More than 99 percent of Antarctic blue whales were killed by commercial whalers during the 20th century, but the first circumpolar（极地附近的） genetic study of these critically endangered whales has found a surprisingly high level of diversity among the surviving population of some 2,200 individuals. That, says lead author Angela Sremba of Oregon State University, may bode well for their future recovery.

Results of the study have just been published in the open-access journal, PLoS ONE. As part of the study, the researchers examined 218 biopsy samples collected from living Antarctic blue whales throughout the Southern Ocean from 1990 to 2009, through a project coordinated by the International Whaling Commission.

The genetic survey revealed a "surprisingly high" level of diversity that may help the population slowly rebound from its catastrophic decimation（大批杀害） by whalers.

"Fewer than 400 Antarctic blue whales were thought to have survived when this population was protected from commercial hunting in 1966," noted Sremba, who conducted the research as part of her master's degree with the Marine Mammal Institute at OSU's Hatfield Marine Science Center. "But the exploitation period, though intense, was brief in terms of years, so the whales' long lifespans and overlapping generations may have helped retain the diversity."

"In fact," she added, "some of the Antarctic blue whales that survived the genetic bottleneck may still be alive today."

Prior to whaling Antarctic blue whales were thought to number about 250,000 individuals -- a total that dwindled（减少，变小） to fewer than 400 animals by 1972 when blue whales were last killed by illegal Soviet whaling. Blue whales are thought to be the largest animals ever to have lived on Earth, said OSU's Scott Baker, associate director of the Marine Mammal Institute and an author on the study -- and the Antarctic blue whales were even larger than their cousins in other oceans.

"These animals are very long-lived -- maybe 70 to 100 years -- and they can grow to a length of more than 100 feet and weigh more than 330,000 pounds," he said. "There is a jawbone（颚骨） in a museum in South Africa that takes up most of the lobby. This is one reason they were so intensively exploited; they were the most valuable whales to hunt."