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） genetic¹ 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 bode² 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 coordinated³ by the International Whaling Commission.

The genetic survey revealed a "surprisingly high" level of diversity that may help the population slowly rebound⁴ 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," noted⁵ Sremba, who conducted the research as part of her master's degree with the Marine⁶ 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 overlapping⁷ generations may have helped retain the diversity."

"In fact," she added, "some of the Antarctic blue whales that survived the genetic bottleneck⁸ 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 Soviet⁹ whaling. Blue whales are thought to be the largest animals ever to have lived on Earth, said OSU's Scott Baker¹⁰, 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."