Killer whales slaughter sea otters

THE SEA OTTER, nearly driven to extinction earlier this century, is being threatened by a new enemy - killer whales.

Scientists say killer whales off Alaska have begun hunting sea otters because their usual prey, seals and sea lions, have gone into serious decline.

Killer whales had not been known to attack sea otters until marine biologists noticed an incident in 1991.

Jim Estes, a biologist at the US Geological Survey and the University of California, Santa Cruz, describes in the journal Science how hungry whales have slaughtered the region's population of sea otters, which have declined by about 25 per cent a year since 1990. "We estimate that between 40,000 and 45,000 sea otters have died since 1990 in roughly 3,300 kilometres (2,050 miles) of shoreline," he said.

The usual diet of killer whales is stellar sea lions and harbour seals, both of whose populations have seriously declined in the North Pacific. A decline in fish stocks from overfishing has been blamed.

One killer whale would need to eat 1,825 otters a year to live. This suggests that four killer whales, feeding exclusively on sea otters, could have driven the population into decline.