![]() Importantly, valuable public information may stem from heterospecific sources. Eavesdropping on each of these types of public information allows individuals to reduce their own costs of vigilance and in some cases they may rely on these environmental cues of predation risk. Indeed, even the abrupt cessation of non-alarm vocalizations, as sometimes occurs in response to the sudden appearance of a predator, can elicit antipredator behaviors in eavesdroppers (e.g., ). Like alarm calls, sentinel communications prompt adaptive changes in vigilance behavior from listeners. For example, individuals of some group-living species act as lookouts and provide both alarm calls in the presence of danger and “sentinel” or “all-clear” calls in the absence of danger, such as when a predator leaves an area or following false alarms. Public information about predation risk frequently takes the form of alarm signals, but non-alarm signals of safety also can be informative. This in turn allows individuals to allocate more time and energy toward foraging and other tasks. Exploitation of information about predator threat generated by other animals can benefit individuals by reducing the amount of time and energy they must allocate toward vigilance, while increasing the likelihood of avoiding predation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist.Įavesdropping on public information to assess predation risk is common across a wide array of vertebrate taxa. ![]() This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.ĭata Availability: All data are within the manuscript and its Supporting Information file.įunding: This study was funded by a Grant-in-aid from Oberlin College and the Oberlin College Lee Drickamer '67 Research Support Fund. Received: FebruAccepted: AugPublished: September 4, 2019Ĭopyright: © 2019 Lilly et al. PLoS ONE 14(9):Įditor: Vivek Nityananda, Newcastle University, UNITED KINGDOM These findings suggest that eastern gray squirrels eavesdrop on non-alarm auditory cues as indicators of safety and adjust their vigilance level in accordance with the vigilance level of other species that share the same predators.Ĭitation: Lilly MV, Lucore EC, Tarvin KA (2019) Eavesdropping grey squirrels infer safety from bird chatter. Following the hawk playback, squirrels exposed to the chatter treatment engaged in significantly lower levels of vigilance behavior (i.e., standing, freezing, fleeing, looking up) and the decay in vigilance behaviors was more rapid than in squirrels exposed to the ambient noise treatment, suggesting squirrels use information contained in bird chatter as a cue of safety. ![]() Squirrels responded to the hawk call playbacks by significantly increasing the proportion of time they spent engaged in vigilance behaviors and the number of times they looked up during otherwise non-vigilance behaviors, indicating that they perceived elevated predation threat prior to the playbacks of chatter or ambient noise. We compared vigilance behavior of free-ranging squirrels in the presence of playbacks of bird chatter vs non-masking ambient background noise lacking chatter after priming them with a playback recording of a red-tailed hawk ( Buteo jamaicensis) call. We tested the hypothesis that eavesdropping gray squirrels respond to “bird chatter” (contact calls emitted by multiple individuals when not under threat of predation) as a measure of safety. However, many species–especially birds-emit non-alarm auditory cues such as contact calls when perceived predator threat is low, and such public information may serve as cues of safety to eavesdroppers. ![]() Eastern gray squirrels ( Sciurus carolinensis) and other small mammals have been shown to exploit heterospecific alarm calls as indicators of danger. ![]() When multiple species are vulnerable to a common set of predators, it is advantageous for individuals to recognize information about the environment provided by other species. ![]()
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