Killer whales and humans are among the very few animals that undergo menopause. Researchers have been trying to figure out
how menopause relates to orca social structure:
Pods are matrilineal, composed of old females, their offspring and their daughters’ offspring. There aren’t many old males, Croft said, because there’s a huge disparity in life expectancy, with males living to about 40 and females up to around 100.
At about the same age that the males expire, female killer whales go through menopause. The only other female mammals known to have long post-reproductive lives are pilot whales and humans. Most other animals reproduce until they are near death.
Fatherhood is not part of whale life. Neither is bonding between mates. Males will mate with females in neighboring pods but stay with their own families. The supreme, permanent bond in killer whale society is between mothers and their sons. All offspring stay with their moms throughout life, but the mothers put more energy into caring for the sons. Research in 2012 showed that males tend to die shortly after their mothers die. In 2015, researchers published observations that the older females lead their pods to find the most promising hunting grounds.
Among the whales, menopause seems to get older whales to focus on helping their growing offspring, especially their sons, find food and reproduce:
In some species, individuals are more likely to propagate their genes if they have fewer offspring but invest more in their survival and their success in reproducing. One of the most popular ideas to explain human menopause is the so-called grandmother hypothesis, which posits that older women keep promoting their genetic legacies by helping with grandchildren. In whales, it looks like the older females help the whole pod, which is made up of their kin. They also invest time in helping their grown sons find food, which could be a way to ensure that they have more grand-offspring.
Of course in humans some men also lead very long lives, which also needs explanation. In some societies at least older women and men serve as repositories of knowledge; for example old people may remember storms or droughts of rare severity, so the lessons of survival are not lost.
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