2. reduced seal and sea lion populations leads killer whales to begin preying on sea otters

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2. Reduced seal and sea lion populations leads killer whales to begin preying on sea otters. 1. Competition with humans for pollock and other prey is one hypothesis that may explain reductions in the 1980s in populations of Stellar sea lions and harbor seals. - PowerPoint PPT Presentation


  • Science/Local: An Aleutian Islands mystery: Why did sea otter populations fall by up to 90% in the 1990s?

    Doroff et al. (2003), Estes et al. (1998), and Kaiser (1998) highlight trophic interactions involving as few as four killer whales. Before 1991, killer whales had never been observed to prey on sea otters. Everything you otter knowabout ENVIR 100 in one 80lb bundle of fur and loveGlobal/Social: The tragedy of the furThe sea otter (Enhydra lutris) has at least three claims to fame other than being adorable: it is the smallest marine mammal (Kenyon 1969), it uses tools (opening shellfish by banging them with rocks or with other shellfish), and it has the densest fur of any animal: approximately 100,000 hairs per square centimeter (Kenyon 1969), compared with perhaps 150 for humans (Jimenez 1999). This fur allows it to survive in the ocean without blubber. It also made sea otter pelts extremely valuable.Sea otters were probably hunted by indigenous human populations for thousands of years (Kenyon 1969) in their original range, shown below. Rapid over-exploitation began in the mid-to-late 1700s, when pelts were taken during the Bering and Cook expeditions and sold in China for prices that exceeded many workers annual salary. Kenyon (1969) estimates that world populations subsequently fell from perhaps 150,000 animals in 1740 to perhaps 1,500 animals by 1900. Prior to their international protection as part of the 1911 Fur Seal Treaty, increasingly rare pelts were selling for as much as $1,125 (Kenyon 1969). By the end of the 19th century the sea otter was extinct commercially and nearly extinct as a species".-- Kenyon (1969)Current and historic distribution of sea otter populations. From Lance et al. (2004).AmchitkaLocal/Ethical: Otters are the bomb!In 1950 "refuge manager Bob Jones encountered military activity of an undisclosed nature. Further inquiry revealed that a classified nuclear experiment was planned... When the Fish and Wildlife Service objected as stewards of the island and the sea otters, they were advised to move some of the animals elsewhere and were given $50,000 to do so. -- USFWS 2007Sea otters in Washington. From Lance et al. (2004).Amchitka Island (labeled on the map below left) was a "stronghold of sea otter recovery" after the international protection treaty of 1911. Its status as part of Aleutian Islands National Wildlife Reserve, however, did not stop the U.S. military from conducting three underground nuclear tests on the islands during the Cold War. (Conducting such tests was thought to be the only way to have an enforceable test ban treaty with the Soviet Union. If true, this poses the obvious ethical question of whether the tests were good.) Two months before the third and final testthe 5 megaton Cannikin shot on November 6, 1971eleven Canadians and one American joined forces to protest the shot by sailing into the area in a boat they named Greenpeace (Kohlhoff 2002), a name that stuck to the international environmental group that grew out of their efforts.Otters from Amchitka Island were transplanted to Washington State in 1969 and 1970 to replace local populations that had been driven to extinction by humans in the 1800s. As shown in the graphic at right, the 29 otters transplanted in 1969 appearto have died out, but the 30 otters transplanted in 1970 transplants have thrived. In 2004 their offspring numbered some 743 individuals (Lance et al. 2004) and have begun creating ethical issues of their own. Prior to the mid-1990s the otters stayed on the west side of the Olympic Peninsula, but in the middle of that decade the otters' range expanded around Cape Flattery to include Neah Bay, where potential conflicts over shellfish with the Makah tribe and other humans are more likely. One public comment on the state recovery plan [Lance et al. 2004] said that "The recovery plan is terrible... It appears to me a sea otter population of 500 between Pillar Point and Destruction Island would be best, with the tribes hunting the surplus when available. This would also save a lot of potential future conflict. Allowing the sea otters to expand will deprive most clams, crabs, etc. from state recreation harvest."


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