Killer whale mothers love their sons a lot.
So much so, say researchers, that they live longer just to protect them from harm.
Indeed, killer whale mothers have the longest period of menopause of any mammal in order to live longer to care for their adult sons.
Most mammals don't live much longer after their ability to reproduce is finished, making the killer whale an extraordinary exception (other than humans, which live longer after menopause).
Killer whales often live well into their 90s, but female whales stop reproducing in their 30s or 40s, said ScienceNow.
Researchers believe that the length of the whale's menopause, and her long lifespan afterwards, may be to protect their adult sons, which seem to die quickly after their mother dies.
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Oddly, the death of the mother does not affect their female offspring in any measurable way, said Red Orbit.
This despite young females also living with their mothers during their early life.
The mother's long life is believed to have evolutionary importance.
“For most animal species, the potential for an individual to increase the propagation of its genes stops when they stop reproducing,” study co-author Darren Croft told Discovery News.
“Our results show that, as with humans, female killer whales can continue to increase the propagation of their genes long after menopause.”
He added that "They do this by helping to increase the survival of their older sons, which in turn increases the number of grandchildren fathered by their sons."
The findings appeared in the journal Science.