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Many human grandmothers love to spoil their grandchildren with attention and treats, and for good reason: Studies have shown that having a living grandmother increases a child’s chance of survival. Now, new research shows the same may be true for killer whales. By providing young animals with some freshly caught salmon now and then—or perhaps with knowledge on where to find it—grannies increase their grand-offspring’s chance of survival.
The new study is the first direct evidence in nonhuman animals of the “grandmother hypothesis.” The idea posits that females of some species live long after they stop reproducing to provide extra care for their grandchildren.
Cetaceans - Life - Stage - Kristen - Hawkes
“It’s very cool that these long-lived cetaceans have what looks like a postfertile life stage,” says Kristen Hawkes, an anthropologist at the University of Utah in Salt Lake City who has dedicated much of her career to studying the grandmother effect; she was not involved in the new study.
Women usually go through menopause between ages 45 and 55, even though they may live to age 80, 90, or older. Studies in modern-day hunter-gatherer communities as well as in populations in Finland and Canada show that older women can help increase the number of children their daughters have, and boost the survival rates of their grandchildren. Dan Franks, a computer scientist and biologist at the University of York in the United Kingdom, wanted to know whether this grandmother effect occurs in other species as well.
Franks - Colleagues - Data - Groups - Killer
Franks and his colleagues analyzed survival data from two groups of killer whales off the coast of Washington state and British Columbia in Canada that have been surveyed for decades. They used underwater cameras that allow scientists to identify individual whales by their distinctive markings and follow them as they age.
Among the more than 700 whales in the two groups, Franks was able to find...
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