ABS 2022
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Squirrels eavesdrop on titmouse alarm calls, but do not discriminate squirrel-relevant information
Keith A. Tarvin. Oberlin College, Oberlin, OH, United States

Tufted titmouse (Baeolophus bicolor) alarm calls vary with threat level of avian predators: more urgent calls are given in response to small agile predators, and less urgent calls are given in response to larger, slower predators. Therefore, titmouse alarm calls may vary in their relevance to eavesdropping species as a function of the vulnerability of those eavesdroppers to the predators indicated by the alarm call variants. We tested whether eastern gray squirrel (Sciurus carolinensis) responses to playbacks of titmouse alarms elicited by a stuffed eastern screech owl (Megascops asio) – a minor threat to squirrels – differed from responses to calls elicited by a stuffed red-tailed hawk (Buteo jamaicensis), a dangerous threat to squirrels. Squirrels significantly increased vigilance in response to both types of alarm call. Although squirrel responses to alarms elicited by red-tailed hawks tended to be stronger, they were not significantly different from responses to calls elicited by screech-owls. These results suggest that learning to differentiate titmouse alarm variants is too costly, too risky, or cognitively difficult for squirrels.