Primates prefer to fight with friends at their side
Cheyenne MacDonald / Mark Prigg
For chimpanzees, a 'bromance' is an important social bond that can lower stress and lead to a longer life, researchers say.
The bonds between male chimpanzees have been found to work as a buffer in social settings, making confrontations less stressful for a chimp who fights alongside a close partner.
Researchers say that these friendships benefit both genders, and mirror the effects of close relationships among human social circles.
For chimpanzees, a 'bromance' is an important social bond that can lower stress and lead to a longer life, researchers say. The bonds between male chimpanzees have been found to work as a buffer in social settings, making confrontations less stressful for a chimp who fights alongside a close partner
Adult male chimps can be extremely violent, but that doesn't mean they don't cozy up to their best friends.
In a chimp bromance, closely bonded males will engage in cooperative behaviour, according to New Scientist, sharing food and even grooming vulnerable areas, including genitalia.
And, chimpanzees aren't alone in this – other primates, including macaques and baboons are also known to form close friendships.
These friendships have been found to play an important role in the aggressive interactions of warring chimps.
'Chimpanzees are highly territorial and encounters with neighbouring groups tend to be very hostile and can be deadly,' said Catherine Crockford of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, at the Ethological Society annual meeting in Göttingen, New Scientist reports.
By tracking wild chimpanzees in Uganda and the Ivory Coast, the researchers found that after a fight, a chimp would be less stressed if a grooming partner had been present to back him up.
To determine this, the researchers analysed glucocorticoid stress hormone levels in chimp's urine after a fight, according to New Scientist.
Stress hormones in chimps are released from the adrenal glands due to the interactions of the 'hypothalamic-pituitary-adrenal (HPA) axis.
In cases of trauma or chronic stress, these interactions can veer off course.
'Dysregulation of the HPA axis can impair reproductive and immune function, disturb moods, cognition and social relationships, leading to poor health, social isolation, and early death,' Crockford said at the conference, New Scientist reports.
Similar research on Barbary macaques by a team from the University of Göttingen found that the primates would have lowered glucocorticoid levels during a fight or cold temperatures when they have strong social bonds.
Chimpanzees munch on leek at Tokyo's Tama Zoo. Adult male chimps can be extremely violent, but that doesn't mean they don't cozy up to their best friends. Closely bonded males will engage in cooperative behaviour, researchers say, sharing food and even grooming vulnerable areas, including genitalia
The studies suggest that the close friendships help lower the stress associated with certain interactions, like an aggressive encounter.
Friendship may occur as an evolutionary result of mother-infant bonding, according to Crockford.
The research reveals an increase in oxytocin among chimps in bonded pairs, and this hormone is known to mediate the mother-offspring bond, and that of sexual partners.
Friendship may occur as an evolutionary result of mother-infant bonding. The research reveals an increase in oxytocin among chimps in bonded pairs, and this hormone is known to mediate the mother-offspring bond, and that of sexual partners. Like in humans, chimp friendships are based on trust
Having close friends can help to strengthen alliances within a large group.
Like in humans, chimp friendships are based on trust, a recent study explains.
The report, published in the journal Current Biology, examined the interactions of chimpanzees at Sweetwaters Sanctuary in Kenya over five months.
Scientists identified each chimp's closest 'friend' by those who ate together and groomed each other and one of their 'non-friends.'
The interactions between the chimps showed 'much greater trust between friends than non-friends,' according to the study.
'Chimpanzees were significantly more likely to voluntarily place resources at the disposal of a partner, and thus to choose a risky but potentially high-payoff option, when they interacted with a friend as compared to a non-friend,' the researchers said.
Jan Engelmann, one of the scientists behind the study, said, 'Human friendships do not represent an anomaly in the animal kingdom.
'Other animals, such as chimpanzees, form close and long-term emotional bonds with select individuals.
'These animal friendships show important parallels with close relationships in humans.
'One shared characteristic is the tendency to selectively trust friends in costly situations.'
The scientists plan to investigate more possible similar characteristics between humans and chimpanzees, including whether chimps are more likely to offer help to their friends.