Interspecies communication and alarm call eavesdropping on multiple birds by a sympatric mammal

Just as communication within a species can have multiple functions, the same is true for communication between species; interspecies communication is possible, so long as two interacting species use the same general mode of communication, such as auditory, and overlap in the range of signals they can perceive. Functions for such communication includes evading predators, capturing prey, cooperating with or cheating off of competitors, forming partnerships with the enemy of an enemy (cross-trophic alliances), and receiving predator information from members of the same prey guild. Recent research has documented several examples of responses to heterospecific alarm signals in both aquatic and terrestrial realms; of particular interest are cases of alarm communication between very distantly related species, as between birds and mammals. I sought to investigate such bird-mammal communication between the California ground squirrel (Otospermophilus beecheyi) and four sympatric bird species, using field playback of bird calls to wild squirrel colonies. I hypothesized that bird alarm calls, indicating predation threat, would result in increased vigilance, causing both increased escape behavior and greater allocation to vigilance behavior, while bird songs, representing a lack of danger, would have the opposite result. I found that for three of the four sympatric bird species' calls, squirrels increased vigilance in response to alarms but did not change their vigilance in response to songs. This response is the broadest ever demonstrated for bird-mammal alarm communication. A single species of mammal responds to alarm calls from birds representing three different genera and two different biological orders.