Eastern gray squirrels (Sciurus carolinensis) and some species of songbirds are both preyed on by red-tailed hawks. A study released September 4 in PLOS ONE suggests that squirrels modify their vigilance behavior based on “bird chatter,” the chirps that birds make while at rest, in addition to bird alarm calls.
A team led by biologist Keith Tarvin at Oberlin College played recordings of hawk calls to 67 gray squirrels found in parks and residential areas in Oberlin, Ohio. They followed the hawk tape with playback of either bird chatter or ambient noise without bird chatter. The squirrels that heard bird sounds after the hawk call showed a faster drop off in vigilance behaviors, such as freezing in place or fleeing, and they also looked upward less, The Guardian reports.
“When squirrels are hearing chatter coming from other birds, that chatter conveys a message or a cue that apparently these birds feel pretty safe,” says Tarvin to NPR. “And the squirrels apparently interpret that to mean that the environment is relatively safe.”
Squirrels have been known to adjust their behavior after hearing bird alarm calls, but the new study is the first to suggest that squirrels also make use of non-alarm-related birdsong. “The study calls attention to how animals can gather information from their environment by using cues that may at first glance seem irrelevant,” Jakob Bro-Jorgensen, an evolutionary ecologist at the University of Liverpool who was not involved in the study, tells The Guardian. “And it makes you wonder how the more and more pervasive impact of human activities on natural soundscapes may compromise survival of wildlife in ways we haven’t thought of.”
Emily Makowski is an intern at The Scientist. Email her at firstname.lastname@example.org.