals, however, spared them the slaughter and resultant slide toward extinction until more recently. In the last few hundred years, technology gave humans the ability to seek out and kill these animals throughout the vast expanses of the ocean, and many marine mammal species have been brought to the verge of extinction. Lack of profitability from increased costs inherent in trying to find fewer animals, coupled with increased public awareness of and resistance to the destruction, has brought a halt to the exploitation of many of these marine mammals, and in some cases the numbers of certain species are on the rise. This fortunate development came too late for three species of marine mammal: Steller’s sea cow (Hydrodamalis gigas), the Caribbean monk seal (Monachus tropicalis), and the Japanese sea lion (Zalophus japonicus). Most recently the river dolphin of the Yantee River (the baiji, Lipotes vexillifer) has become extinct. In addition, one population has become extinct in recent times, the Atlantic gray whale (Eschrichtius robustus). Direct human destruction was the primary cause of these extinctions, and in all cases the story is one of human ignorance, shortsightedness, and greed.
I. Steller’s Sea Cow In the late autumn of 1741, a Russian exploratory vessel, the Saint Peter, wrecked on a bleak, uninhabited island near the western end of the Aleutian chain (Ford, 1966). This island was completely isolated, save for smaller nearby Copper Island, and was over 200 miles from the nearest Russian settlement on the Kamchatka peninsula. As food supplies were practically non-existent in the winter, it was a joyous occasion when it was discovered that the nearshore waters around the island were inhabited by huge, slow-moving, previously unknown marine mammals. These were Steller’s sea cows, later named after the naturalist accompanying the voyage, Georg Wilhelm Steller. Upon killing, this animal provided large quantities of beeflike meat and almond-tasting oil. Throughout the winter, the crew members of the Saint Peter slaughtered sea cows. When in the summer of 1742, the men who survived the winter reached Kamchatka, they spread the word of the wealth in furs to be had in the Bering Sea and Alaska and of the huge sea cow that would provide food necessary for the required long voyages. From then on, fur traders and hunters would stop at Bering Island and Copper Island to slaughter these animals and stock their vessels with meat and oil. In addition, parties hunting fur-bearing animals would winter on these islands and dine on sea cow meat (Stejneger, 1887). By 1754, the sea cow was gone from Copper Island. With its disappearance 14 years later from Bering Island, Hydrodamalis gigas was extinct (Haley, 1978). What little is known about this species comes from the observations and written accounts of Georg Steller and from bones found
Extinctions, Specific
on Bering and Copper Islands. Members of this species were large, fusiform animals with a relatively small head and a horizontally flatted tail. Individuals grew to about 25 ft in length and probably weighed upward of 4 tons. They had short forelimbs with no digits, a tough hide, and thick layers of fat for insulation. These characteristics permitted the animals to survive in the frigid, storm-tossed waters of the north Pacific, far from the tropical areas inhabited by their nearest living relatives, manatees, and dugongs (Domning, 1978). Like other sirenians, these animals were herbivorous, grazing on the large kelp beds that grew in the shallow waters around the Commander Islands. They had no teeth, but rather two flat, horny chewing plates, one in each jaw, between which the animals mashed kelp. Steller observed that they spent most of their day feeding, head down, with their backs exposed. They lived in shallow, sandy areas, preferring the mouths of running streams with their input of freshwater. They may not have been capable of diving (or if so, only near the surface), a characteristic that would have restricted them to the intertidal area outward to the seaward edge and to the surface of this zone (Reeves et al., 1992). This shallow restricted range, coupled with their slow-moving and docile habits, made Steller’s sea cows easy prey for human hunters, even those with relatively primitive weapons and boats. Grazing animals could be easily approached, harpooned, dragged ashore, and butchered (Stejneger, 1936). Often a wounded animal would escape from its killers and swim out to sea. It has been estimated that only one out of every five sea cows killed was actually utilized for food. Even though this species apparently lived all along the rim of the North Pacific into the late Pleistocene, by the early eighteenth century it was confined as a relict population to the shallow waters around the Commander Islands. This reduction of numbers was thought to be possibly a result of hunting by indigenous peoples (Whitmore, 1977). In 1741, the population was estimated to be no more than 2000 individuals, and relentless hunting pressure, together with the wasteful harvest method, led the complete extermination of Steller’s sea cow by 1768 (Stejneger, 1887). Even though there have been reports of sightings in the North Pacific of animals reputed to be sea cows, some as recently as 1977, it is almost certain that H. gigas was driven to extinction over 200 years ago.
II. Caribbean Monk Seal Nearly 300 years before the Bering expedition and almost half a world away, the demise of another species of marine mammal at the hands of Europeans began. In 1494, on his second voyage to the Caribbean, Columbus discovered the Caribbean monk seal (Monachus tropicalis) on the coast of Santo Domingo (Hispaniola). He ordered his men to kill eight of these “sea wolves” for food, and from that time on the killing never ceased (King, 1983). Probably confined to sandy beaches on remote islands and atolls because of centuries of aboriginal hunting on large islands and the mainland, the monk seals were sought out and ruthlessly slaughtered by fishermen, turtle hunters, buccaneers, and organized sealers. In the Bahamas, up to 100 seals per night were known to be killed (Maxwell, 1967). By the mid-nineteenth century, many zoologists thought that the Caribbean monk seal was already extinct. However, in 1886 a small herd was discovered near the Yucatan peninsula, and because so little was known about the species, North American museums sent expeditions out to gather specimens. One of these expeditions killed 49 seals, 5 of which were pregnant females with near-term fetuses (Ward, 1887). For a species in such precarious circumstances, such activities of science were also of no help. The last confirmed sighting was reported by C. Bernard Lewis, Director of the Institute of Jamaica, who
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said that until 1952 a small colony existed at Seranilla Bank, halfway between Jamaica and Honduras (Rice, 1973). Since that time, although some pinnipeds have been sighted in the Caribbean (these probably being individuals of other seal or sea lion species outside of their normal range), no confirmable sighting of a monk seal in the Caribbean has been made. In 1996, the International Union for the Conservation of Nature declared M. tropicalis extinct. Even though known to Europeans for over 400 years, little scientific information was obtained concerning the Caribbean monk seal before its disappearance. The species belongs to the family Phocidae, and with the Mediterranean monk seal (Monachus monachus) and the Hawaiian monk seal (Monachus schauinslandi) comprise the genus Monachus. The Caribbean species was apparently very similar to the other two monk seals, with males reaching 6–7 ft in length, and females somewhat smaller. The fur of adults was brown on back with a gray tinge and yellowish on the underside. The fur of pups was dark to black. Pupping probably peaked in December, a time different from that of the other two species (Kenyon, 1981). At the time of Columbus, the range of the seal included the shores and islands of the Caribbean Sea and Gulf of Mexico, eastward to the Bahamas and Florida Keys and westward to the Yucatan Peninsula and the Central American coast. The most primitive of all the seals, the three monk seal species probably evolved in areas remote from land predators and never learned to flee nor defend themselves from animals such as humans. In effect, they were “genetically tame” and could easily be clubbed to death by human exploiters (Kenyon, 1981). Like all monk seals, M. tropicalis would have been very sensitive to human disturbance, a fact that usually leads to poor reproduction and pup survival (Bonner, 1990). As humans spread through the Caribbean, these characteristics would ensure that the species declined quickly. It became so scarce by 1887 that it was referred to as an “almost mythical species” (Allen, 1887). Its persecution and demise continued, however, and sometime after 1900 the species went into its inexorable slide to extinction. Although it probably survived until the 1950s, represented mostly by old individuals past reproductive age, the species was doomed due to human slaughter and habitat destruction (Kenyon, 1977). Hoping that the species might somehow have survived in some remote area, extensive surveys were conducted of suitable monk seal habitat in both 1973 and 1984. Sadly, no evidence of the Caribbean monk seal was found, only signs of human habitation and use (LeBoeuf et al., 1986). Although reports of sightings have surfaced into the last decade, the species is almost certainly extinct. As stated by biologist Karl Kenyon (1977): “My conclusion from the 1973 survey is that the Caribbean monk seal has been extinct since the early 1950s. The fact that I saw no monk seals was not as important as the fact of ubiquitous human presence … Even if a few old Caribbean monk seals had survived to the 1970s, all available evidence leads me to believe that there is no hope that the species can recover. Man has now dominated its environment.”
III. Japanese Sea Lion The Japanese sea lion, formerly considered to be a subspecies of the California sea lion, has now been recognized as a separate species, Zalophus japonicus (Rice, 1998). Currently considered extinct by the IUCN, it is possible that a small number of Japanese sea lions may still exist in Korean waters, although the animals reported in Korea may actually be Steller sea lions, Eumetopias jubatus (Nishiwaki, 1973). The Japanese sea lion formerly inhabited the southern sea of Japan and coastal waters of Japan from Hokkaido to Kyushu. No individuals of this species have been seen in Japanese waters for over 50 years.
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Little is known concerning the species, but it is felt to have been morphologically similar to its counterpart, the California sea lion (Zalophus californianus). The Japanese sea lion has probably disappeared due to direct hunting pressure and habitat destruction.
IV. Extinct Population A. Atlantic Gray Whale
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The gray whale (Eschrichtius robustus) is best known as a coastal dwelling cetacean that migrates along the westerncoast of North America from Alaska to Baja California. Almost exterminated by whalers, this population has rebounded as a result of being completely protected, except for aboriginal subsistence hunting (Reilly, 1984). Another population is found in the western North Pacific, where it migrates between the Okhotsk Sea and southern South Korea. This population has been reduced to very low numbers due to overexploitation and is currently highly endangered. A third population in the western North Atlantic appears to have existed until the seventeenth century and was probably rendered extinct by early whaling activity (Mead and Mitchell, 1984). Accounts from this period, although somewhat confusing, describe a whale known as the “scrag” whale, which bears a strong resemblance to the gray whale. Earlier Icelandic accounts describe a “sandloegja,” which is also felt to have been a gray whale (Fraser, 1970). Subfossil remains of gray whales have been found in eastern North America, and radioactive dating has shown the latest to have been from approximately 1675 ad (Mead and Mitchell, 1984). The population went extinct shortly thereafter. Subfossil remains of gray whales have also been found in Europe, but are apparently much older. Therefore, an eastern Atlantic population of gray whales probably also occurred in historical times, apparently going extinct sometime before 500 ad, quite possibly at the hands of early European whalers (van Deinse and Junge, 1937).
V. Prospects for the Future Even though few species of marine mammals have gone extinct at the hands of humans, many have come very close. Elephant seals, fur seals, monk seals, walruses, and sea otters all have narrowly escaped extinction. Among cetaceans, the great rorquals, the gray whale, and the right whales were all nearly exterminated. Some have rebounded, some appear to be slowly increasing; others apparently are not increasing and may never recover. The history of sealing and whaling makes for depressing reading. Although these industries have mostly disappeared in today’s world (with some notable exceptions), some species of marine mammals are still highly endangered. The Mediterranean monk seal is down to less than 1000 individuals and is being forced into tiny pockets of habitat by an explosion of tourism. The vaquita (Phocoena sinus), a small porpoise from the northern Gulf of California, exists as a small population under pressure from unintentional destruction from fisheries (Rojas-Bracho and Taylor, 1999). Many other species are also endangered, although they are not in as precarious a state as these. As much as may be desired, it will never again be possible to observe the “sea wolves” of Columbus lounging on the tropical beaches of the Caribbean or Steller’s sea cow rising out of the northern mists.
See Also the Following Articles California, Galapagos and Japanese Sea Lions ■ Endangered Species and Populations ■ Monk Seals ■ Steller’s Sea Cow
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