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Selection of habitat is a key determinant of reproductive success, and the process of finding and choosing these sites is often influenced by the presence of conspecifics. Many bats frequently switch roosts, and some bats repeatedly find new roosts. To find roosts with conspecifics or group members, bats can use social cues. However, most research on how bats use social cues for roost-finding has focused on acoustic cues. Here, we review and discuss the evidence for bat roost selection using scent cues from guano and urine stains, which are present at most bat roosts. We outline reasons why bats might, or might not, use scent in roost detection and selection, and we review evidence on the possible use of guano and urine in roost-finding from eight studies with 12 bat species (across four families). Overall, the sparse evidence that exists indicates that scent cues from guano and urine are not a strong and consistent lure in the species and situations that were tested. Most studies had unclear results or found no effect. Two of the eight studies found weak experimental evidence for bats using guano or urine to select a roosting site. Even if guano and urine can indicate the presence of bats at a roost, it is possible that the resulting olfactory cues do not contain sufficient social information to be used in roost selection, in contrast to olfactory cues from scent marking. Studies of how bats use sensory cues beyond sound could contribute to a better understanding of bat social behavior and roosting ecology. 

Spatial assortment can be both a cause and a consequence of cooperation. Proximity promotes cooperation when individuals preferentially help nearby partners, and conversely, cooperation drives proximity when individuals move towards more cooperative partners. However, these two causal directions are difficult to distinguish with observational data. Here, we experimentally test if forcing randomly selected pairs of equally familiar female common vampire bats ( Desmodus rotundus ) into close spatial proximity promotes the formation of enduring cooperative relationships. Over 114 days, we sampled 682 h of interactions among 21 females captured from three distant sites to track daily allogrooming rates over time. We compared these rates before, during and after a one-week period, during which we caged random triads of previously unfamiliar and unrelated vampire bats in proximity. After the week of proximity when all bats could again freely associate, the allogrooming rates of pairs forced into proximity increased more than those of the 126 control pairs. This work is the first to experimentally demonstrate the causal effect of repeated interactions on cooperative investments in vampire bats. Future work should determine the relative importance of mere association versus interactions (e.g. reciprocal allogrooming) in shaping social preferences. 

Individual animals across many different species occasionally ‘adopt’ unrelated, orphaned offspring. Although adoption may be best explained as a by-product of adaptive traits that enhance parental care or promote the development of parental skills, one factor that is possibly important for the likelihood of adoption is the history of cooperative interactions between the mother, adopted offspring and adopter. Using 652 h of behavioural samples collected over four months, we describe patterns of allogrooming and food sharing before and after an instance of non-kin adoption between two adult female common vampire bats ( Desmodus rotundus ) that were captured from distant sites (340 km apart) and introduced to one another in captivity. The first female died from an illness 19 days after giving birth. The second female groomed and regurgitated food to the mother more often than any other group member, then groomed, nursed and regurgitated food to the orphaned, female pup. The substantial increase in alloparental care by this female after the mother's death was not observed among the 20 other adult females that were present in the colony. Our findings corroborate previous reports of non-kin adoption in common vampire bats and are consistent with the hypothesis that non-kin adoption can be motivated, in part, by a history of cooperative interactions.