Socioecology Case

Primate Socioecology studies the relationship between environmental variables and primate's social behavior. Richard Wrangham was the first to propose that intragroup feeding was a key link in the evolution of primate grouping patterns. His current model of primate socioecology focuses on feeding ecology and the competition that primates face within and outside their groups. The abundance and distribution of food influences feeding competition within and outside of the group, which in turn determines the type of social relationships among females which also influence the distribution of males and therefore determines the social system.

Primates live in groups because of its advantages. Two theories for their sociality are the improved competition for resources with other groups and an increase defense from predators. Wrangham suggested that primates tend to stay in groups because groups tend to be more successful at defending food resources than if they lived alone (Fuentes, 2011). Van Schaik argued that predation pressure added complexity to the feeding competition. He concluded that small groups are a result of predation risks while larger groups are influenced by feeding competition. Variations in predation risk and the abundance and distribution of food influence female relationships resulting in four main social systems (Fuentes, 2011).

In a "dispersal-egalitarian" system predation risks are high, food is dispersed and the population density is low. Scramble competition occur within the group because the food is not defensible causing alliance and dominance hierarchies to not be important. In such systems we tend to see an increase in females dispersing at maturity because there is no competition for food. In a

"resident-egalitarian" system where predation risk are high, food is dispersed with a high population density we see a high between-group contest competition because of the larger population but a low in-group completion because the food is dispersed. Female dominance is important in such a case which causes female philopatry and nepotism between kin. A third system known as the "resident-nepotistic" predation risk is still high, population density is low and but the food resources are clumped together making it defensible. Low between-group contest competition and high within-group contest competition can be observed causing coalition formation and nepotism between females resulting in female dominance hierarchy and female philopatry. The last system, "resident-nepotistic-tolerant" results from low predation risk, high population density and clumped food resources. As a result we observe both in-group and between-group contest competition causing strong female dominance and rare female dispersal from the group.

"These parameters of ecological constraints on food then determine the type of groups that females form and types of relationship between females" (Fuentes, 2011). Females gain dominance in how they compete for food resources within their group and to be a successful rank member they often cooperate in its defense with kin. Nepotistic support enhances the stability of dominance because of the reinforced alliance causing female philopatry. On the other hand if food is not defensible, female bonds will be weak causing them to disperse from the group. In the socioecological model the presence of males are determined by the distribution

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