Newswise — Grey squirrels eavesdrop on the chatter between nearby songbirds as a sign of safety, according to a paper by Marie Lilly and colleagues at Oberlin College in the United States, publishing September 4, 2019 in the open-access journal PLOS ONE.
Many songbirds produce alarm calls to warn members of their flock about potential danger, such as a nearby bird of prey, but they also call to each other when they feel safe to communicate the absence of danger or share their location. This “chatter” from multiple bird species could therefore be a useful cue to other creatures that there is no imminent threat.
To test this hypothesis, the researchers observed the behavior of 54 wild Eastern gray squirrels (Sciurus carolinensis) in public parks and residential areas in Ohio in response to threat, which they simulated by playing back a recording of the call of a red-tailed hawk (Buteo jamaicensis), a common predator of both squirrels and small birds. They followed the predator’s call with a playback of either multi-species songbird bird chatter or ambient sounds lacking bird calls and monitored the behavior of each squirrel for 3 minutes.
The researchers found that all squirrels showed an increase in predator vigilance behaviors, such as freezing, looking up, or fleeing, after they heard the hawk’s call. However, squirrels that were played bird chatter afterwards performed fewer vigilance behaviors and returned to normal levels of watchfulness more quickly than squirrels that did not hear bird calls after the hawk’s call. This suggests that the squirrels are able to tap into the casual chatter of many bird species as an indicator of safety, allowing them to quickly return to getting on with normal behaviors like foraging rather than remaining on high alert after a threat has passed.
The authors add: “We knew that squirrels eavesdropped on the alarm calls of some bird species, but we were excited to find that they also eavesdrop on non-alarm sounds that indicate the birds feel relatively safe. Perhaps in some circumstances, cues of safety could be as important as cues of danger.”
Press-only preview: https://plos.io/3494R8c
Image Caption: Listening grey squirrel
Image Credit: Illustration based on the photograph (Emma C. Lucore ) by Marie V. Lilly (2019)
Funding: This study was funded by a Grant-in-aid from Oberlin College and the Oberlin College Lee Drickamer '67 Research Support Fund. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.