It's hard to measure how much we benefit from the influence of a grandmother.
Grandmothers have a wealth of wisdom and experience — and that translates into all kinds of valuable life lessons.
We're hardly the only species to value them. In fact, their generational influence may play a critical role in orca society.
A study published this week in the Proceedings of the National Academy of Sciences suggests the elder whales are a key factor in keeping their grandkids alive, especially when food is scarce.
The survival rates of those young whales improve even more dramatically if the grandmother has already gone through menopause.
That's particularly surprising since menopause among most animal species is typically associated with the tail end of life. Not so, however, with humans and some whales — including orcas, which can live decades beyond menopause.
Now, it seems that added longevity has an evolutionary purpose. Grandmother whales live long after they've stopped being able to produce their own offspring, and their continued presence ensures the children of their children grow up strong and healthy.
It takes a village, but especially grannies
For their research, scientists analyzed decades of census data on orca populations around Washington state and British Columbia. Orca calf mortality, they noted, rose sharply in the years following the death of a post-menopausal grandmother. But calves that still lived with their grandmas enjoyed a much higher rate of survivability.
The researchers suspect post-menopausal grandmothers simply have more time to dote on the young ones, caring for them as a kind of nanny and making sure they have enough food to eat.
"The study suggests that breeding grandmothers are not able to provide the same level of support as grandmothers who no longer breed," lead author Dan Franks, a biologist at the U.K.'s University of York tells Agence France-Presse. "This means that the evolution of menopause has increased a grandmother's capacity to help her grand-offspring."
Humans may recognize this phenomenon as the "grandmother effect": Women who retain their strength after the decline of fertility have traditionally helped their daughters care for the children.
"This is the first non-human example of the grandmother effect in a menopausal species," Franks adds.
"It has also been shown in elephants, but they are able to reproduce until the end of their lives. We currently know of only five species that go through menopause: the others are short-finned pilot whales, narwhals and beluga."
Now, how exactly does one know when a post-menopausal orca granny is spreading her life-affirming cheer to the rest of the pod?
The researchers looked at 378 individual whales known to have a maternal grandmother. In the cases where a grandmother had died within the previous two years, the mortality rate for a young whale jumped by 4.5 times.
And in times of food scarcity, the "grandmother effect" was particularly pronounced.
"We have previously shown that post-reproductive grandmothers lead the group around foraging grounds, and that they are important in doing that in times of need, when the salmon are scarce," Franks explains to AFP.
"They are also known to directly share food with younger relatives. We also suspect babysitting."