Barbary macaques form male bonds, study reveals

Researchers studying wild Barbary macaque males living in their natural habitat in the Middle Atlas Mountains in Morocco discovered that keeping a few close male associates buffered against day-to-day stressors, decreasing the levels of the stress hormone glucocorticoid.

Elevated levels of the hormone over prolonged periods of time makes the monkeys more susceptible to illness and mortality. Such 'friendships' were previously only thought to be formed between females, making the discovery of these friendly relationships significant, researchers said.

The study, which was carried out by Germany's University of Göttingen and the German Primate Center, the University of Lincoln, UK, and the University of South Africa, examined the 'social buffering hypothesis' which has also been proven to improve health in humans.

Co-author Dr Bonaventura Majolo, a behavioural ecologist based in the School of Psychology at the University of Lincoln, said: "Although male sociality has received little to no attention from scientists until recently, strong social bonds between males can yield a number of benefits, including increased dominance rank, and mating and paternity success.

This study shows that changes in everyday stressors such as the amount of aggression received or cold weather can cause long-term elevated glucocorticoid levels in wild male Barbary macaques, but keeping a few close male associates will avoid that.

We already know that female primates which lack these strong bonds show increased mortality and reduced offspring survival, whereas those who established and maintain strong bonds cope better with stressful situations and live a longer life.

Our findings show that males also benefit from maintaining strong bonds, and suggest that the ways in which social mammals affiliate, cooperate, and compete among each other is not fundamentally different in gregarious males and females."

Links have previously been made between social bonds in humans and positive mental and physical health, and these new findings in primates help support the view that the fundamental 'blocks' of social behaviour are the same in humans and other social mammals.

The study is published in the US academic journal Proceedings of the National Academy of Sciences (PNAS).