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Male gorillas who babysit have five times more babies

When it comes to gorillas, the males who help females out with their infants get benefits. The benefits? More babies. A new study of male gorillas in the wild in Rwanda has found that those who spend the most time grooming infants and resting with them—others’ offspring as well as their own—have about five times more offspring than males who don’t help out with the little ones.

This is surprising, scientists say, because male caretaking isn’t usually considered a smart reproductive strategy in primate species where access to females is intensely competitive. Instead, researchers thought the most successful strategy for males would be to put more time and energy into outcompeting other males for a mate, as chimps do.

That strategy still works for many male gorillas, who dominate small harems of females. But in 40% of the groups of mountain gorillas studied at the Dian Fossey Gorilla Fund’s Karisoke Research Center in Volcanoes National Park in Rwanda there is more than one male in a group, sometimes as many as nine. And those males need to be resourceful to get a female’s attention.

It turns out the way to a mom’s heart is through her offspring, according to the new analysis, published today in Nature Scientific Reports. Genetic paternity data for 23 adult males and 109 infants, along with 10 to 38 hours of observations for each male gorilla, suggest the more time these “babysitters” spend with infants, the more reproductive success they will have. The findings could even have implications for the evolution of paternal care in humans, given that we are the only other ape species whose males are willing to help out with the kids.