Dwarf mongooses use sex and identity cues in isolation calls to discriminate between callers

The information transmitted by acoustic signals has attracted much scientific interest in recent years. However, isolation calls, which are long-distance vocalizations used by lost group members to reunite with their social group, have been surprisingly neglected. These calls assist in maintaining group cohesion and are thus particularly important in species that depend on the group for survival or reproduction such as cooperative breeders. Our study therefore examined the information transmitted by the isolation vocalization in a wild cooperatively breeding carnivore: the dwarf mongoose, Helogale parvula. We ran an acoustic analysis for informative cues within isolation calls, and conducted a series of playback experiments to identify whether mongooses could discriminate between callers based on these cues. The acoustic structure of dwarf mongoose isolation vocalizations contained information concerning the caller's identity, sex and potentially also group membership. Target mongooses discriminated between callers of their own and other groups and biased their response based on the sex of the caller. They responded more quickly and for longer, and approached more closely, for calls of foreign females than calls of female group mates. This is the first time that sex specificity has been demonstrated in the vocalization of an herpestid, and we suggest that dwarf mongooses eavesdrop on the calls of isolated foreigners and may use isolation calls to attract and identify potential mates.