Muriquis feeding and resting. Photo from Primate Info Net.

The muriquis, or woolly spider monkeys live in the rain forest of Brazil. They are considered peaceful individuals but an intra-community lethal attack had left researchers to reconsider how peaceful these monkeys are and why such attack occurred.

The image of peaceful individuals mainly stemmed from the northern population. Leaves are abundant in the northern population, so these muriquis chew on leaves all day and males would patiently queue to mate with females. When food is abundant, animals tend to stay in the same place.

However, in the southern population, fruits tend to be more abundant. Generally, females need more caloric intake compared to males, so females from the southern population disperse from the group to find clumps of fruits unlike the northern population where everyone stays together to eat.

It is in the southern population that a gang of six male muriquis were observed attacking another male from the same group, brutally biting his face, body and genitals. The male died about an hour later.

A change in dietary habit might be the clue to why such assault happened, said lead researcher Mauricio Talebi of the Federal University of São Paulo-Diadema, Brazil. Social bonding also explains why a gang of males attacked another male. Due to lack of readily available mates, males may become frustrated, creating tension and aggression between individuals. Because muriqui males bond for life with male siblings and relatives, this facilitates gang attacks, said Filippo Aureli of Liverpool John Moores University, UK. This assault can be seen as aggression among non-kin males.

For more, read ‘Hippy’ monkey is a killer when starved of sex on NewScientist and Intra-community coalitionary lethal attack of an adult male southern muriqui (Brachyteles arachnoides) on Wiley Interscience.

Originally posted on Prancing Papio.