Grandmother Orcas

[Recusant]

I'd seen headlines in at least a couple of different places along the lines of "Grandmother Whales Helping Their Families" and skipped over them, thinking "no doubt that's a cute story." As usual, curiosity got the better of me, and I finally clicked on one. Interesting stuff about orcas, but also about the evolution of menopause, which is rarer in mammals than I'd thought.

"Killer whale grandmothers boost survival of calves" | ScienceDaily

New research finds that killer whale grandmothers who were no longer able to reproduce had the biggest beneficial impact on the survival chances of their grand-offspring. This may be because grandmothers without calves of their own are free to focus time and resources on the latest generation, the researchers suggest.

[. . .]

The research team also found that grandmothers had a particularly important role in times of food scarcity, as the impact on a calf of losing a post-menopausal grandmother was highest in years when salmon was scarce.

Previous research has shown that post-reproductive female killer whales are the most knowledgeable and provide an important leadership role for the group when foraging in salmon grounds.

These benefits to the group may help to solve the long-standing mystery of why the menopause has evolved in some species of whales and in humans, the authors of the study say.

[Continues . . .]

[xSilverPhinx]

That's interesting. The evolutionary 'value' of older individuals who are no longer able to reproduce has been an interesting question. Though intuitively we know why they are still cared for in some animal species it seems like evidence supporting that hypothesis is recent.