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Estes and his colleagues estimate that a single killer whale will have to eat 1,825 otters a year to get its required nourishment. Kuluk Bay had a rapidly decreasing sea otter number which Clam Lagoons fluctuates normally. Why the killer whales changed their diet is still a matter of speculation, but people may be the culprits. Why do orcas eat sea otters? More about affected. 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. What do you think has caused the killer whales to start eating sea otters? A mother otter clambers onto a motorboat in Tutka Bay, Alaska as the white underside of a killer whale chases after her. Although from the Estes and his group study, it is clear that the killer whales have been the cause of the decline in the population of sea otters in Alaska, this has been greatly contributed to the fight for the survival of the whales and also the ecological interaction of the animals and their … However, these two have experienced a significant decline in their population. The killer whale, also known as an orca (Orcinus orca), is a toothed whale belonging to the oceanic dolphin family, of which it is the largest member. Course Hero is not sponsored or endorsed by any college or university. IN this picture, you can see a sea otter eating a sea urchin in a kelp bed. 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. The changes came after the 2010 death of SeaWorld … Sea otters are getting harder to find along the western part of the Aleutian chain. I think killer whales are eating sea otters because their primary food source may be scarce and they may be going to the second most abundant food sources, which may be affecting the overall population of sea otters. Some feed exclusively on fish, while others hunt marine mammals such as seals and other species of dolphin. Killer whales have been eating an unprecedented amount of sea otters … 7. 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.  I think killer whales are eating sea otters because their primary food source may be scarce and they may be going to the second most abundant food sources, which may be affecting the overall population of sea otters. Given that, prior to 1991, there had been no confirmed attacks by killer whales on sea otters, the discovery was puzzling. Let's get otter here! 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. The killer whale (also known as the orca) generally did not consume sea otters in the past, but now consumes thousands of otters. ... Sea otters eat invertebrates such as sea urchis, clams, crabs, etc. Scientists say killer whales off Alaska have begun hunting sea otters because their usual prey, seals and sea lions, have gone into serious decline. When he was on a cruise from Attu to Dutch Harbor in the early 1990s, Estes and his colleagues saw killer whales where they hadn't before, observations that later became a clue to the disappearance of the sea otters. Change then began to happen near shore when the killer whales began eating sea otters. "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.   Privacy Some biologists think the missing otters of western Alaska have disappeared to an unlikely place--the bellies of killer whales. By Environmental News Network staff. With less energy, there is less reproduction and more mortality, which leads to decreases in population size. Deprived of their normal food, killer whales turned to the sea otter. The killer whales have eaten more than 40,000 otters since the early 1990’s, leaving fewer otters to consume sea urchins from the ocean floor. The otter is much smaller than the sea lions and seals so the killer whales must eat … "We were seeing killer whales near the beach all the time," Estes said during a phone interview from his office in Santa Cruz, California. Killer Whales. But hungry killer whales aren’t finding enough of their preferred prey: seals and sea lions. More attacks witnessed since then. 1) 1st killer whale attack on sea otter observed. Explain why Killer whales are eating sea otters now There was most likely a decline in the populations of the killer whales usual prey. Alligators DON'T eat sea otters, Killer whales (orcas) do! clude that the sea otter population declines were caused by increased mortality. What do you think has caused the killer whales to start eating sea otters? 2) Contrasted decline in 2 aras. What do sea otters eat? Jim Estes, a wildlife research biologist who works for the U.S. Geological Survey at the University of California, has watched sea otters in Alaska since the 1970s. Let's get otter here! How do you think the sea otters are affecting these two groups of species? This preview shows page 2 out of 2 pages.   Terms. Please report any problems or feedback concerning this website to uaf-rcs@alaska.edu. Estes said the cause of the killer whales' change in menu may also be a natural warming of the ocean or some other change in ocean ecology. 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. Not only did we see killer whales but we started seeing 'em eating otters. A male killer whale would need to eat 5 (4.66) male sea otters or 7 (6.9) females per day. Killer whales are the largest predator of warm-blooded animals alive today.Globally, killer whales appear to have an extremely diverse diet. What do you think has caused the killer whales to start eating sea otters I, 19 out of 19 people found this document helpful. 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. 4. Three lines of evidence point to increased predation by killer whales (Oiecliis or-ca) as the reason for this mortality. During reading: What is causing the rapid loss of sea otters in Alaska? A female killer whale would need to eat 3 (3.1) male sea otters or 5 (4.6) females per day. Their calculations suggest that only four transient marine mammal eating killer whales would have needed to switch to an exclusive sea otter diet to account for the decline. John Dornellas, 37, filmed sea otter frantically swim towards his boat for safety Killer whales have not always preyed on sea otters. Sea otter being chased by a killer whale leaps to safety on a boat with just seconds to spare. However, these smaller urchins are a favourite food of sunflower stars. Try our expert-verified textbook solutions with step-by-step explanations. Specifically, it discusses the effects of killer whales eating sea otters in the North Pacific. Sea otter being chased by a killer whale leaps to safety on a boat with just seconds to spare. Researchers doing wildlife surveys following the Exxon Valdez oil spill and biologists studying otters in the Aleutians witnessed killer whales attacking sea otters. No. Killer whales mostly eat sea lions, seals, and other marine mammals that spend most of their time far offshore, away from sea otters. One killer whale with a taste for sea otters could eat more than 1,800 sea otters a year, Estes said. Yet, individual ecotypes or populations are often extremely specialized. This is an urban legend, as explained at Snopes.com. 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. By Environmental News Network staff. 7. The GI is located on the West Ridge of the University of Alaska Fairbanks campus. What is kelp and why is it important? 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. That decline in animals was happening mainly out in the ocean. Assignment #8 - Population and Community Ecology, Central Washington University • BIOLOGY 181, Georgia Institute Of Technology • BIOL 1502, Copyright © 2021. They feed on sea otters in means of survival that is survival of the fittest. These small urchins also readily devour kelp, and if their numbers swell, they begin to thin out kelp forests. Not only did we see killer whales but we started seeing 'em eating otters. Three lines of evidence point to increased predation by killer whales (Orcinus orca)asthe reason for this mortality. Deprived of their normal food, killer whales turned to the sea otter. On his 1990s cruises to the Aleutians, he and other biologists noticed a 25 percent decline in sea otters each year. 3. Killer whales are top-level predators in the ocean. At first, Estes didn't consider killer whales as a reason for the sea otter decline. 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. 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. 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. ©2020 Geophysical Institute, University of Alaska Fairbanks. In Alaska, the rapid loss of sea otters turns out to have a shocking cause. With the kelp forest gone it throws off the whole ecosystem because there ae many other species that depends on the kelp. October 19, 1998 Web posted at: 2:50 PM EDT. When the big whales got hard to … (The sea otter is an endangered species). Their population has dropped from about 53,000 animals in the early 1990s to only 6,000 today. 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. Orcas were eating otters because the really big whales they used to eat were nearly wiped out by commercial whalers back in the 1950s. 5. This suggests that four killer whales, feeding exclusively on sea otters, could have driven the population into decline. October 19, 1998 Web posted at: 2:50 PM EDT. As a result, the population of sea urchins has risen dramatically, and the sea urchins began eating kelp at an alarming rate. "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. In Clam Lagoon, the entrance from the open sea is too narrow and shallow for killer whales to get in. When the whales start to eat the otters the otter population starts to dwindle in numbers and then the sea urchins has the chance to multiply in number and then they start to devour the kelp forest. It was SeaWorld’s first show that did not include trainers in the water with the killer whales. Transient killer whale populations likely decreased as well, because the cost-benefit ratio of eating otters is less favourable, resulting in an overall worse energy trade-off for individual whales. However, it is true that the cost to clean and rehabilitate oiled sea otters was about $80,000 per animal. And they sometimes use rocks to break open their prey. What effects do you expect sea otters to have on the rest of the kelp forest community. in California, gathered anecdotes for a paper published in the October 1998 Marine Mammal Science. Course Hero, Inc. What might threaten sea otters? Is it true that two oiled seals were rehabilitated at a cost of $80,000 each and upon being released into the wild were promptly eaten by a killer whale? Their favorite prey has always been sea lions and seals. What caused the loss of sea otters along the coasts of Washington State and Oregon? 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. John Dornellas, 37, filmed sea otter frantically swim towards his boat for safety Humans also kill sea otters when they use fishing gear that traps the otter or hit the otter with boats. The Orca diet also consists fish, squid, seals, sea lions, dolphins, porpoises, and large whales such as the Blue Whale. What do you think has caused the killer whales to start eating sea otters? Killer whales have a diverse diet, although individual populations often specialize in particular types of prey. Orca Whales do eat penguins. Researchers say the actions of people may have caused this unusual switch in the diet of killer whales. So Estes looked at the history of … clude that the sea otter population declines were caused by increased mortality. No one had published a scientific paper on killer whale predation on sea otters until Brian Hatfield, also of the U.S.G.S. Since it was established by an Act of Congress in 1946, scientists at the Geophysical Institute have studied geophysical processes from the center of the Earth to the surface of the sun and beyond, turning data and observations into information useful for state, Arctic and national priorities. How do the otters keep warm? 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. "All of us commented on how peculiar that was.". Killer whales had not been known to … When sea otters are present, they eat a huge amount of sea urchins. In a recent Anchorage Daily News article, director Andy Rosenberg of the National Marine Fisheries Service said a link may exist between overfishing of pollock and the decline of the Steller sea lion, a killer whale prey species that has declined more than 70 percent since the 1960s. 10. How do we know for sure that killer whales feed on sea otters (3 reasons)? 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? 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. Sea otters do an excellent job of eating large sea urchins over eight centimetres in diameter, but they tend to leave behind smaller urchins. The otter is much smaller than the sea lions and seals, so the killer whales must eat more to get the same nourishment. What do these data tell you about the role of sea otters in their community? She wails after her baby is eaten by the huge predator. Otters are eaten by large predators, such as great white sharks, killer whales, bears, sea lions, eagles and coyotes, depending on their geographical location. Killer whales have started eating them. 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