Ship rats and island reptiles: patterns of co-existence in the Mediterranean

BACKGROUND: The western Mediterranean archipelagos have a rich endemic fauna, which includes five species of reptiles. Most of these archipelagos were colonized since early historic times by anthropochoric fauna, such as ship rats (Rattus rattus). Here, I evaluated the influence of ship rats on the occurrence of island reptiles, including non-endemic species. METHODOLOGY: I analysed a presence-absence database encompassing 159 islands (Balearic Islands, Provence Islands, Corso-Sardinian Islands, Tuscan Archipelago, and Galite) using Bayesian-regularized logistic regression. RESULTS: The analysis indicated that ship rats do not influence the occurrence of endemic island reptiles, even on small islands. Moreover, Rattus rattus co-occurred positively with two species of non-endemic reptiles, including a nocturnal gecko, a guild considered particularly vulnerable to predation by rats. Overall, the analyses showed a very different pattern than that documented in other regions of the globe, possibly attributable to a long history of coexistence.