This is true even after controlling for other very important factors, such as how long the male lived and what dominance rank he held. Our models show that, across the course of their lives, males who do the most grooming and resting with infants are expected to sire about five times as many infants as the males who do the least. In total, we included data from 23 males, who collectively sired 109 infants. We recorded what percentage of each male’s time he spent grooming and resting with infants. The studyįor our study we used 30 years of genetic paternity data to determine which males sired which infant, and compared that to hundreds of hours of data on their behaviour. They have the behavioural and physical characteristics of a species where males are expected to invest their energy in finding mating opportunities, not bonding with infants. This is a notable finding, since mountain gorillas are not a species in which scientific theory predicts this sort of behaviour, much less a connection to the males’ eventual reproductive success. We found that the gorillas who spent the most time with any young, not just their own, also sired the most infants. In a recent study, my colleagues and I set out to determine why this might be the case, since this behaviour didn’t seem to only benefit their own infants.
Some regularly hold, play with, groom, and let infants sleep in their nests with them. From the time that young gorillas are old enough to move away from their mothers, they follow males everywhere.
ARE SILVERBACK GORILLAS MALE OR FEMALE FULL
Though mountain gorilla groups are full of complex social dynamics, just as human families are, in many groups some of the strongest social bonds we observe are between adult males and infants – even when the infants aren’t the males’ own offspring. Mountain gorillas, found in the mountains of Rwanda, Uganda and the Democratic Republic of Congo, are among the exceptions to the rule. Over time, natural selection favours males who use this strategy, so fathering behaviour rarely gains an evolutionary foothold. Simply put, male mammals that spend their time producing more infants rather than taking care of the ones they have will leave behind more offspring. Scientists believe the reason so many male mammals don’t get involved in caring for their young is because they get higher “returns on investment” if their energy is spent seeking out more mating opportunities rather than actively parenting. But these species are the exceptions, not the rule. There are also a number of South American monkey species where males take on equal or greater childcare burdens than females. Humans fall into that category, along with species like mice and lions. Scientists have identified more than 6,000 mammal species, but paternal care only occurs in 5 to 10% of them. Paternal care – where fathers care for their children – is rare among mammals (that is, animals which give birth to live young).
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