The secret lives of squirrel monkeys: Social behavior takes surprising turns among these tiny primates

Abstract

on't mess with Pacino. He brawls D hard and dirty, and he stoically takes his licks. Constant no-holdsbarred battles have left wicked scars on his mouth and nose. Still, he looks good compared with the guys he regularly thrashes. Their injuries include torn ears, permanent limps, scarred hands incapable of grasping, and missing tail segments. Pacino is the alpha male-top dog, so to speak-in a troop of South American squirrel monkeys. As the undisputed champ of daily tooth-and-claw clashes, Pacino reigns over about a dozen adult males who operate as a loose-knit gang when not disfiguring each other. Pacino and his male underlings dole out plenty of abuse to the opposite sex as well. Hostile acts range from grabbing fruit out of females' mouths to pinning females down to force them to copulate. Simply put, these fuzzy little guys, weighing in at around 1.5 pounds, are pigs. Yet the long-suffering females show no signs of organizing efforts to protect their food or to fend off Pacino and his nasty boys. Instead, each adult female largely sticks to raising her kids and searching alone for fruit and insects. So goes the unpleasant lives of standard-issue squirrel monkeys, an observer might conclude. Not exactly. The social arrangements of Pacino and his terrorized troop, who live in the country of Suriname, north of Brazil, are as different from those of Costa Rican squirrel monkeys as a street gang's code of conduct is from Amish etiquette. Moreover, Peruvian squirrel monkeys take another path altogether, emphasizing what some might call girl power. Among the Costa Rican primates, neither sex tries to push the other around or to control food supplies, and fighting almost never occurs. In Peru, however, close-knit groups of females rule. Males keep their distance as females peruse the best foraging spots; sexual activity takes place only when a female signals her readiness to a suitor of her choice. Either of these social scenes would repel Pacino, whom researchers in the field named after actor Al Pacino, perennial movie tough guy. During the past 2 years, a team led by anthropologist Sue Boinski of the University of Florida in Gainesville has for the first time documented the uneven battle of the sexes in the Surinamese squirrel monkey population. Pacino the squirrel monkey, though he acts like his namesake's character in Scarface, plays in a larger drama that might be called The Three Faces of Saimiri. Scientists place all squirrel monkeys in the