|The largest primate in the Western Hemisphere is the woolly spider monkey called
muriqui. It is one of the most endangered of all primates and it lives along the
Brazilian coast. There are only 300- 400 woolly spider monkeys left in the world.
Their near demise has resulted because of their forest habitat has been nearly
removed by loggers and those seeking farmland to grow food.
Studies of the woolly spider monkey have discovered that they have a unique social
system. In a study group of 26 individuals continuously observed over 14 months,
scientists found an "extraordinary degree" of cooperation and friendship among males.
Only the spider monkey and the chimpanzee exhibit comparable levels of "male
bonding. Even more striking are the low levels of aggression between male muriquis.
Unlike most other primates, indeed, most other vertebrates, male muriquis show no
overt competition over access to mates.
An important reason for this cooperative behavior appears to lie in family ties. Male
muriquis did not leave a study group, conducted by biologists, suggesting that they
mated with the same limited sample of females and, over the generations, had
become genetically related to one another.
Young females, on the other hand, may tend to leave the group into which they are
born; during scientific observations, two juvenile females immigrated into the study
group. Nevertheless, adult males and females travel together in the same group with
few signs of conflict, and no adverse effects of inbreeding are currently evident.
Cohesive groups, she notes, are better able to compete with other bands of muriqui
for the relatively rare fruit species that they prefer to eat.
The pattern of male bonding and female dispersal, a reversal of what is usually
observed in primate species, will need to be confirmed in other surviving muriqui
groups. But knowledge of their strong social relationships will aid efforts to establish
captive groups that can reproduce successfully and prevent their extinction.
Corwin, J. 100 Heartbeats: The Race to Save Earth's Most Endangered Species.
Strier, B. Faces in the Forest: The Endangered Muriqui Monkeys of Brazil. 1999.