Survival of male orcas depends on older females, study shows

Sep 14, 2012

Researchers in the San Juan Islands say the survival of older female Orcas, after they go through menopause, helps younger males stay alive longer.

That might not surprise many humans, but scientists well-versed in the behavior of Orca whales say it’s a relatively new conclusion. And, in many species, females don’t live long after the end of their reproductive life.

Darcie Larson, a naturalist at the Seattle Aquarium, says she's seen this in the local J-Pod, with a male called Ruffles and his mother.

 “We called him a mama’s boy, with great affection, because he was almost always seen right next to his mother, Granny, who is the oldest whale, at about 101 years of age, we believe, ”  Larson says.

By helping sons survive, those sons are more likely to have their own offspring, which could lead to more longevity for the species, the researchers say.

Exactly how the females help is up for speculation. One idea could be revealed by work on decoding Orca calls like those captured by K.C. Balcomb. The squeaky calls are well known in the northwest. But it's not entirely understood whether all mother Orcas help their sons avoid danger or if they lead them as they forage for food.

"This finding may explain why female killer whales have evolved the longest post-reproductive life span of all nonhuman animals," according to the research published in the journal, Science.

More background can be found via the Center for Whale Research in Friday Harbor.