Réponses des populations de reptiles à l’éradication du Rat noir (Rattus rattus) sur l’île de Bagaud (parc national de Port-Cros, Var, France)

Abstract

Responses of reptile populations to the eradication of the Roof Rat (Rattus rattus) on Bagaud Island (Port-Cros National Park, Var, France). — An eradication of two invasive taxa, the Roof Rat (Rattus rattus) and Ice plants (Carpobrotus spp.), was undertaken in 2011 and 2012 on the protected nature reserve of Bagaud island, located in Port-Cros national Park (south-eastern France). R. rattus eradication was successful while Carpobrotus spp. eradication is still in progress. To assess the effects of R. rattus eradication on island reptile populations (Montpellier Snake Malpolon monspessulanus, European Leaf-toed Gecko Euleptes europaea, Common Wall Lizard Podarcis muralis), a pre-eradication monitoring was conducted in 2010 and 2011, and a post-eradication monitoring in 2013 and 2014. Census was performed with three semi-quantitative methods : (1) three transects of 80 m long and 2 m wide ; (2) two quadrats 1225 m² ; (3) five rocky microsites, habitats for E. europaea. Very few individuals of M. monspessulanus were observed. Significant results were obtained only for E. europaea : after eradication, the number of observed juveniles increased and all observed individuals, independently of their age groups, were more outside shelters than inside. These results can be explained by the loss of avoidance behaviour that E. europaea displayed when in presence of R. rattus, and by lower predation pressure, given that both species are nocturnal. The elapsed time since eradication of R. rattus is quite short and some species have not necessarily visibly responded demographically. Additional monitoring in the coming years will provide further insights.