According to the researchers, the swift, heroic actions of the capuchin group “clearly support the hypothesis that predation has been a strong selective force driving sociality in primates.” A tight social bond can be the difference between life and death for an individual within a group. And direct kinship is not required. In this case, the group’s alpha male risked his life to save the juvenile even though he was not actually related to the young monkey.
“The threat of constricting snakes may have been a particularly strong selective force in early primate evolution when primates were small bodied and, therefore, more susceptible to fall prey to constricting snakes,” the researchers conclude.
Cooperative rescue of a juvenile capuchin ( Cebus imitator ) from a Boa constrictor
The threat of predation by snakes is considered to have played a significant role in the evolution of primate sensory systems and behavior. However, we know relatively little about individual and group responses given the rarity of observed predation events. Here we report an observed (filmed) predation attempt by an adult Boa constrictor (~ 2 m) on a juvenile white-faced capuchin ( Cebus imitator ) in the Sector Santa Rosa of the Área de Conservación Guanacaste, Costa Rica. The snake caught the juvenile monkey on the ground during a terrestrial play session. When the victim screamed, the alpha male, alpha female, and another adult female ran to the scene, physically attacked the snake (with bites and hits), and pulled the victim to safety. Most group members participated in the vocal mobbing of the snake both during and after the attack. Based on the outcomes of this predation attempt and published reports of other B. constrictor attacks on primates, the coordinated efforts of ≥ 2 group members is needed for a successful rescue. This observation adds to our growing knowledge of cooperative group behavior and its importance in predator defense.