King Kong Cares: The Most Successful Male Gorillas Look After all Children

Male mountain gorillas who care for all infants in their group regardless of whether they're related have more children of their own over their lifetime.

2-year old mountain gorilla. Credit: Charles J Sharp / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0)

Broadly speaking in the animal kingdom, it is more beneficial in terms of reproductive success for males to invest more in mating than in parenting. In certain Old World primates however, such as baboons, macaques, gorillas and of course humans, males do look after their own offspring in order to help them survive. After all, it's all very well mating a lot but if the product of that doesn't survive to mate themselves, you've not done such a good job of passing on your genes.

Some scientists have also hypothesised that males might look after infants, their own or otherwise, in order to be more more attractive to females, but up to this point there has not been much evidence that this translates directly into increased reproductive success.

Male mountain gorillas commonly interact with infants in their group and do not seem to discriminate according to whether they're their own kin or not. Using data from the Dian Fossey Gorilla Fund’s Karisoke Research Center in Rwanda going back to 1967, a team of biological anthropologists from the US and Germany set out to work out why.

They discovered that even controlling for factors such as rank, age and mating opportunities, males who affiliated (groomed and rested in contact) with all infants had more offspring than those who affiliated with fewer infants. The males in the top third of male-infant interaction had more than 5 times as many offspring as males in the bottom third over the course of their reproductive life.

This is the first study directly linking male-infant affiliation with reproductive success in a promiscuous mammal and supports the idea that female gorillas are more likely to mate with males that interact the most with infants. The authors suggest that future work should look at whether higher male-infant affiliation corresponds to greater investment in and therefore higher survival of their own offspring.

https://doi.org/10.1038/s41598-018-33380-4

Rosenbaum, S., Vigilant, L., Kuzawa, C.W. et al. Caring for infants is associated with increased reproductive success for male mountain gorillas. Sci Rep 8, 15223 (2018).

Update 30th May 2020: If you want to find out more about this, the first episode of Primates on BBC iPlayer discusses this behaviour in more detail (and is a brilliant programme in general).