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. 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. What effects do you expect sea otters to have on the rest of the kelp forest community. 7. 2) Contrasted decline in 2 aras. The changes came after the 2010 death of SeaWorld … 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 … Let's get otter here! Privacy 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? Course Hero is not sponsored or endorsed by any college or university. No one had published a scientific paper on killer whale predation on sea otters until Brian Hatfield, also of the U.S.G.S. Killer whales are the largest predator of warm-blooded animals alive today.Globally, killer whales appear to have an extremely diverse diet. ©2020 Geophysical Institute, University of Alaska Fairbanks. With the kelp forest gone it throws off the whole ecosystem because there ae many other species that depends on the kelp. 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. 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. Killer whales had not been known to … Try our expert-verified textbook solutions with step-by-step explanations. 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. On his 1990s cruises to the Aleutians, he and other biologists noticed a 25 percent decline in sea otters each year. Why do orcas eat sea otters? 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. More about Sea otter being chased by a killer whale leaps to safety on a boat with just seconds to spare. An otter is “no more than a mouthful” for a killer whale, Bowlby says. What do you think has caused the killer whales to start eating sea otters? Some biologists think the missing otters of western Alaska have disappeared to an unlikely place--the bellies of killer whales. A mother otter clambers onto a motorboat in Tutka Bay, Alaska as the white underside of a killer whale chases after her. IN this picture, you can see a sea otter eating a sea urchin in a kelp bed. Find answers and explanations to over 1.2 million textbook exercises. What do these data tell you about the role of sea otters in their community? Otters are eaten by large predators, such as great white sharks, killer whales, bears, sea lions, eagles and coyotes, depending on their geographical location. The killer whale (also known as the orca) generally did not consume sea otters in the past, but now consumes thousands of otters. in California, gathered anecdotes for a paper published in the October 1998 Marine Mammal Science. 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. One killer whale would need to eat 1,825 otters a year to live. John Dornellas, 37, filmed sea otter frantically swim towards his boat for safety However, it is true that the cost to clean and rehabilitate oiled sea otters was about $80,000 per animal. When sea otters are present, they eat a huge amount of sea urchins. The whale sightings in shallow waters frequented by sea otters coincided with a nosedive in the population of harbor seals and Steller sea lions, but Estes said he was skeptical about the killer whale-sea otter connection. "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. That decline in animals was happening mainly out in the ocean. What caused the loss of sea otters along the coasts of Washington State and Oregon? Estes and his colleagues estimate that a single killer whale will have to eat 1,825 otters a year to get its required nourishment. This suggests that four killer whales, feeding exclusively on sea otters, could have driven the population into decline. No. In Clam Lagoon, the entrance from the open sea is too narrow and shallow for killer whales to get in. Researchers doing wildlife surveys following the Exxon Valdez oil spill and biologists studying otters in the Aleutians witnessed killer whales attacking sea 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. These small urchins also readily devour kelp, and if their numbers swell, they begin to thin out kelp forests. 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. clude that the sea otter population declines were caused by increased mortality. 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. Their favorite prey has always been sea lions and seals. Alligators DON'T eat sea otters, Killer whales (orcas) do! 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. Why have sea otters been compared to teddy bears? Sea otters are getting harder to find along the western part of the Aleutian chain. 4. 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. 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? The Orca diet also consists fish, squid, seals, sea lions, dolphins, porpoises, and large whales such as the Blue Whale. However, these two have experienced a significant decline in their population. More attacks witnessed since then. 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. By Environmental News Network staff. Orca Whales do eat penguins. Killer whales mostly eat sea lions, seals, and other marine mammals that spend most of their time far offshore, away from sea otters. Why the killer whales changed their diet is still a matter of speculation, but people may be the culprits. And they sometimes use rocks to break open their prey. October 19, 1998 Web posted at: 2:50 PM EDT. Killer whales have a diverse diet, although individual populations often specialize in particular types of prey. At first, Estes didn't consider killer whales as a reason for the sea otter decline. One killer whale with a taste for sea otters could eat more than 1,800 sea otters a year, Estes said. As a result, the population of sea urchins has risen dramatically, and the sea urchins began eating kelp at an alarming rate. A male killer whale would need to eat 5 (4.66) male sea otters or 7 (6.9) females per day. Terms. Assignment #8 - Population and Community Ecology, Central Washington University • BIOLOGY 181, Georgia Institute Of Technology • BIOL 1502, Copyright © 2021. 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. Humans also kill sea otters when they use fishing gear that traps the otter or hit the otter with boats. However, these smaller urchins are a favourite food of sunflower stars. October 19, 1998 Web posted at: 2:50 PM EDT. 7. What do you think has caused the killer whales to start eating sea otters? This is important because the sea urchins eat the kelp. Specifically, it discusses the effects of killer whales eating sea otters in the North Pacific. The otter is much smaller than the sea lions and seals so the killer whales must eat … They feed on sea otters in means of survival that is survival of the fittest. Killer whales have not always preyed on sea otters. 10. 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. 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. Yet, individual ecotypes or populations are often extremely specialized. Three lines of evidence point to increased predation by killer whales (Oiecliis or-ca) as the reason for this mortality. Alaska Science Forum article has no image, a placeholder has taken its place. But hungry killer whales aren’t finding enough of their preferred prey: seals and sea lions. 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. One reason for his doubt was that in several decades of going to sea and observing otters, he had never actually seen a killer whale eat a sea otter. Please report any problems or feedback concerning this website to uaf-rcs@alaska.edu. In Alaska, the rapid loss of sea otters turns out to have a shocking cause. 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. Given that, prior to 1991, there had been no confirmed attacks by killer whales on sea otters, the discovery was puzzling. John Dornellas, 37, filmed sea otter frantically swim towards his boat for safety The GI is located on the West Ridge of the University of Alaska Fairbanks campus. 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. With less energy, there is less reproduction and more mortality, which leads to decreases in population size. When the big whales got hard to … Orcas were eating otters because the really big whales they used to eat were nearly wiped out by commercial whalers back in the 1950s. 3. Not only did we see killer whales but we started seeing 'em eating otters. During reading: What is causing the rapid loss of sea otters in Alaska? ... 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