Navigating new threats: Prey naïveté in native mammals.

Invasive predators pose a substantial threat to global biodiversity. Native prey species frequently exhibit naïveté to the cues of invasive predators, and this phenomenon may contribute to the disproportionate impact of invasive predators on prey populations. However, not all species exhibit naïveté, which has led to the generation of many hypotheses to explain patterns in prey responses. These hypotheses primarily fall into two categories: system-centric hypotheses related to biogeographic isolation (BIH) and species-centric hypotheses, like the archetype similarity hypothesis (ASH). We tested the predictions of these hypotheses by assessing the response of the common raccoon (Procyon lotor) and hispid cotton rat (Sigmodon hispidus), two native mammal species with divergent snake predation histories, to the cues of the invasive Burmese python (Python bivittatus) in the Florida Everglades (USA). Using giving-up densities (GUDs), we assessed the responses of both cotton rats and raccoons to life-size replicas of Burmese pythons and two North American predators-eastern diamondback rattlesnakes (Crotalus adamanteus) and coyotes (Canis latrans). Although cotton rats increased their GUD in the presence of all three predators relative to the novel-object control, raccoons only increased their GUD in coyote treatments. These results align with the predictions of the ASH but not the BIH, and mirror observed patterns of population declines in invaded areas of the Florida Everglades. More broadly, our findings suggest that naïveté may contribute to the vulnerability of some species to invasive predators even in large continental systems.