2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
The level of the hormone cortisol in cynomolgus monkeys (Macaca fascicularis) decreases after they complete the task of receiving a treat with a relative - but only if they are close to a relative. This was found out by European zoologists, who conducted an experiment with the participation of 14 macaques: they had to get the treat from the pallet by pulling the string at the same time as the relative. Research indicates that glucocorticoids are involved in the regulation of cooperative behavior, and that cooperation appears to be able to reduce stress. Article published in Royal Society Open Science.
Cooperation is very important for social animals: it helps to protect the territory, find food, as well as raise offspring and attract partners for its appearance. At the same time, collaboration sometimes requires much more resources than single work; for cooperation, more cognitive costs and regulation of behavior may be required, which, among other things, involve the regulation of the body's hormonal system. For example, glucocorticoids ensure the success of the cooperation of social animals, and the level of aggression in the group also depends on their level.
It is clear that the involvement of glucocorticoids in cooperation should provide certain benefits to individual individuals - for example, reduce stress levels. To find out whether this is so in the cynomolgus monkey, scientists led by Martina Stocker from the University of Vienna decided: 14 monkeys (five of them are males) living in captivity took part in their study.
Over the course of a month and a half of observations, scientists assessed social ties within the group to determine the hierarchy and mark the closest individuals for each animal. After that, scientists conducted an experiment using the paradigm of joint rope pulling, which is often used to study the cooperation of animals: when performing such a task, the treat must be removed from the pallet, and you can only pull it closer to you by pulling the ropes at the same time. Before completing the task, the animals were divided into pairs (both close individuals and individuals who do not spend much time together), and in the control condition, the macaque pulled on the pallet (but already another, single) independently, either alone or with a relative present nearby, which, however, did not help.
Before and after the assignment, scientists collected saliva samples from macaques to assess the level of the hormone cortisol. Scientists found that cortisol levels in monkeys dropped after they completed a meal task with a partner. Interestingly, the level of cortisol did not affect the success of the task, and it decreased only if the macaque's partner was a close individual. At the same time, the animals had to perform the task together: in the case when the relative was just sitting nearby, the cortisol level in the macaque did not change.
Post-assignment cortisol dependence for weak and strong social bonds between macaques
Scientists concluded that cooperation among this monkey species favorably affects cortisol levels, thereby reducing stress - this, in turn, confirms the involvement of glucocorticoids in the process of cooperation and the formation of strong bonds. The authors of the work noted that in the future it is also necessary to clarify how the regulation of cortisol is influenced by another hormone involved in social interaction, oxytocin.
Bottlenose dolphins, in particular, are famous for their cooperation, and this cooperation is manifested in different habitats. So, bottlenose dolphins can help each other to pull the strings to get toys, and in their natural habitat they sing a duet in order to attract females and then not fight for them.
