Predators reveal who your friends are

Crested macaques react faster if threatened by predators when a close friend calls for help. The research, published in Proceedings of the Royal Society B today, represents the first time the role of friendship has been investigated in the context of predator defense.

Primatologists from the University of Portsmouth found that when a group of crested macaques are attacked by a python, their alarm calls are more likely to elicit a response from friends.

Lead researcher Jerome Micheletta said: “Strong social bonds are crucial for humans’ health and well-being but friendship is not uniquely human. Similar bonds can be found in a wide range of animals from mice to monkeys, and together with dominance and kinship, friendship is a crucial feature of animal societies.

“We knew friendships were important among crested macaques but until now we didn't know whether it played a role during encounters with predators.

“We found that friendship influences the way individuals respond to alarm calls given in a potentially deadly situation.”

The scientists studied female crested macaques, monkeys known for their open, tolerant society.

The species have three main predators – dogs, pythons and humans. The presence of any will cause macaques to make an alarm call, but in the case of a python sighting, the alarm call is different – it is a recruitment call to other monkeys to join in a counter-attack by mobbing the python.

Jerome said: “This is where friendship has such an important role to play – mobbing poses a significant risk on those taking part and its success as a tactic depends on coordination and cooperation.”

Researchers used a mock-python – a life-size picture mounted on a metal handle – and taped the alarm call each macaque made. They played these back among groups of macaques and measured the response time of each individual in the group. They found that friends of the alarm-caller looked for longer towards the sound of the alarm call.

Co-author Dr Bridget Waller said “Strong social bonds could improve the coordination and efficiency of defence against predators and therefore increase the chances of survival of the individuals.

“You could say the costs of losing a friend outweigh the risk of joining in dangerous mobbing behaviour.”

Scientists don’t yet know if friendship evolved in direct response to threats from predators or whether it evolved for other reasons, for example, to help avoid the stress of living in large, complex groups.

The research was conducted in the wild, in the Tangkoko Nature Reserve, in the Macaca Nigra Project field site.