Whose the daddy Gorilla?

With television shows  emotionally uniting children with their long-lost 'real fathers', paternity clearly matters to us humans. Many species show discrimination in rearing their own offspring.  But, it appears not to matter so much to mountain gorillas.


Gorilla Fathers from Dian Fossey Gorilla Fund on Vimeo.

Recent research published in the journal Animal Behaviour shows that being the biological daddy isn’t so important for male gorillas when it comes to their relationships with the youngsters in the group. What matters is their rank.

Mountain gorillas (Gorilla beringei beringei) live in groups in the forests of central Africa.  They are unusual among primates because one group, or troop, of gorillas can have more than one male, as well as several females.  So, do the males behave differently to the youngsters in the group? Or do they treat them all the same?  Is there any sign they are distinguishing their 'own' young?

Rank more important than genetic parentage  

The researchers tracked the way male mountain gorillas interact with infants to see if their behaviour is similar to other primates that live in troops with more than one male. The results show that being the biological father does not influence the way male gorillas interact with infants.

Primates like chimpanzees that live in troops with more than one male have a way of recognising which infants belong to which males. For animals that live in groups with only one male this is not necessary, as the male is most likely to be the father of all the infants in the group. The researchers wanted to determine whether gorillas have evolved a way of recognising their own offspring or father.

The researchers followed gorillas in Volcanoes National Park, Rwanda, and monitored the way the males and infants interacted. They looked at the amount of time the gorillas spent grooming each other and playing, and noted every ten minutes which gorillas were physically close to one another. They also looked at which males were dominant in the group.

The researchers analysed more than 1500 hours of data and found that there is no evidence to suggest that gorillas recognise their own offspring or father. Or at least if they do it doesn't affect the way they interact. 

Dominant males are gentle and nurturing 

Instead, they found that a male gorilla’s dominance or social rank had a stronger influence on its relationships with infants; alpha males tend to be more nurturing and have stronger relationships with infants in the troop. While statistically they are most likely to be the father, many infants are also sired by other males, but this doesn't affect they way they are treated.

“When we think of a human alpha male, we have a very specific set of cultural norms that go along with that, like aggression and not being very paternal,” says lead researcher Dr. Rosenbaum.

In gorillas, dominant males are often the biggest in the group, but they are gentle and nurturing with the infants.

Mountain gorillas are not only capable of living in multi-male groups, they may actually benefit from doing so. Advantages to living in multi-male groups include better female retention, since females seem to prefer multi male groups, and lower risk of infanticide.     

There are also clear benefits to the offspring. Infants in multi male groups are still generally safe even if the dominant male dies, since other males in the group can deter infanticidal outsiders.

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