Brill Academic Publishers
We tested two hypotheses proposed to explain why many birds emit distress calls when in the grasp of a predator: the startle-predator and predator-attraction hypotheses. Responses of captive coyotes to a starling distress call were compared between no-call and call trials to determine whether coyotes are startled by the call, and if so, whether they habituated to it. The coyotes were then paired and re-tested to determine whether the call incites a second coyote to approach and interfere with the attack of the initial coyote. Most coyotes exhibited a startle response during their first exposure to the distress call, their total startle response and total attack time significantly increased, and number of tugs on the prey significantly decreased in initial response to the call. However, distress calls may only startle naive or inexperienced predators because the coyotes habituated rapidly to the distress call playback.
Although coyotes were attracted by the starling distress call, this study provided no evidence indicating that the call caused attracted coyotes to disrupt the attack of the first coyote. Furthermore, when an attracted coyote physically interfered, it frequently induced an intensified attack on the prey by the first coyote.
Knowlton, Frederick F.; Conover, Michael R.; and Wise, Kristi K., "Response of coyotes to avian distress calls : testing the startle-predator and predator-attraction hypotheses" (1999). Wildland Resources Faculty Publications. Paper 1580.