Abstract
Echolocation and audiovocal communication have been studied extensively in bats. The manner in which these abilities are incorporated within escape behaviors during life-threatening distress is largely unknown. Here we tested the hypothesis that behavioral response profiles expressed during distress are relatively stereotypic given their evolutionary adaptations to avoid predators. We subjected juvenile and adult big-footed myotis (Myotis macrodactylus) to a sequence of three types of life threatening distress: 1) trapping them in a mist-net (environmental threat), 2) approaching them when trapped (predator threat), and 3) partially restraining their freedom to move (arrest), and recorded their escape behavior in each of the three conditions. Response profiles differed across individuals and with the context in which they were expressed. During environmental and predator threat, bats displayed significantly more biting and wing-flapping behaviors and emitted more echolocation pulses than during arrest. Response profiles also varied with age. During arrest, juveniles were more likely than adults to emit distress calls and vice-versa for biting and wing flapping during environmental and predator threat. Overall, individualized response profiles were classified into ten clusters that were aligned along two divergent response trajectories when viewed within two-dimensional, multifactorial decision space. Juvenile behaviors tended to follow a predominantly “social-dependence” trajectory, whereas adult behaviors were mostly aligned along a “self-reliance” trajectory. We conclude that bats modify their vocal behavior and make age-appropriate and contextually adaptive decisions when distressed. This decision-making ability is consistent with observations in other social species, including humans.
Highlights
Given its significance within evolutionary, ecological and neuroethological contexts, bats’ predatory behavior [1,2,3,4] and related neural adaptations for echolocation [5,6,7,8,9] are well studied
Bats may voluntarily adjust certain routine behaviors, such as the choice of day roosts [14] and the timing of departure from a roost [15]. This type of decision making to avoid distress is facilitated by auditory [16], visual [17], and chemical cues [18]
The syllables present within distress calls, were significantly different from echolocation pulses along several other acoustic parameters (Fig 2), so that distinguishing between the two was not a problem
Summary
Given its significance within evolutionary, ecological and neuroethological contexts, bats’ predatory behavior [1,2,3,4] and related neural adaptations for echolocation [5,6,7,8,9] are well studied. Studies of bats’ own escape behavior and how they employ their echolocation and audiovocal communication abilities under life threatening situations, are rare [12,13]. Bats may voluntarily adjust certain routine behaviors, such as the choice of day roosts [14] and the timing of departure from a roost [15]. This type of decision making to avoid distress is facilitated by auditory [16], visual [17], and chemical cues [18]. It is possible that such decision-making in bats is purely reflexive, given their flight and foraging adaptations that naturally insulate them from their predators
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