Eavesdropping grey squirrels infer safety from bird chatter

Area of Science:

• Behavioral Ecology
• Interspecies Communication
• Animal Behavior

Background:

• Species vulnerable to common predators benefit from environmental information shared by other species.
• Eastern gray squirrels (Sciurus carolinensis) exploit heterospecific alarm calls, but less is known about their response to non-alarm cues.

Purpose of the Study:

• To test if gray squirrels interpret "bird chatter" (non-alarm bird contact calls) as a cue of safety.
• To investigate if squirrels adjust vigilance behavior based on auditory cues from other species indicating low predation risk.

Main Methods:

• Playback experiments with free-ranging eastern gray squirrels.
• Priming squirrels with a predator cue (red-tailed hawk call) followed by "bird chatter" or ambient noise.
• Comparing vigilance behaviors (e.g., looking up, freezing, fleeing) between the two playback conditions.

Main Results:

• Squirrels significantly increased vigilance after hearing a hawk call, confirming perceived threat.
• Following the threat cue, squirrels exposed to "bird chatter" exhibited significantly lower vigilance levels compared to those exposed to ambient noise.
• The decay in vigilance behavior was more rapid in the "bird chatter" group, suggesting a quicker return to non-vigilant states.

Conclusions:

• Eastern gray squirrels eavesdrop on non-alarm auditory cues from other species.
• Squirrels use "bird chatter" as an indicator of safety, modulating their vigilance behavior accordingly.
• This demonstrates interspecific eavesdropping on safety signals, influencing predator-prey dynamics.