Animals foraging in the dark are simultaneously engaged in prey pursuit, collision avoidance and interactions with conspecifics, making efficient, non-visual communication essential. A variety of birds and mammals emit food-associated calls that inform, attract, or repel conspecifics [e.g., 1]. Big brown bats (Eptesicus fuscus) are insectivorous aerial hawkers that may forage near conspecifics and are known to emit social calls [e.g., 2, 3, 4, 5]. Calls recorded in a foraging setting might attract [e.g., 6] or repel conspecifics [7] and could denote territoriality or food-claiming. Here, we provide evidence that a social call emitted only by male bats, exclusively in a foraging context [5], the “frequency-modulated bout” (FMB), is used to claim food and is individually distinct. Bats were studied individually and in pairs in a flight room equipped with synchronized high-speed stereo video and audio recording equipment, while sex and experience with a foraging task were experimentally manipulated. Male bats emitting the FMB showed greater success in capturing prey. Following FMB emission, inter-bat distance, diverging flight, and the other bat’s distance to the prey each increased. These findings highlight the importance and utility of vocal communication for a nocturnal animal mediating interactions with conspecifics in a fast-paced foraging setting.

Vocalizations serving a variety of social functions have been reported in many bat species (Order Chiroptera). While echolocation by big brown bats (Eptesicus fuscus) has been the subject of extensive study, calls used by this species for communication have received comparatively little research attention. Here, we report on a rich repertoire of vocalizations produced by big brown bats in a large flight room equipped with synchronized high speed stereo video and audio recording equipment. Bats were studied individually and in pairs, while sex, age, and experience with a novel foraging task were varied. We used discriminant function analysis (DFA) to classify six different vocalizations that were recorded when two bats were present. Contingency table analyses revealed a higher prevalence of social calls when males were present, and some call types varied in frequency of emission based on trial type or bat age. Bats flew closer together around the time some social calls were emitted, indicating that communicative calls may be selectively produced when conspecifics fly near one another. These findings are the first reports of social calls from flying big brown bats and provide insight into the function of communicative vocalizations emitted by this species.

Acquiring information via observation of others can be an efficient way to respond to changing situations or learn skills, particularly for inexperienced individuals. Many bat species are gregarious, yet few studies have investigated their capacity for learning from conspecifics. We tested whether big brown bats (Eptesicus fuscus) can learn a novel foraging task by interacting with knowledgeable conspecifics. In experimental trials 11 naïve bats (7 juveniles, 4 adults) interacted freely with trained bats that were capturing tethered mealworms, while in control trials 11 naïve bats (7 juveniles, 4 adults) flew with untrained bats. Naïve bats were then assessed for their ability to capture tethered mealworms. While no bat in the control group learned the task, a significant number of experimental bats, including juveniles with little or no experience foraging, showed evidence of learning. Eighty-two per cent of experimental bats and 27% of control bats directed feeding buzzes (echolocation calls associated with prey capture) at the mealworm. Furthermore, seven experimental bats (64%) showed evidence of learning by attacking and/or capturing the mealworm, while no bat in the control group attacked or captured the prey. Analyses of high-speed stereo video recordings revealed increased interaction with demonstrators among bats attacking or capturing the mealworm. At the time they displayed evidence of learning, bats flew closer together during feeding buzzes than during other portions of trials. Our results demonstrate that social interaction with experienced bats, and listening to feeding buzzes in particular, may play an integral role in development of foraging skills in bats.

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Group-living animals can potentially enhance their foraging performance and efficiency by obtaining information from others. Using PIT-tag data to study foraging behaviour in individual bats, we tested short-tailed fruit bats, Carollia perspicillata (Linnaeus), for evidence of local enhancement or social facilitation. To discriminate between these phenomena, we manipulated the presence of conspecifics while individuals searched for food. We quantified the time to find food and the order and sex of bats accessing the food, and any consistent associations between bats. Presence of conspecifics decreased the time needed to find food. We found no evidence that pairs of individuals consistently fed together; however, bats of the same sex tended to feed closer in time with one another. The same individuals consistently accessed the food first, and males found food more quickly than females. Our results provide evidence of social facilitation, with bats finding food more quickly in a group than alone.

Animals foraging in the dark must simultaneously pursue prey, avoid collisions, and interact with conspecifics, making efficient non-visual communication essential. A variety of birds and mammals emit food-associated calls that inform, attract, or repel conspecifics. While echolocation by the insectivorous, aerial-hawking big brown bat (Eptesicus fuscus) has been studied extensively, communicative calls used by this species have received comparatively little research attention. We report on a rich repertoire of vocalizations produced by big brown bats in a large flight room equipped with synchronized high-speed stereo video and audio recording equipment. We also provide evidence that a specific social call, the “frequency-modulated bout” (FMB), which is emitted only by males, exclusively in a foraging context, and only when conspecifics are present, predicts the caller’s foraging success and is individually distinct. Bats were studied individually and in pairs, while sex and experience with a foraging task were experimentally manipulated. Individuals emitting a higher number of FMBs showed greater prey capture success. Following FMB emission, inter-bat distance, diverging flight, and the other bat’s distance to the prey increased. These findings highlight the importance of vocal communication for nocturnal animals mediating interactions in a fast-paced foraging setting.

While the echolocation calls of big brown bats (Eptesicus fuscus) have been studied extensively, this species’ communicative vocalizations have received little attention. Calls were recorded from pairs of bats flying in a laboratory flight room in a foraging context. Pairs consisted of naive bats flown with individuals that were either experienced about how to take a tethered insect or naive or of two experienced bats flying together. This situation elicited a variety of vocalizations with properties different from typical E. fuscus echolocation calls. Seven different call shapes that occurred only when two bats were present were identified and categorized. These included chirp-like calls, rising frequency calls, calls that were longer than 20 ms in duration, and series of ultrasonic, chirp-like calls (or “songs”) produced only by male bats and displaying individual variation. Some call types were only recorded when a juvenile was present or very rarely in adult-only pairs. Using high-speed video data collected in synchrony with the audio recordings, the contexts and possible functions of various calls are evaluated. The rate at which different call types were recorded with regard to bats’ knowledge of the foraging task and the age and sex of bats flown together is also considered.