Assessing occupancy and activity of two invasive carnivores in two Caribbean islands: implications for insular ecosystems

The introduction of exotic species is one of the major causes of the decline of global biodiversity. Tropical insular ecosystems, including many biodiversity hotspots, are particularly threatened by biological invasions. Two wild carnivores have been introduced in the Caribbean, the northern raccoon Procyon lotor and the small Indian mongoose Urva auropunctata. Understanding the spatial distribution and activity patterns of both species is crucial for conservation purposes. Here we used camera trap data to model single-season occupancy and detection of these two species on two Caribbean islands, Guadeloupe and Martinique. Our survey highlighted the broad distribution of both species on these islands, with the exception of the northern raccoon population in Martinique which appears very limited. Moreover, spatio-temporal co-occurrence with other bird and mammal species revealed that the northern raccoon and the small Indian mongoose face few or no competitors. Finally, our models show that the occupancy of both species was not influenced by any variable tested (i.e. elevation, precipitation, temperature and land cover) and that the probability to detect small Indian mongooses was influenced by land cover and camera model. These results highlight the potential of both the northern raccoon and the small Indian mongoose to have a significant impact on the native ecosystems in these hotspots of biodiversity and demonstrate the necessity to develop conservation actions towards control and limitation of these invasive carnivores.