Invasion success of the large hairy armadillo (Chaetophractus villosus) in a sub-antarctic insular ecosystem (Isla Grande, Tierra del Fuego, Argentina)

Abstract

The large hairy armadillo (Chaetophractus villosus) was introduced to the Isla Grande of Tierra del Fuego almost 35 years ago. Previous studies described the armadillo’s distribution relative to heated oil pipelines. The present study updates this distribution, and evaluates associations with additional environmental variables to better explain the dispersion process and to propose areas for the control/eradication of this invasive species. We conducted 52 random transects looking for indirect evidence of the presence of C. villosus such as burrows and “foraging pits”. We looked for associations between the presence/habitat use of armadillos with local environmental characteristics and landscape features. We also gathered information about the invasion process through interviews with rural settlers. The species’ distribution was calculated with the Minimum Convex Polygon method, and a linear invasion rate was calculated. Finally, a map with priority areas for eradication was developed. Armadillos occur in areas with tall and medium-height vegetation and avoid low and floodable terrains. Signs of armadillo presence were more abundant in areas with humic soils but were not associated with any landscape features. The distribution of C. villosus increased by 4735.92 km2 in 12 years with an average linear expansion rate of 10.91 km/year. Humans seem to have facilitated the spread of armadillos towards the south. Implementation of any control measures should be focused on two areas of the island: namely those with high terrains, medium/high vegetation height and humic soils. This invasion represents a socio-ecological problem that needs full and urgent attention while eradication is still feasible.