Assessing habitat preference of invasive minks (Neovison vison) using trap-cameras in Navarino Island, Chile

Background/Question/Methods

Invasive species are a significant component of global change, affecting native species, communities and ecosystems around the world. Among the most vulnerable are islands, where the introduction and establishment of mammalian predators are considered a major threat to native species. Here we report on a study conducted in Navarino Island, within the pristine wilderness of the Cape Horn Biosphere Reserve, Chile. American minks (Neovison vison) arrived to the island in 2001 and since then colonized the entire territory. Because minks are sub-aquatic, previous research has focused on coastal and riverine habitats; however, there is a gap of information on inland habitats. In this study, we aimed to investigate habitat preferences of invasive minks. We examined mink presence during February and March of 2013 by setting up 60 fish-baited trap-camera stations, operating for 16 days and spaced out 500m from each other. At each camera station, we measured altitude, canopy cover, vegetation density at ground level, macro-habitat type (mature forest, secondary forest, or shrub and grasses), and distance to coast and beaver dams. We fitted generalized linear models with negative binomial distribution to relate mink detections with habitat characteristics.

Results/Conclusions

We detected mink presence in 46% of camera stations. We obtained five best-supported models determined by Akaike’s information criteria corrected for small samples (ΔAIC_c <2).  Competitive models included the variables: vegetation density at ground level, type of macro-habitat, and distance to beaver dams. The other variables did not seem to be affecting mink detections. On the basis of model-averaged coefficients, only shrub and grasses habitat presented a significant negative effect on mink detections. Our results suggest that minks did not prefer any particular habitat characteristic that we evaluated. However, they seemed to be avoiding open areas dominated by grasses and shrubs compared with forest habitat. Future research is needed to better understand habitat selection. This is the first time that the use of forests by mink was recorded in the area. Given that birds and small mammals represent a significant portion of mink’s diet in Navarino Island and that fresh-water food is scarce, we believe that minks have expanded their niche moving away from water sources to hunt in the forest. This may have a significant impact on native bird species that evolved without mammalian predators on this island. We plan to evaluate this hypothesis in the future.