Orphaned infant chimpanzees will be adopted by older brothers and sisters or other members of their community, new research by the University of St Andrews has shown.
Observations of a chimpanzee group in Uganda revealed that humans and the primates have something in common when it comes to dealing with infants.
University of St Andrews psychologists Dr Catherine Hobaiter and Professor Klaus Zuberbühler discovered different types of adoption, and that adoption itself significantly increased an orphaned chimpanzees’ chances of survival.
The research shows that where no mother is present, maternal siblings, even those that are very young, will adopt their younger brothers and sisters, becoming families of young orphans.
Where no maternal siblings are present, unrelated adults will adopt an orphan in their community but only once a social bond has developed.
The adoptive ‘parents’ were seen to carry the young infants, wait for them while travelling, share food with them, and even stick up for them during fights.
Dr Hobaiter explains: “It may sound obvious – that adoption is beneficial – but in previous work in West Africa the overall chimpanzee survival rates were so low that it was hard to demonstrate this.
“By looking at data across several long-term sites, including our own in Uganda, we were able to show that being adopted, even by a juvenile brother or sister, increased a young orphan’s chance of survival.”
It appears it is the social bonds between individuals, rather than just biological relatedness, that are key to the adoption process.
Wild chimpanzees remain with their mothers until maturity, but spend very little time with their fathers. As a result, while they are equally related to their siblings through either their mother or father, they only develop strong social bonds with their maternal brothers and sisters, and it is only between these maternal siblings that adoptions occur.