Cooperation with friends helped monkeys to reduce stress

The levels of the hormone cortisol in individuals macaque the crab (Macaca fascicularis) is reduced after they perform the task of getting treats along with relative — but only if they are close relatives. It found European zoologists, who conducted an experiment involving 14 monkeys: they had to get a treat from the tray by pulling on a rope at the same time with the kindred. The study indicates the involvement of glucocorticoids in the regulation of behavior in cooperation, and that cooperation appears to be, can reduce stress. Article published in Royal Society Open Science.

For social animals it is very important to cooperation: it helps to protect the territory find food and also to educate the offspring and to attract partners for his appearance. While cooperation sometimes requires much more resources than a single work; to cooperate may require more cognitive cost and regulation of behavior, in which, among other things, involve the regulation of the hormonal system of the body. For example, glucocorticoids ensure the success of the societies of social animals, but their level also depends on the level of aggression in the group.

It is clear that the involvement of glucocorticoids in cooperation should provide individuals some benefit — for example, to reduce the level of stress. Find out if it’s a monkey, the crab, decided scientists under the leadership of Martina Stocker (Stocker Martina) from the University of Vienna: in their study involved 14 macaques (five of them males) living in captivity.

Within six months of observations, researchers evaluated the social ties within the group to determine the hierarchy and mark the close species for each animal. After that, the scientists conducted an experiment using the paradigm of cooperative rope pulling, which is often used for the study of animal societies: while performing this job treats you need to get off of the pallet and push it to herself only by pulling the ropes simultaneously. Before performing the task the animals broke into pairs (as close to the individual and individuals who do not spend a lot of time together), and in the control condition, the monkey pulled the pan (but a different, single) yourself either alone, or with the audience near relatives, which, however, does not help him.

To run the job and after the scientists collected saliva samples of macaques to assess the levels of the hormone cortisol. Researchers found that cortisol levels in macaques fell after they performed the task of getting treats with a partner. Interestingly, the level of cortisol did not affect success when performing a task, and it decreased only in case, if partner macaques was close individual. In this case the animals have to perform a task together: in the case where the relatives just sat there, the level of cortisol in macaques has not changed.

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