Chimpanzees: Hormone oxytocin likely to play key role in maintaining social relations with cooperation partners

Jan 23, 2013
The Sonso group in the Budongo Forest, Uganda: two male chimpanzees grooming each other, a very intimate behaviour based on trust. Credit: Liran Samuni

Animals which maintain cooperative relationships show gains in longevity and offspring survival. However, little is known about the cognitive or hormonal mechanisms involved in cooperation. Researchers of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have now found that cooperative relationships are facilitated by an endocrinological mechanism involving the hormone oxytocin, even when these are between non-kin. They collected urine samples of 33 chimpanzees from Budongo Forest, Uganda, and measured their urinary oxytocin levels after single episodes of a specific cooperative behaviour, mutual grooming. The result: Oxytocin levels were higher after grooming with cooperation partners compared with non-cooperation partners or after no grooming, regardless of genetic relatedness or sexual interest. This suggests that in chimpanzees oxytocin, which acts directly on neural reward and social memory systems, plays a key role maintaining social relations beyond genetic ties and in keeping track of social interactions with multiple individuals over time.

In non-human primates and other strong and enduring are typically seen between genetically related individuals but also, occasionally, between non-kin, same-sex individuals. Although such relationships are typically defined by high rates of cooperative behaviours, how they are maintained over time is still unclear. In humans and other social mammals the neuropeptide hormone oxytocin plays a central role in facilitating bonding between kin and mating partners. Catherine Crockford, Roman Wittig and colleagues of the Max Planck Institute for Evolutionary Anthropology have now analysed the role of this hormone in the between wild chimpanzees.

To this end the researchers observed social interactions – like mutual grooming – in a group of wild chimpanzees from Budongo Forest in Uganda and non-invasively collected urine samples of the 33 female and male adult group members on plastic bags or leaves. They determined the level of the hormone oxytocin before and shortly after the animals had been grooming with each other and found that were especially high in chimpanzees who had been grooming with a "bond partner",  a cooperation partner, irrespective of whether this bond partner happened to be their kin or not. On the other hand, the level of urinary oxytocin was much lower in chimpanzees who had been grooming with a "non-bond partner", with whom they did not share a cooperative relationship, or in animals who had not been grooming at all. Furthermore, the researchers found that the animal's sex or age, grooming duration and other factors did not have a significant influence on urinary oxytocin levels.

"Our results demonstrate that a rise in oxytocin was dependent upon the combined effects of social grooming with a bond partner", says Catherine Crockford of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. "Crucially, oxytocin levels were similarly high after grooming with non-kin and kin bond partners. This suggests that, in chimpanzees, oxytocin plays a key role in maintaining social relations beyond immediate genetic ties".

"This is the first study that measures the levels of the on wild animals in a non-invasive way", says Roman Wittig of the Institute for Evolutionary Anthropology. "We have developed a tool with which cross-species comparisons that link underlying physiology and behaviour can eventually be made of social mammals in their natural environment". In future field research this tool will be used to compare single behaviours – like other cooperative  or aggressive behaviours – by measuring how they differ from each other hormonally.

Explore further: Male monkey filmed caring for dying mate (w/ Video)

More information: C. Crockford, R.M. Wittig, K. Langergraber, T. Ziegler, K. Zuberbühler, T. Deschner. Urinary oxytocin and social bonding in related and unrelated wild chimpanzees
Proceedings of the Royal Society B, January 23, 2013.

Related Stories

Chimpanzees create social traditions

Aug 29, 2012

(Phys.org)—Researchers have revealed that chimpanzees are not only capable of learning from one another, but also use this social information to form and maintain local traditions. A research collaboration ...

Oxytocin: It's a mom and pop thing

Aug 20, 2010

The hormone oxytocin has come under intensive study in light of emerging evidence that its release contributes to the social bonding that occurs between lovers, friends, and colleagues. Oxytocin also plays an important role ...

Recommended for you

Male monkey filmed caring for dying mate (w/ Video)

Apr 18, 2014

(Phys.org) —The incident was captured by Dr Bruna Bezerra and colleagues in the Atlantic Forest in the Northeast of Brazil.  Dr Bezerra is a Research Associate at the University of Bristol and a Professor ...

Orchid named after UC Riverside researcher

Apr 17, 2014

One day about eight years ago, Katia Silvera, a postdoctoral scholar at the University of California, Riverside, and her father were on a field trip in a mountainous area in central Panama when they stumbled ...

In sex-reversed cave insects, females have the penises

Apr 17, 2014

Researchers reporting in the Cell Press journal Current Biology on April 17 have discovered little-known cave insects with rather novel sex lives. The Brazilian insects, which represent four distinct but re ...

Fear of the cuckoo mafia

Apr 17, 2014

If a restaurant owner fails to pay the protection money demanded of him, he can expect his premises to be trashed. Warnings like these are seldom required, however, as fear of the consequences is enough to ...

User comments : 0

More news stories

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...

Biologists help solve fungi mysteries

(Phys.org) —A new genetic analysis revealing the previously unknown biodiversity and distribution of thousands of fungi in North America might also reveal a previously underappreciated contributor to climate ...

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.