The In-Flight Social Calls of Insectivorous Bats: Species Specific Behaviors and Contexts of Social Call Production

Abstract

Bats could be a useful study system for studying the evolution of social communication, as they exhibit a high diversity of social group size and complexity. However, the study of bat social calls has been limited, as they are nocturnal, volant animals that produce predominately ultrasonic vocalizations. Passive acoustic monitoring studies occasionally capture bat in-flight social calls. The information from surrounding echolocation calls can provide information on species identity, abundance, and foraging activity. I used passive acoustic monitoring in Greensboro, North Carolina, to identify seven types of in-flight social calls from Eptesicus fuscus, Lasiurus borealis, Lasiurus cinereus, Nycticeius humeralis, Perimyotis subflavus, and Tadarida brasiliensis. Eptesicus fuscus, N. humeralis, and T. brasiliensis differed in total social call production, and the proportional use of call types. Shared called types exhibited species-specific signatures. The presence of species-specific signatures indicates bats could potentially discern signaler identity. Social call production was highest early in the night and positively correlated with bat activity. Eptesicus fuscus and T. brasiliensis most commonly produced complex calls, which appear to mediate social interactions between conspecifics while foraging. Nycticeius humeralis most commonly produced downsweeps, which appear to be broad-functioning contact calls. Upsweeps exhibited a similar context to downsweeps, and were commonly produced by E. fuscus and N. humeralis. My results indicate bats use dedicated social calls to mediate different types of social interactions while in flight.