Post-establishment changes in habitat selection by an invasive species: beavers in the Patagonian steppe.
Changes in habitat use over the course of a biological invasion may influence the fraction of the landscape that is ultimately affected by the invader. However, this intermediate stage of invasion has been less studied than the initial or final stages. Here, we investigated the recent invasion by an ecosystem engineer, the American Beaver (Castor canadensis), in an area of the Patagonian steppe. We utilized repeated high resolution satellite images to identify beaver ponds, and used them to study changes in beaver abundance and habitat use over time. The number of beaver ponds increased 85% between 2005 and 2014. During this period, beavers changed their habitat selection pattern, presumably as a response to increased density. Beavers established on small watercourses in canyons first, but as more canyons became occupied over time, beavers moved to less preferred watercourses in plains and U-shaped valleys. Potential new beaver colonies established close to existing beaver ponds, suggesting proximity to a beaver pond is an important determinant of beaver colonization. Identifying habitat preferred by beavers in the steppe, could help to increase early detection of the invader at the invasion front. Our work highlights the importance of the use of high resolution remote sensing technologies to better understand and control biological invasions.