Gorillas adjust aggression based on personal needs and group social dynamics

Non -human animals can adapt the intensity and management of aggression to meet their individual needs and their social contexts, according to a recent study.

The study, published in the form of revised preparation in ElifeWith the revised version appearing on July 23, is described by publishers as an important research which uses long -term behavioral observations to understand the factors that influence female assault on the social groups of the gorilla.

They say that the evidence supporting the assertions are convincing because they include new methods of aggression evaluating and considers other potential factors. The work will be of interest to biologists and environmentalists working on the social interactions of animals and on broader human societal relations.

Animals that live in groups often compete for access to resources such as food and partners, forming hierarchies that determine the priority of access. Group individuals must choose strategically with who to compete, at different calendar points, to maximize the gain of resources and status while minimizing costs, such as energy expenditure and risks.

“Aggression – a competition proxy – tends to increase when the resources are limited and are generally directed towards individuals of lower rank, but can vary towards group comrades of different ranks, and the variation is observed even within species”, explains the main author Nikos Smit, a postdoctoral scientist of the Max Planck Institute for Evolutionary Anthropology, German and University of Turku, final.

“In this study, we have tested the hypothesis that this variation occurs because of different conditions that individual animals experience, and that the needs of an individual and the social environment shape their aggression towards different individuals of classification, as provided for by the theory of risk taking.”

To test this hypothesis, the authors used behavioral observations of 25 years among a total of 31 adult female gorillas of five groups of wild gorillas – a group of Western gorillas in Gabon, Central Africa and four groups of mountain gorillas in Uganda, East Africa. The trained observers have recorded behaviors used to deduce the hierarchies of female gorillas (like the decided avoidance – moving away from an individual who approached) and attributed to each female gorilla a rank in the hierarchy.

Observers also recorded aggressive interactions between adult women and have awarded a score to each of these interactions to quantify the direction of the aggression, and in particular if the aggression was directed towards more or less powerful individuals, depending on the relationship of aggressor.

After having analyzed 6,871 aggressive interactions, most of the assault was directed by the individual of higher rank to low -rank individuals, in accordance with the hypothesis that high -ranking individuals generally use an aggression to strengthen their status. The percentage of aggressive interactions of lower to higher individuals was lower, at 42%, but higher than that observed in previous and higher studies than in many other animals.

Compared to other women, those pregnant and in lactation led the assault towards more powerful group comrades, which reflects their increased energy needs. However, despite the potentially higher energy needs of breastfeeding females, pregnant women led the assault towards more powerful group comrades compared to them. The authors suggest that this could be due to the fact that breastfeeding women are less likely to take the risk of assault towards higher group comrades because they must protect their dependent infants.

The female gorillas have directed more assault to more powerful and higher women when there were more men in the group, which suggests that male protection offers an environment in which females will take greater risks. On the other hand, female gorillas directed more assault to women of lower and less powerful row when there were more women in the group, which suggests that women prefer to target lower opponents when they have such an option. Together, these results confirm that gorillas can adapt the assault to their social context.

“Overall, our results confirm that the circumstantial needs of an individual and his social environment can influence individual decisions to adopt more risky behavior such as the assault towards more powerful group comrades,” concludes Martha Robbins, group leader at the Max Planck Institute for the evolutionary anthropology.