A study of mountain gorillas by the Dian Fossey Gorilla Fund has pored through more than 50 years of data to reveal how these great apes respond to the loss of a mother gorilla within a community. The study has concluded that when young gorillas lose their mother, other members of the group will come together to fill the gap, enhancing their bond with the orphaned gorillas and supporting them.
“In many species, like our close relatives, chimpanzees, individuals without mothers suffer higher mortality or may be less successful parents themselves, and this finding can hold even if the loss occurs in early adulthood,” said study lead author Dr Robin Morrison in a press release. “But our research shows that mountain gorillas really go against this trend.”
Whilst infant gorillas are nutritionally dependent on their mother until they are just over three years old, if a mother gorilla died or left the group after this point, there was no discernable impact on survival of the orphaned gorillas. In fact, the young gorillas ultimately showed stronger social bonds with the dominant male of the group and with other gorillas of the same age.
This increase in “affiliative interactions”, say the authors, may mimic the same dynamic seen in humans, where family and friends often step in to help care for children who have lost a parent.
Ape families are stronger together
Mountain gorilla social structures involve close-knit “family” groups, led by a silverback male who, in most cases, sires the majority of offspring. The group often contains multiple adult females, their offspring and sometimes other subordinate males.
Male gorillas have previously been observed caring for younger members of their social group. When a younger gorilla loses their mother, this caregiver role expands; dominant males were observed spending more time beside the orphaned young gorillas and more commonly engaging in grooming behavior with them. This increased care persisted even if the dominant male was not the genetic father of the orphan.
“These findings suggest that our capacity to care for other group and family members in times of need may be deeply rooted within our DNA and something we share with gorillas,” said Morrison.
“Just like us, gorillas live long lives, so it takes years for researchers to record the rare and fascinating behaviors that occur over a gorilla’s lifetime. Our dataset, one of the longest of any animal species, stretches back more than 50 years, helping us understand how much we share with one of our closest relatives as we work to protect them and their biodiverse habitat,” concluded Dr Tara Stoinski, CEO and chief scientist of the Dian Fossey Gorilla Fund and the study’s senior author.