Experimental evidence for group hunting via eavesdropping in echolocating bats

Abstract

Group foraging has been suggested as an important factor for the evolution of sociality. However, visual cues are predominantly used to gain information about group members' foraging success in diurnally foraging animals such as birds, where group foraging has been studied most intensively. By contrast, nocturnal animals, such as bats, would have to rely on other cues or signals to coordinate foraging. We investigated the role of echolocation calls as inadvertently produced cues for social foraging in the insectivorous bat Noctilio albiventris. Females of this species live in small groups, forage over water bodies for swarming insects and have an extremely short daily activity period. We predicted and confirmed that (i) free-ranging bats are attracted by playbacks of echolocation calls produced during prey capture, and that (ii) bats of the same social unit forage together to benefit from passive information transfer via the change in group members' echolocation calls upon finding prey. Network analysis of high-resolution automated radio telemetry confirmed that group members flew within the predicted maximum hearing distance 94G6 per cent of the time. Thus, echolocation calls also serve as intraspecific communication cues. Sociality appears to allow for more effective group foraging strategies via eavesdropping on acoustical cues of group members in nocturnal mammals.

Social Information Links Individual Behavior to Population and Community Dynamics

“…shared resources or enemies [19]. For instance, echolocation-based foraging in bats produces an easily detectable cue that attracts conspecifics [54] and heterospecifics [55] to resource-rich areas ( Figure 1A). Similarly, chemical and auditory signals drive heterospecific attraction in bees [56] and in ant-following birds [57], respectively, and visual cues drive heterospecific attraction in scavenger birds [58] (Box 1).…”

Low metabolism in a tropical bat from lowland Panama measured using heart rate telemetry: an unexpected life in the slow lane

“…At least some species increase foraging efficiency for this resource by group hunting, indirectly searching a larger area for insect swarms by flying within earshot of roost members and eavesdropping on their echolocation calls (Dechmann et al, 2009;Dechmann et al, 2010). Because of the temporally limited availability of insect prey, some of these species also have short daily activity periods of 1 h or less (Dechmann et al, 2009;Dechmann et al, 2010). They cope with up to 23 h of fasting a day by fuelling flight immediately with lipids from ingested insects (Voigt et al, 2010).…”

Bat echolocation calls facilitate social communication

“…Echolocation signals are not directed at an external receiver per se; nevertheless, they can be used as an information source by eavesdroppers [10 -12]. Echolocation calls indicate both the presence and the feeding activity of bats; therefore, they can inform other bats in hearing distance about good hunting grounds [13,14], new foraging tasks [15] or roost sites [16]. A growing body of evidence indicates that social information about the calling bat can be encoded in echolocation calls as well (reviewed in [11,17]).…”