Another scenario in which the entire troop behaves cooperatively is when they cross paths with a potential predator. Several weeks ago we encountered a Boa constrictor, about 4' in length, crossing the dirt road near the Finca. We bagged it and brought it back to the house for some photos, and it just so happened that the monkeys were in the yard (robbing the bananas from the bird feeder, as they do regularly, much to our continual frustration) when we extracted the Boa from the bag. Instantly it was spotted by one of the young females of the group, who began sounding the alarm (sort of an outraged- and offended-sounding "UGH!"). Within seconds the entire troop had congregated on the roof nearby to inspect the danger, and to issue alarm calls of their own.
Interestingly, younger Capuchins will sound alarm calls much more frequently, and often inappropriately - they may scold harmless snakes, snake sheddings, and non-predatory birds, for example. But they learn to discriminate between the harmless and the potentially threatening creatures as they get older and gain more experience. An interesting hypothesis regarding snake-mobbing is that when older, more experienced adults sound the alarm to alert the group of a snake of the dangerous variety, they are helping teach the younger, inexperienced monkeys to differentiate between them and the harmless variety.
|Adult male with a younger female reacting to a Boa constrictor|
After about twenty minutes, the monkeys seemed convinced that the snake's presence was sufficiently announced, and dispersed to continue their routine vandalizing of the yard in search of food. We photographed our boa and released him, well out of sight of the monkeys.