Do Eastern Gray Squirrels Pay Attention to Squirrel Relevant Information Encoded in Black-Capped Chickadee Alarm Calls?

Science Center, Bent Corridor

Many animals eavesdrop on avian alarm calls in order to obtain low-cost information about potential predation risk. Previous research shows that Eastern Gray Squirrels (Sciurus carolinensis) eavesdrop on various bird species, including American Robins (Turdus migratorius) and Black Capped Chickadees (Poecile atricapillus). Our project seeks to investigate whether squirrels respond to information encoded in alarm calls that is explicitly useful to them. Chickadee alarm calls are referential, with calls having a longer series of d-notes indicating a smaller predator, which is a greater threat to the caller (Templeton et. al. 2005). We presented squirrels with audio playbacks of chickadee alarm calls made in response to a mounted Red-Tailed Hawk, a common predator of squirrels, and Saw Whet Owl, not a predator of squirrels, observing changes in squirrel vigilance before and after the playback. We manipulated the number of d-notes in each playback to test whether squirrels respond to variation in the number of d-notes, while controlling for the source of the original alarm recording. We predicted that squirrels would respond more to the calls with fewer d-notes, indicating a larger predator, regardless of the predator used to elicit the original alarm recording. Our results suggest that squirrels do not respond differently to chickadee calls based on the number of d-notes in their call. Instead, squirrels respond with a higher frequency to calls made in response to predators that are relevant to them, which provides compelling evidence that there is another component of the calls that encodes information about predator type.