Pacific Black Face

The muriquis live in social groups of up to 35 individuals, including several adult males and females, and there are apparently large variability in social structure and intragroup spacing in different populations. It is believed that among spider monkeys there is a very fluid social organization, where males and females have overlapping home ranges, which makes it difficult to characterize the groups and subgroups that may vary greatly in their composition.

Some studies have shown that a small percentage of the diurnal time is spent with social interactions. Despite this, some categories of social behavior, especially the hugs, notable for its intensity. Hugs often occur when they are observed meetings between spider monkeys, spider monkeys are or when animals of other species, also occur during the troop meeting or as a ritualized form of greeting between individuals who apparently recognize, but were separated for some time, reassuring mutual solidarity. Hugs are also characterized by high frequency at which the members mutually begin by showing that happen to individuals resume their brotherly relations.

Yet despite the little time devoted to social interactions, Muriquis adults, unlike other species of primates live in social groups composed of individuals of both sexes, rarely engage in aggressive interactions, and is considered an extreme among primates for their low aggressiveness.

The spider monkey has a great tolerance among individuals, and often forage, travel and sleep in close proximity, without being observed evidence of direct competition. This is particularly interesting among the adult males of the same group that, while they remain close to each other do not engage in direct competition, including by females capable of reproduction.

The reproductive system can be characterized as promiscuous. Adult females in estrus (the female during copulation emits a vocalization and shows a characteristic facial expression.) Are receptive to all adult males in the group, and may mate with several males in a short time without monopoly or attempt to interrupt copulation.

This behavior different from the old world primates, showing a particular behavioral strategy, with a low rate of aggression and sexual behavior differently where a female can be fertilized by several males. They are considered the most peaceful primate, and is critically endangered.

But because these primates are so different from others that they had evolutionary advantage for this behavior is fixed, there are some theories that attempt to clarify this question:

• The low calorie content of their basically vegetarian diet would imply an energy restriction for individuals to participate in social interactions particularly aggressive?
• Their varied diet and how food items are distributed, can enable individuals to avoid direct competition feeding on alternative sources?
• Due to its size and its need to distribute your weight, all its members are often used including the tail, to engage in a fierce dispute could lead to a fall that an animal as heavy as the spider monkey could cause serious injury or even death?

Among the males two theories can be highlighted:

• High degree of consanguinity, and relatives they would not need competition for females.
• There is also the possibility of direct competition for access to females has been replaced by sperm competition. This hypothesis is based on the size of the scrotum of adult males, and the amount of sperm that drips from the vaginal cavity of females after copulation.
• Yet other studies are underway and many others will be designed to address this issue. It is important to note that studies in different populations of spider monkeys, either in continuous forest fragments or portions of the Atlantic provide new elements to the knowledge of the species, which are working and how the different factors for this characteristic low aggression to occur.