Scientists have uncovered the evolutionary reason behind menopause in killer whales, a trait shared only with humans and short-finned pilot whales. Research led by the University of Exeter reveals that older female orcas stop reproducing because they lose out in competition with their own daughters.
The study, published in Current Biology, examined two killer whale populations off the coast of Canada and the US. It found that offspring of older mothers were 1.7 times more likely to die than those of younger females, due to competition for resources within the pod.
Professor Darren Croft of Exeter University explained: 'Our previous work shows older, post-reproductive females help their offspring survive, but that alone does not explain why they stop reproducing. Females of many species act as leaders in late life but still breed – elephants for example.'
The research highlights the role of older females as leaders, particularly in hunting salmon, their primary food source. The late matriarch Granny, or J2, was known for her ability to summon the pod by tail-slapping, even from miles away.
Co-author Dr Daniel Franks from the University of York added: 'If an old female killer whale reproduces, her late-life offspring suffer from being out-competed by her grandchildren. This, together with the help she provides to her existing family, makes it better for her to stop reproducing.'
