Why Killer Whales Live So Long After Menopause

Study: These matriarchs become essential group leaders
By Elizabeth Armstrong Moore,  Newser Staff
Posted Mar 6, 2015 9:21 AM CST
Why Killer Whales Live So Long After Menopause
Killer whales and short-finned pilot whales are the only species known to have post-reproductive life spans like our own.   (AP Photo/Center for Whale Research, David Ellifrit, File)

Female orcas typically stop breeding around the age of 40, which is roughly the time when their male counterparts tend to, well, die off. But once the females hit menopause, they can rather unusually live another 50 or so years—and now scientists think they know why. Because they've amassed critical survival skills, these matriarchs become essential group leaders, even venturing to the front of the pod during key hunts, scientists report in the journal Current Biology. "The value gained from the wisdom of elders can help explain why female killer whales and humans continue to live long after they have stopped reproducing," one researcher tells the Smithsonian. In their study, the researchers explain that "classic life-history theory predicts that menopause should not occur because there should be no selection for survival after the cessation of reproduction."

But killer whales and short-finned pilot whales are the two species known to have "postreproductive lifespans" that are similar to our own. In examining why that was the case with killer whales, scientists made use of 751 hours of video of orcas off British Columbia and Washington. They noted a "significant" relationship between the abundance of salmon (which makes up the lion's share of orcas' diet) and the female reproductive state. Specifically, when salmon were in short supply, older females were more likely to front the group. Per the study, "This finding is critical because salmon abundance drives both mortality and reproductive success in resident killer whales." (This orca mother was recently found dead, and then the news got worse.)

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