A critical evaluation of the influence of predators on primates: effects on group travel

摘要: A troop of Costa Rican squirrel monkeys (Saimiri oerstedii) is in a patch of early second-growth forest, eating fruits of Cecropia (Moraceae) and Piper (Piperaceae) and the occasional caterpillar. The sudden onset of raucous and frenetic alarm cal! s disturbs the tranquil scene, yanking the observer's attention to a voracious-looking crested eagle (Morphnus guianensis) perched 4 meters above the ground in what had been the center ofthe troop's dispersion. Adult females and immatures immediately coalesce into a writhing baU of more than forty squirrel monkeys within the protective confines of a dense vine tangle. Meanwhile. twenty foolishly valiant adult and subadult males are mobbing the raptor. literaUy throwing themselves at the bird. The squirrel monkeys slide off the raptor and thump to the ground below without ruffling a feather, much less the predator's composure. After several minutes of barrage by the small-bodied squirrel monkeys, the crested eagle spreads its wings and launches into a flight that skims the shrubby growth. It makes