Quirks & Quarks

Giant silverback gorillas show a gentler side in looking after orphans

Long-term research on mountain gorillas show how the troop cares for orphaned or abandoned infants

Long-term research on mountain gorillas show how the troop cares for orphaned or abandoned infants

Silverback Bwenge takes care of orphans Ntaribi and Akaramata after the deaths of their mother (Dian Fossey Gorilla Fund)

Mountain gorillas come together as a troop to support young gorillas orphaned by the loss of their mother according to a long-term research study led by biologist Robin Morrison.

Morissson, a post-doctoral researcher with the Dian Fossey Gorilla Fund in Rwanda, and the Centre for Animal Behaviour at the University of Exeter in England, worked with observation of mountain gorillas begun in the 1960s by legendary gorilla research pioneer Dian Fossey.  Among the surprises in the work was the important role the large male silverback plays in taking care of the orphaned or abandoned youngsters.

Silverback Isabukuru grooms orphan Masunza (Dian Fossey Gorilla Fund)

The long-term observations showed it was relatively rare for young gorillas to lose their mothers. In the half-century of observations, a juvenile gorilla was left motherless about once a year in a population of about 300.

Mothers sometimes died of age-related natural causes, but on other occasions would leave their social group and abandon a child in order to take up with another group for better mating opportunities. For juvenile gorillas, the loss of a mother was thought to be especially hard because maternal nurturing continues well into adulthood.

But Morrison found gorilla families step up and take care of an orphan.

Orphans Fasha and Icyororo support each other while a silverback named Kubaha looks on (Dian Fossey Gorilla Fund)

It takes a gorilla village to raise a child

If they were older than two, when they are able to feed themselves, the motherless gorillas suffered no greater risk of dying early than those raised by their mothers.  They spent a lot of time with other juveniles, and other mother gorillas, who typically pay little attention to offspring that are not their own, would make an exception for the orphans. 

The biggest difference, however, was with the amount of attention that orphans would get from mature males, and in particular the dominant male silverbacks.  The silverbacks spent a lot of time resting with, grooming, and making sure the orphans were never isolated and always had enough to eat.

The silverback Titus looks after Ihumure. Ihumure's mother abandoned her child to join another group (Dian Fossey Gorilla Fund)

Over the long term, the motherless gorillas were found to have regular reproductive lives, and in at least one instance, become a leader within their new family group. 

Among the great apes, this behaviour is unique to gorillas and humans. 

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