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Spokane, Washington  Est. May 19, 1883

Older female orcas lead the group, study says

Melissa Healy Los Angeles Times

What does an ocean-going titaness do after she has the lost the ability to bear young?

Well, for starters, she goes on living – sometimes past the ripe old age of 90, while male orcas over 50 are dying off in droves. Throughout the animal kingdom, that is unusual enough.

But the menopausal female orca does more than survive, says a new study: She becomes an influential leader of younger orcas, honing the survival skills of her progeny – and their progeny – unencumbered by direct childcare duties of her own.

Quite the opposite of being a burden to her kind, her post-menopausal leadership role seems to make the older female orca her species’ evolutionary ace in the hole.

Published in the journal Current Biology, the new research finds that among orcas, females beyond their reproductive years become habitual leaders of collective movement – generally foraging movement – within their pods. Their position “on point” becomes particularly prominent in lean years, when salmon – the mainstay of the orcas’ diet – is scarce.

The new findings offer the first evidence that in certain species and under specific circumstances, females who live well beyond their reproductive years “act as repositories of ecological knowledge.”

The authors of the study are marine mammal researchers from the universities of York and Exeter in Great Britain and the Center for Whale Research in Washington state. To glean their findings, they analyzed 751 hours of video taken of Southern resident orcas during annual salmon migrations off the coast of British Columbia and Washington.