The vital role of whale grandmas
Post-menopause, they help young ones survive, study shows.
Female killer whales usually stop reproducing in their 30s or 40s, but like humans they can live for many decades following menopause.
And they are making good use of that time, it seems.
New research suggests grandmothers who are no longer able to reproduce have the biggest beneficial impact on the survival chances of their grandchildren, particularly at times when food is scarce.
A team from the Universities of York and Exeter in the UK, the US Centre for Whale Research, and Fisheries and Oceans Canada analysed data gathered over 36 years on two populations of resident killer whales off the North West Pacific Coast of North America.
The findings are published in the journal Proceedings of the National Academy of Sciences.
"The menopause has only evolved in humans, killer whales and three other species of toothed whales and understanding why females of these species stop reproduction well before the end of life is a long-standing evolutionary puzzle,” says Darren Croft.
"Our new findings show that, just as in humans, grandmothers that have gone through menopause are better able to help their grand offspring and these benefits to the family group can help explain why menopause has evolved in killer whales just as it has in humans."
The researchers are now using drones to directly study helping behaviour between family members in these killer whales.