As they documented more attacks, they began wondering why a 10-ton orca would waste its energy on a 65-pound sea otter. 2). The Navy estimates the southern population of killer whales in the Puget Sound region could be subject to the non-lethal take two to 51 times a year during the seven years of Navy activity. Approximately 2,500 killer whales live in the eastern North Pacific Ocean—home to the most well-studied killer whale populations. Mr. DeMASTER: The people who really know killer whales, who spend their lives following them around and studying them--they just don't find any evidence that large whales are an important part of their diet. They can tell, even in the darkest parts of the sea, where items are by how quickly their noises bounce back. Orcas have mostly black skin with white patches. Courtesy of J.P. Sylvestre Ecologists say killer whales are eating the otters. The whales were smaller than other killer whales, and they had rounded heads and pointier fins. A new theory suggests a massive decline in seals, sea lions and sea otters in the North Pacific may have been triggered by over-fishing of great whales. I should point out that killer whales around the world are doing fine, but this population is listed as endangered on both sides of the border of the U.S. and Canada. SCIENCE. A group of ecologists says it has solved the mystery of Alaska's missing sea otters. First, Williams determines that the average orca needs to eat the equivalent of five to seven sea otters a day just to get by. ", It was a slow start. NIELSEN: Williams says it's hard to overstate how much these findings upset people who all but worship killer whales. But not everyone is buying the theory. What might threaten sea otters? PCBs first came under scrutiny in the 1970s, when birds, seals, and otter populations began rapidly decreasing. "This was a very different-looking group of killer whales," says Robert Pitman, a marine ecologist with the National Oceanic and Atmospheric Administration. NIELSEN: Environmental groups say the orca paper does a disservice to the cause of conservation by diverting attention from what they say is the real problem in the Bering Sea: overfishing. These giant pectoral fins come up on either side of the sea otter. Whale researchers spotted a baby orca swimming energetically with its mother west of San Juan Island on Friday. NIELSEN: DeMaster is director of the federal government's Alaska Fisheries Science Center. The chemicals were affecting their ability to reproduce. Either way, the mystery killer whales of the Southern Ocean have been found. Local fishers had been complaining that some kind of whale was stripping fish off their lines. (B) Global overview of PCB concentrations in killer whale blubber (ppm, parts per million).Light and dark green circles represent males and females, respectively. In recent decades, several populations of killer whales have declined and some have become endangered. When the big whales got hard to find, Williams says, the orcas switched to big, stellar sea lions and then to medium-sized seals. (The sea otter is an endangered species). "And most importantly," Pitman adds, "they had a little tiny eye patch," a white spot under each eye characteristic of killer whales. But Jim Hasties, a federal biologist and a major proponent of the orca theory, says there is one solution that almost everyone can agree on: continuing efforts to rebuild the region's stocks of great whales. Killer whales in the north Pacific switched to eating Harbor seals, Northern fur seals, Steller sea lions, and finally Sea otters, thinning each species’ populations out one-by-one. Many people are trying to figure out why. Although the future looks grim for the otters at the moment, there is some hope on the horizon. Ms. TERRY WILLIAMS (University of California at Santa Cruz): It's a bizarre way of hunting, where these killer whales have learned to swim upside down, below a sea otter that's resting on the water's surface. This is due to the fact that killer whales are used to eating animals two to five times the size of otters, so they need to eat two to five times as many otters as seals or sea lions. Killer whales have a diverse diet, although individual populations often specialize in particular types of prey. And baby makes 75: newborn orca boosts endangered whale population. Different populations of killer whales make different vocalizations, and different pods within these populations may even have their own dialect. affected. NIELSEN: Williams is part of a team that first observed these sneak attacks seven years ago when they were studying the otter die-off along the Aleutian Islands. Second, we evaluated the impact of killer whales on sea otter populations at Adak Island by contrasting otter population trends and sur-vival rates between Clam Lagoon, an area uniquely inaccessible to killer whales, and ad-jacent Kuluk Bay, an open coastal environment (Fig. Some feed exclusively on fish, while others hunt marine mammals such as seals and other species of dolphin. It's one of those moments that biologists live for. For Pitman, the hunt was on. Before reading: Describe a sea otter. This is ALL THINGS CONSIDERED from NPR News. 1 Global PCB concentrations in killer whales. People raised on movies like "Free Willy" tend to think of killer whales as well-meaning, fence-jumping giants who want nothing more than to live in perfect harmony with all the other creatures in the ocean. NIELSEN: But it's not just whale-huggers who hate the orca hypothesis. And I said, 'That's it! Marine scientists suggest the Southern Resident orcas face problems centered on their diet. I'm Michele Norris. The team had lowered an underwater microphone over the side on a long cable, with cameras attached. Orcas were eating otters because the really big whales they used to eat were nearly wiped out by commercial whalers back in the 1950s. He also says the original idea that these orcas once ate the great whales can't be proven. Since 1990, otter populations off the Aleutian Islands have fallen by as much as 80 percent. Question Sheet: Sea Otters, Kelp, and Killer Whales. Serious scientists, like Doug DeMaster, don't think much of it either. And by the late 1990's, I'd see 'em three or four times a day. "This study was really a decade-long look at what do killer whales die from, from California to Alaska all the way out to Hawaii," he sasy. 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