Common vampire bat contact calls attract past food-sharing partners

Animals living with kin and nonkin should make social decisions based on the consequences for both direct and indirect fitness. Common vampire bats, Desmodus rotundus, invest in stable cooperative relationships that benefit both components of inclusive fitness. To disentangle these two factors, we conducted two types of playback trials using a captive group of familiar common vampire bats with mixed kinship and varying rates of dyadic food sharing. We presented each subject with two speakers, playing contact calls from two different familiar conspecifics. In 'past donor trials', 15 vampire bats chose between calls recorded from either a frequent or rare food donor, but both callers were related to a similar degree with the subject. In 'kinship trials', 31 vampire bats chose between calls recorded from either a close or distant relative, but both callers were matched for food-sharing history with the subject. We found that vampire bats were attracted to contact calls of frequent food donors when controlling for kinship, but not to calls of kin when controlling for food-sharing history. Responses and acoustic analyses suggested that bats recognized individuals from vocalizations. These results corroborate past findings that prior food sharing can overshadow relatedness in determining the social decisions of vampire bats. Common vampire bat contact calls allow food-sharing partners to recognize and find each other at a distance, which likely enables them to switch roosts together in the wild.