With the exception of humans, menopause only occurs in killer whales – but why?

With the exception of humans, menopause only occurs in killer whales – but why?

When you think of unique animal traits, squids that can squirt ink or chameleons that can change color might come to mind. But do you know what’s really special about the animal kingdom? menopause. “Menopause is rare in nature,” he says. Charlie Grimes, an animal behaviorist at the University of Exeter (UK). Only six species – humans and five species of killer whales – survive past their fertile period.

Orcas and menopause

To see the evolutionary advantages of orcas living past menopause—after all, other animals die after their reproductive years— Killer whales Extensive research.

Grimes and her colleagues were able to work out the role of the older females in the herd, and thus their evolutionary benefit: protecting their offspring from injury when fighting off other orcas. The researchers did this by looking at how deep the tooth marks and scars on the fins were.

which reveals half a century of data on scars

the study, Published in the scientific journal Current Biology, focuses on Southern Resident Orcas, a group of endangered orcas off the Pacific coast of the United States. Killer whales are talented predators, and since this group is at the top of the food chain, the animals are not injured by their prey attacks.

The Cetacean Research Center has been collecting information about this group of killer whales for 47 years and has nearly 7,000 photographs of the 103 residents. Researchers know each orca so well that they can identify it by its dorsal fin and the white pattern behind it, called the saddle patch. They found that males whose mothers were no longer reproducing had fewer and deeper wounds than males whose mothers were still reproducing.

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There were no differences between males who had mothers of childbearing age and males without mothers in the group. It’s very likely that fertile mothers are “busy taking care of the young,” she says Deborah GilesDirector of Science and Research at the non-profit organization Wild Orca. Older females are said to “have more time and attention” with their older offspring.

Why do only children get special treatment?

This study also found that older mothers only made an effort to protect their sons, not their daughters. Previous research in the same population has shown that older female orcas continue to play an important role in matrilineal orca society on other fronts as well.

In this way, these females lead their flock to important feeding grounds, a particularly important role in times when salmon, the animals’ main prey, are present. the killer whale, hard to find. The mothers bite the salmon in half and give one half to their son, whom they continue to feed well into adulthood, while the daughters become more independent as they reach sexual maturity.

Daughters and sons remain with the troop throughout their lives, but males may mate with several females outside the group. This means that the care of his offspring will eventually fall into that other mess. This also gives the mother a greater chance of passing her genes on to her sons than to her daughters. Thus, males have a greater reproductive capacity than females Females prefer to mate with older and older malessays Giles. “If troops can keep their males well fed and away from conflict, the males will have a better chance of growing big and big.”

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