Geographic variation in marmots’ alarm calls causes different responses

Abstract

Geographic variation in acoustic signals has been investigated for five decades to better understand the evolution of communication. When receivers are able to discriminate among signals and to react accordingly, geographic variation can have major impacts on the ability of conspecifics to communicate. Surprisingly, geographic variation in alarm calls and its consequences for the communication process have been so far neglected despite their crucial role on individual survival. Working with four wild populations of Alpine marmots (Marmota marmota), we found differences in the acoustic structure of their alarm calls. These differences cannot be explained by geographic or genetic distances but more likely by other mechanisms including random processes. Moreover, playback experiments provided evidence that receivers discriminate between alarm calls from their own versus other populations, with responses at lower intensity when the alarm calls played back originated from their own population. Research on the mechanistic causes of geographic variation and on the relationship between alarm call variation, familiarity, and intelligibility of signal and behavioral responses is now required to better understand how predation pressure, and more widely natural selection, could drive the evolution of communication. Dialects (i.e., geographic variation) can have major impacts on the ability of conspecifics to communicate. Surprisingly, dialects in alarm calls have been neglected despite their crucial role on survival of individuals. Alpine marmots have dialects in alarm calls and discriminate their own dialects from others, being more frightened by alarm calls from another population than by those from their own. Confronted with an unknown dialect, marmots may adopt a self-preserving strategy and choose to run away before assessing the danger.