Animal Alarm Calls

Alarm calls are broadly defined as calls occurring in a predator context. Alarm calls have been the subject of intense scrutiny in animal communication research, as they are relevant to core conceptual questions—from the survival value of signaling to the cognitive mechanisms underpinning alarm call production and comprehension. Alarm calls may have several functions, including warning conspecifics, reducing signaler predation risk, mobbing, deterring predators from pursuit, and displaying signaler quality. Some species have evolved different types of alarm calls in response to different types of predators, with more specific calls typically given in response to aerial predators, while calls given in response to terrestrial predators may also occur in aggressive contexts, such as intergroup encounters and during male-male competition and are thus less specific. A key question in the evolution of alarm calls is to what degree kin selection individual selection, and sexual selection shape alarm calling. Alarm calls that elicit escape responses in group members are typically attributed to kin selection, whereas pursuit-deterrent calls likely evolved to manipulate predators and are considered products of individual selection. Mobbing calls manipulate the behavior of both conspecifics and predators. Male alarm calls also function as quality signals and are likely subject to sexual selection. Assessing the putative costs of alarm calling, i.e., the elevated risk of predation, is essential for understanding their evolution. The empirical basis for assessing the risk associated with alarm calling is still scant, however. Because the occurrence of alarm calls can typically be linked to a specific external event—the appearance of a predator—they have played a prominent role in elucidating the cognitive mechanisms underpinning signal production and comprehension. Context-specific alarm calls sparked fundamental questions regarding the concept of meaning and the question of reference in animal communication. The structure of alarm calls is generally viewed as largely innate, while learning plays a major role in the understanding of and responses to alarm calls. There is no evidence that alarm calls are symbolic or conventionalized; thus the similarities between context-specific alarm calls and human speech are limited to the recipients’ attribution of meaning, while the production of alarm calls differs fundamentally from the production of speech. There is ample evidence that alarm calls are valuable sources of information for other prey species as well (“eavesdropping”) and there are several reports regarding functional deception, which may either be selected for or have developed as a result of learning.