The importance of group vocal behaviour in roost finding

Individuals benefit from socially acquired information to avoid predation risks and enhance foraging efficiency. Spix's disc-winged bats, Thyroptera tricolor, form very stable social groups despite their need to find a new roosting site daily. Thyroptera tricolor produce two contact calls: inquiry calls, emitted during flight, and response calls, produced by bats after finding a suitable roost (in a furled leaf). Bats within social groups exhibit consistent individual differences in vocal behaviour and thus, groups are composed by a mix of less vocal and more vocal individuals. To date, it is not known whether consistent individual differences in contact calling behaviour decrease the time required for roost finding and whether vocal behaviour is correlated with an individual's ability to quickly locate roosts, thus constituting a behavioural syndrome. Here, we compared the time spent by social groups in finding roosts when a bat called from inside the roost, either frequently or infrequently. Moreover, we estimated how well calling rates inside a roost predicted a bat's ability to later find a new roost. Results of behavioural experiments and field observations show that social groups enter roosts faster when the bat inside the roost called more. This suggests that more frequent calling decreases search time, which may allow groupmates to save energy and decrease exposure to predators. Moreover, vocal activity also predicted discovery of more roosts (furled leaves) in their natural habitat, which emphasizes the relevance of more vocal individuals for the group. Our work represents a step in understanding the importance of communication and individual vocal behaviour in group formation and stability in gregarious animals.