Isolation from mammalian predators differentially affects two congeners [Isolement des prédateurs mammaliens affecte différentiellement deux congénères].

Résumé

Evolutionary isolation from predators can profoundly influence the morphology, physiology, and behavior of prey, but little is known about how species respond to the loss of only some of their predators. We studied antipredator behavior of a wallaby and a kangaroo on an island, where they have been isolated from mammalian predators for several thousand years but remain vulnerable to aerial predators, and on the mainland, where both species have been exposed continuously to mammalian and avian predators. At both locations, wallabies modified the amount of time they allocated to vigilance and foraging in response to group size, whereas kangaroos did so only at the higher-risk mainland site. Both species modified overall time budgets and space use patterns, but wallabies were closer to cover at the mainland site, while kangaroos were, on average, farther from cover. The presence of a single predator may affect the way a species responds to the loss of other predators by maintaining certain antipredator behaviors. Such an effect of the ghost of predators past may be expected as long as species encounter some predators.