Eavesdropping of woodchucks (Marmota monax) and eastern chipmunks (Tamias striatus) on heterospecific alarm calls

Individuals of 1 species might obtain information by eavesdropping on calls produced by a syntopic species. Intercepting alarm calls allows the eavesdropper to respond with antipredator behavior without the need to produce its own call, which might attract the attention of a predator. We examined eavesdropping on heterospecific alarm calls by nonsocial eastern chipmunks (Tamias striatus) and woodchucks (Marmota monax), which live in the same community, share some predators, are solitary, and produce distinct alarm calls. If these 2 species recognize heterospecific alarm calls, we should see antipredator behaviors similar to those displayed upon hearing a conspecific's alarm call. We broadcast single alarm calls of woodchucks, eastern chipmunks, and American crows (Corvus brachyrhynchos) to individuals of the first 2 species, using the territorial song of the syntopic male black-capped chickadee (Poecile atricapillus) as a control. Woodchucks became more vigilant after hearing both conspecific and heterospecific alarm calls compared with controls; however, they spent more time vigilant in response to conspecific alarm calls compared to heterospecific alarm calls. Thus, woodchucks apparently can recognize heterospecific alarm calls, but they appear to process conspecific and heterospecific calls differently. Eastern chipmunks responded to heterospecific alarm calls, but sample sizes were small and the results not definitive. Our results suggest that nonsocial mammals might benefit from eavesdropping on heterospecifics.