Researchers studying killer whales have made a discovery unusual in the animal kingdom: Grandmothers rock. That is, older female orcas make a big difference when it comes to the survival of their grandchild calves, according to the study in the Proceedings of the National Academy of Sciences. Orcas are one of a handful of mammal species (humans are another) whose females live long after their childbearing years are over, notes National Geographic. The new research makes the case that this menopause serves a purpose for the whales: The grandmothers, freed from the demands of raising their own offspring, share their food with the second generation and teach them how to forage for themselves. A telling stat: Calves are far more likely to die if their grandmothers are not around, especially in times of scarce food, per the Washington Post.
"Post-reproductive grandmothers use their superior ecological knowledge to lead their group around foraging grounds," Daniel Franks, lead author of the study from the University of York, tells Business Insider. The research team based their findings on 40 years of whale census data about orcas living off the coasts of Washington state and British Columbia. They suspect that grandmother orcas are doing more than simply providing food and foraging knowledge to the calves, suggesting that a phenomenon known as the "grandmother effect" in humans applies to the orcas as well. And the benefits appear to be long-lasting: “The grandmother effect that we have shown also appears to impact whales for their entire lives,” says Franks. (Read more killer whales stories.)