Menopause is no one’s friend. Luckily for most of the animal kingdom, there are only three known species that experience it. Or to put that another way, there are only three species on the planet that continue to live long after they stopped reproducing: humans, pilot whales, and orcas.
Orcas start reproducing around age 15 and can live for up to 100 years, but they typically stop reproducing in their 30s or 40s. Generally, animals reproduce for their whole lives, and it was unclear why orcas are one of the few animals that don’t follow that pattern.
Now, an international research team found killer whales go through menopause due to conflict between mothers and daughters.
Researchers from the Universities of Exeter, Cambridge, and York, the Center for Whale Research, and Fisheries and Oceans Canada found that when older females reproduce alongside their daughters, the older female’s young calves are 1.7 times more likely to die than the younger female’s. Evolutionarily, it makes more sense for the older females to stop reproducing and, instead, focus their energy on helping the younger generation thrive.
“Females of many species act as leaders in late life but continue to reproduce, but this new research shows that old females go through the menopause because they lose out in reproductive competition with their own daughters,” explained the University of Exeter’s Darren Croft.
The main reason for this “reproductive conflict” is that orca families share food. They forage together and the mothers help their young get enough to eat.
Learning more about the factors that contribute to the survival and reproductive success of orcas is important to future conservation efforts — especially for the highly endangered Southern Residents who were studied for this research.
Croft says the bottom line is that “menopause is no accident.” It has evolved over generations of competition and cooperation in family groups.
To learn more:
- Read the Exeter news release: Mother-daughter conflict between killer whales can explain the evolution of menopause
- Read more about menopause in the rest of the animal kingdom: Do Animals Have Menopause?
- Find out why orcas go through menopause, but elephants don’t: Why Killer Whales Go Through Menopause But Elephants Don’t
- Read the full study: Reproductive Conflict and the Evolution of Menopause in Killer Whales
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