Whales Prey On Sea Otters

Killer whales that normally hunt seals and sea lions are now feeding on sea otters creating an ecological crisis along the entire Aleutian island chain of western Alaska.

Researchers say the sudden loss of thousands of sea otters is causing a population boom in sea urchins that are stripping the undersea kelp forest. The researchers said the killer whale predation is the only explanation for the sudden drop in the sea otter population.

The whole coastal ecosystem in western Alaska is now affected, says James Estes, a marine ecologist with the U.S. Geological Survey and the University of California, Santa Cruz. "A wide array of species will be affected," he said. "Coastal fish, mussels, marine birds and other predators in the system could all be impacted."

Undersea beds of kelp have been reduced by 90 percent in some areas. "The kelp beds serve as a nursery for small fish and other animals," said Estes. "A lot of species depend on the kelp beds for their survival."

Normally, there is a delicate balance of life in the western Alaskan waters, with sea lions and seals feeding on fish and the killer whales preying on the sea lions and seals. Independent of that, sea urchins graze on the kelp beds while sea otters feed on the urchins. This keeps the urchin population in check.

Since the late 1980s the sea lion and seal population declined by 90 percent. Deprived of their normal food, killer whales turned to the sea otter.

The otter is much smaller than the sea lions and seals so the killer whales must eat more to get the same nourishment. Estes estimates a single killer whale will have to eat 1,825 otters a year to get its required nourishment.

At that rate, said Estes, it would take just four killer whales feeding only on sea otters to cause a crash of the sea otter population throughout most of the Aleutian Island chain.

Written by Paul Recer