HABITAT USE BY INVASIVE NORTH AMERICAN BEAVER DURING INTERMEDIATE AND LONG-TERM COLONIZATION PERIODS IN SOUTHERN PATAGONIA.

Since their introduction to southern Patagonia in 1946, North American beavers (Castor canadensis) have become a major impact to streams and forests. Scientists and managers now call for their eradication, requiring research to orient actions. John et al. (2010) showed that predicting beaver presence, which is crucial to plan eradication efforts, varies throughout colonization time (initial = unpredictable occupation of random sites; intermediate = predictable occupation of optimal sites; long-term = unpredictable occupation of sub-optimal locations). Beaver presence/absence and habitat variables (geomorphology, soil, and vegetation) were measured in the field and from satellite images in sites colonized at intermediate (Brunswick Peninsula ~1994) and long-term (Navarino Island ~1960) periods to predict this species' habitat use. Habitat suitability models were constructed using generalized linear models with those variables significantly different between sites with and without beaver. As hypothesized, a significant explanatory habitat model could not be developed for long-term occupation sites. However, beaver presence was predictable at intermediate colonization sites, and the best significant model included only river sinuosity and explained 74% of data variability. The model suggested that beavers used areas with greater river sinuosity, which could be measured from satellite images. Since remotely-sensed information requires less field effort, this approach could be useful in southern Patagonia's remote areas, where access is difficult. Additionally, these findings highlight the overall difficulty of planning a large-scale beaver eradication program and predicting beaver habitat use across a gradient of habitat types and colonization stages. [ABSTRACT FROM AUTHOR]