Introduced Muskrats (Ondatra zibethicus) on Navarino Island, Cape Horn, Chile: Physical Signs, Habitat Associations, and Interactions with Introduced Beaver (Castor canadensis)

Research on non-native species in the Cape Horn region of southern Chile has focused on the American mink and The American beaver, but ignored the muskrat. We surveyed freshwater habitats on Navarino Island, Cape Horn to identify physical signs of muskrat presence and to document muskrat habitat use. Muskrat presence/absence was compared with beaver altered habitat to determine if the ecosystem changes produced by beaver benefit muskrat. Latrines, tracks, and houses were the most common indicators of muskrat presence. Muskrat presence was associated with an increased abundance of aquatic vegetation, slow water velocity, and increased bank vegetation cover. Habitat conditions favored by muskrat tended to co-occur with habitat impacted by beaver and muskrat presence was strongly associated with beaver altered habitat. These results suggest a commensal relationship where the ecosystem engineering activity of the introduced American beaver creates habitat more favorable to introduced muskrat in the Cape Horn region.