Native reptiles alter their foraging in the presence of the olfactory cues of invasive mammalian predators

Abstract

Invasive mammalian predators are linked to terrestrial vertebrate extinctions worldwide. Prey naïveté may explain the large impact invasive predators have on native prey; prey may fail to detect and react appropriately to the cues of novel predators, which results in high levels of depredation. In Australia, the feral cat ( Felis catus ) and the red fox ( Vulpes vulpes ) are implicated in more than 30 animal extinctions and the naïveté of native prey is often used to explain this high extinction rate. Reptiles are one group of animals that are heavily preyed upon by F. catus and V. vulpes . However, very few studies have examined whether reptiles are naive to their cues. In this study, we examine the ability of two native reptile species ( Morethia boulengeri and Christinus marmoratus ) to detect and distinguish between the chemical cues of two invasive predators ( V. vulpes and F. catus ) and three native predators (spotted-tailed quoll, Dasyurus maculatus; dingo, Canis lupus dingo ; eastern brown snake, Pseudonaja textilis ), as well as two non-predator controls (eastern grey kangaroo, Macropus giganteus and water). We conducted experiments to quantify the effects of predator scents on lizard foraging (the amount of food eaten) during 1 h trials within Y-maze arenas. We found both study species reduced the amount they consumed when exposed to predator scents—both native and invasive—indicating that these species are not naive to invasive predators. An evolved generalized predator-recognition system, rapid evolution or learned behaviour could each explain the lack of naïveté in some native Australian reptiles towards invasive predators.