Why Grandma is in Charge: Female Killers Whales Become Pod Leaders After Menopause

When it comes to whales, grandma may be in charge. Scientists have found that menopausal female killer whales not only serve as key leaders, but also live almost twice as long as males. Now, scientists may have an answer as to why this is the case.

Menopause is a bizarre trait among animals-and also whale. Outside of humans, only the female members of two whale species outlive their reproductive lives in such a major way.

"Menopause is one of nature's great mysteries," said Lauren Brent, one of the researchers, in a news release. "Our study is the first to demonstrate that the value gained from the wisdom of elders may be one reason female killer whales continue to live long after they have stopped reproducing."

It's important to understand that evolution is all about reproduction and survival. Traits that enable individuals to pass more of their genes onto the next generation win out. Keeping this in mind, menopause seems to be a strange phenomenon, since it means females live for decades beyond their ability to pass on their genes.

New research, though, may have an explanation for this occurrence. The scientists collected data with the Center for Whale Research over 35 years. They also observed 102 individual killer whales in the wild. This data included birth and death rates, as well as genetic and social relationships between whales.

The scientists then added fisheries data on salmon abundance into the mix. Surprisingly, they found that post-reproductively aged females were especially strong group leaders in years when salmon availability was low. This suggests that the origin of menopause in humans may have a similar explanation; longer-lived females help ensure the survival and reproductive success of their younger kin by sharing their knowledge that they've accumulated over the years.

"In humans, it has been suggested that menopause is simply an artifact of modern medicine and improved living conditions," said Darren Croft, one of the researchers. "However, mounting evidence suggests that menopause in humans is adaptive. In hunter-gatherers, one way that menopausal women help their relatives, and thus increase the transmission of their own genes, is by sharing food. Menopausal women may have also shared a key commodity: information."

The findings are published in the journal Current Biology.

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