Individual, age and sex-specific information is contained in yellow-bellied marmot alarm calls

Individuals produce distinctive vocalizations that may contain considerable potential information about a signaller. Simply finding significant covariation between call structure and some individual attribute does not itself mean that there has been selection on callers to produce individually distinctive calls, nor on receivers to discriminate between them. Moreover, acoustic variation may degrade while being transmitted through the environment, making it potentially difficult for receivers to extract potential information. We focused on the individually distinctive calls of yellow-bellied marmots, Marmota flaviventris, to describe attributes of individuals encoded in calls. Using discriminant function analysis, we found significant potential information about identity, age and sex encoded in calls. When calls were broadcast and re-recorded over 10 m and 40 m, identity, age and sex remained statistically discriminatable. Key variables that enabled discrimination were repeatable (they had high intraclass correlation coefficients), whereas those that did not enable discrimination were less repeatable. Finally, statistics developed to describe, in a standardized and comparative way, the information about individual signallers contained in vocalizations, revealed that marmot alarm calls contained at least 3.37 bits of information about identity. When compared to other species for which the information content of signals has been calculated, marmots may have not undergone strong selection for individually distinctive vocalizations. The fact that receivers discriminate between individuals suggests that receivers benefit by doing so.