The beloved orca is one of only a few mammals that are known to go through menopause.
Until recently, the reason for this was unknown.
New research now suggests its related to grandmothers boosting the survival of their grandkids.
It’s hard to measure how much we can benefit from our grandmothers influence.
They are full of all kinds of valuable life lessons they collated over years of wisdom and experience, this definitely rings true for orcas.
Scientists who analysed decades of orca populations found that young orcas that were with their grandmothers were more likely to stay alive than those without.
A calf’s risk of death dramatically rose for two years following the death of its grandmother.
This is because the orca societies are matriarchal, just like the elephants.
The older females carry with them crucial knowledge about food resources that can usually mean life or death for their kin.
The survival rates of young whales improve even more dramatically if the grandmother has already gone through menopause.
This fact alone is surprising since menopause is typically associated with the final stages of life.
Now though, it seems the added longevity humans and orcas seem to have after menopause serves an evolutionary purpose.
Grandmother orcas live long after they’re unable to produce their own offspring.
Their sheer presence helps ensure that children of their children grow up strong and healthy.
Orcas live in tight-knit family groups of up to 40 individuals.
The predators in the group work together to hunt a variety of prey from fish to whales, depending on where they live.
In general, both male and female orcas stay in their natal pods throughout their lives, although they search for mates from other pods to avoid inbreeding.
Orca females stop reproducing at around 40 and can to live to 90 whereas males tend to live only around 50 years.
“[An orcas grandmother’s] greater knowledge and their leadership, especially when times are hard, are helping calves,” says Dan Franks an evolutionary ecologist at the University of York in the U.K.
For their research, scientists analyzed decades of data on orca populations around Washington and British Columbia.
What they noticed was that orca calf mortality rose sharply in the years following the death of a post-menopausal grandmother.
On the contrary, calves that still lived with their grandmothers enjoyed a much higher rate of survivability.
“The study suggests that breeding grandmothers are not able to provide the same level of support as grandmothers who no longer breed,” says Dan Franks.
“This means that the evolution of menopause has increased a grandmother’s capacity to help her grand-offspring.”
“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.”
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