On his 1990s cruises to the Aleutians, he and other biologists noticed a 25 percent decline in sea otters each year. By Environmental News Network staff. Orcas were eating otters because the really big whales they used to eat were nearly wiped out by commercial whalers back in the 1950s. It explains that the possible eradication of the kelp forests will pose a great threat to the ecological balance and the fishing industry of the region. Yet, individual ecotypes or populations are often extremely specialized. What effects do you expect sea otters to have on the rest of the kelp forest community. 1) 1st killer whale attack on sea otter observed. As a result, the population of sea urchins has risen dramatically, and the sea urchins began eating kelp at an alarming rate. The number of sea otters in Clam Lagoon remained stable from 1993 to 1997, while sea otters in nearby Kuluk Bay disappeared at a rate five times greater. This, of course, begs the very important question: Killer whales and sea otters had co-existed peacefully for decades prior to the 1990s, so why would the whales suddenly start eating otters? ©2020 Geophysical Institute, University of Alaska Fairbanks. Please report any problems or feedback concerning this website to uaf-rcs@alaska.edu. John Dornellas, 37, filmed sea otter frantically swim towards his boat for safety 2) Contrasted decline in 2 aras. Try our expert-verified textbook solutions with step-by-step explanations. Sea otters are getting harder to find along the western part of the Aleutian chain. What do you think has caused the killer whales to start eating sea otters? One killer whale with a taste for sea otters could eat more than 1,800 sea otters a year, Estes said. Sea otter being chased by a killer whale leaps to safety on a boat with just seconds to spare. Hatfield concluded that the lack of reports of killer whales eating sea otters may be due to the fact that killer whales have only recently shifted their diets to include sea otters, possibly because of the decline of Steller sea lions and harbor seals. Some biologists think the missing otters of western Alaska have disappeared to an unlikely place--the bellies of killer whales. Icon Attribution: Newspaper by Alexandria Eddings from the Noun Project, Killer Whales Develop a Taste For Sea Otters, The northern shrike: songbird like no other. In support of this theory, the first well-documented attack of a sea otter by a transient killer whale was observed in 1991, with 9 other attacks observed since then. Their favorite prey has always been sea lions and seals. Alaska Science Forum article has no image, a placeholder has taken its place. Scientists say killer whales off Alaska have begun hunting sea otters because their usual prey, seals and sea lions, have gone into serious decline. clude that the sea otter population declines were caused by increased mortality. Clam Lagoon is an area uniquely protected from killer whales by a narrow channel only three or four feet deep, while Kuluk Bay is open coastline that offers otters no protection from killer whales. Terms. Estes said he wasn't convinced killer whales were eating sea otters until he and Tim Tinker, also from Santa Cruz, did a study in which they compared two populations of sea otters at Adak Island. 7. The Sea Otter (Enhydra lutris) is the smallest marine mammal in North America – males measure 1.2 metres in length and weigh an average of 45 kilograms (females are a bit smaller).At the same time, the Sea Otter is the largest member of its family, the mustelids, which includes River Otters, weasels, badgers, wolverines and martens. Killer whales are the largest predator of warm-blooded animals alive today.Globally, killer whales appear to have an extremely diverse diet. It was SeaWorld’s first show that did not include trainers in the water with the killer whales. She wails after her baby is eaten by the huge predator. The University of Alaska Fairbanks is an AA/EO employer and educational institution and prohibits illegal discrimination against any individual: Learn more about UA's notice of nondiscrimination. But hungry killer whales aren’t finding enough of their preferred prey: seals and sea lions. The otter is much smaller than the sea lions and seals so the killer whales must eat … Comparison of the weight and metabolic rate of sea otters and killer whales suggests that only 2-4 whales could eat 40000 sea otters in 6 six years, and due to the fact that the whales move in groups of 25-100, it is possible for them to cause 90% of the reduction. Deprived of their normal food, killer whales turned to the sea otter. Estes said he wasn't convinced killer whales were eating sea otters until he and Tim Tinker, also from Santa Cruz, did a study in which they compared two populations of sea otters at Adak Island. A female killer whale would need to eat 3 (3.1) male sea otters or 5 (4.6) females per day. First, although killer whales and sea otters have been observed in close proximity for decades, the first attack on a sea otter was seen in 1991. "All of the available data point to increased numbers of killer whales as the direct cause of the sea otter decline in southwest Alaska," says coauthor Jim Estes of the U.S.G.S. Let's get otter here! The number of sea otters in Clam Lagoon remained stable from 1993 to 1997, while sea otters in nearby Kuluk Bay disappeared at a rate five times greater. The Orca diet also consists fish, squid, seals, sea lions, dolphins, porpoises, and large whales such as the Blue Whale. A male killer whale would need to eat 5 (4.66) male sea otters or 7 (6.9) females per day. Course Hero is not sponsored or endorsed by any college or university. Kuluk Bay had a rapidly decreasing sea otter number which Clam Lagoons fluctuates normally. Humans also kill sea otters when they use fishing gear that traps the otter or hit the otter with boats. "All of us commented on how peculiar that was.". Sea otter being chased by a killer whale leaps to safety on a boat with just seconds to spare. One method the whales used was to breach near floating otters and land on top of them, presumably eating the stunned otters underwater because the animals never returned to the surface. These small urchins also readily devour kelp, and if their numbers swell, they begin to thin out kelp forests. Hatfield concluded that the lack of reports of killer whales eating sea otters may be due to the fact that killer whales have only recently shifted their diets to include sea otters, possibly because of the decline of Steller sea lions and harbor seals. However, it is true that the cost to clean and rehabilitate oiled sea otters was about $80,000 per animal. What is kelp and why is it important? October 19, 1998 Web posted at: 2:50 PM EDT. Estes and his colleagues estimate that a single killer whale will have to eat 1,825 otters a year to get its required nourishment. Killer whales have a diverse diet, although individual populations often specialize in particular types of prey. And they sometimes use rocks to break open their prey. As a result, populations of sea otters in the Aleutian Islands have declined from an estimated 60,000 animals in the mid-1980s to under 10,000 by 2000. California, gathered anecdotes for a study to determine why killer whales whales to. 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