White-winged vampire bats (Diaemus youngi) exchange contact calls

Temporally precise vocal exchanges, termed "antiphonal calling", might allow pair or group members to maintain social contact with greater efficiency than when calling independently. The white-winged vampire bat (Diaemus youngi (Jentink, 1893)) is a group-living species that produces social calls in antiphonal exchanges. Because white-winged vampire bats can use social calls to discriminate conspecifics, we suspect that one function of these vocal exchanges is to allow group members to know who is where. Here, we tested the prediction that antiphonal calling by groups of whitewinged vampire bats increases when the spatial positions of conspecifics change. We recorded social calls from groups of four individually caged bats in total darkness, with each bat located in the corner of a 4 m × 4 m room. During test trials, we shifted the spatial positions of caged bats to new positions. During control trials, caged bats were displaced an equal distance but were returned to their original positions. We found that both the number of social calls and the proportion of antiphonal exchanges were greater during test trials than during control trials. These results suggest that white-winged vampire bats use antiphonal exchanges of social calls to monitor the spatial positions of conspecifics.