Scientists Explain the Mystery Behind Killer Whale's Menopause
A new study may have finally uncovered the mystery behind why female killer whales experience menopause, just like humans, when they get older.
The study, published in the Current Biology, showed that older female orcas tend to put off their reproduction to give way for younger females that were more likely to mate and reproduce. Additionally, the researchers found that the level of relatedness of killer whales in a single pod might also be a driving factor in the menopause of older females.
"When females are born, they have a relatively low relatedness to the males in their group, because their father isn't around," explained Darren Croft, a professor of animal behavior at the University of Exeter in England and one of the authors of the study, in a report from New York Times. "But as a female starts to reproduce, her relatedness to males increases, because her sons stay with her."
Killer whales are just one of the three species of mammals that are known to undergo menopause, the other two are humans and short-finned pilot whales. Orcas could live for 90 years or even longer. However, female orcas experience menopause between 30 and 40 years old.
For the study, the researchers analyzed over 43 years of demographic data of two killer whale populations in the northwest Pacific. Killer whale groups are matriarchal, which means sons and daughter live with their mother throughout their life. Due to this, older females in the pod become more related with the other members, while younger females are less related with the pod. This could mean that younger females could secure more resources for herself and her future offspring, while the older females are more likely to cooperate, sharing resources and knowledge.
If by chance an older female in the pod gives birth simultaneously with a younger member, their calves will be 1.7 times as likely to die in the first 15 years of life compared to those calves that are born to the younger mothers.