Conspecifics influence call design in the Brazilian free-tailed bat, Tadarida brasiliensis

SUMMARYNaïve red (Lasiurus borealis Müller) and big brown (Eptesicus fuscus Beauvois) bats quickly learn to avoid noxious soundproducing tiger moths. After this experience with a model tiger moth, bats generalize the meaning of these prey-generated sounds to a second tiger moth species producing a different call. Here we describe the three-dimensional kinematic and bioacoustic details of this behaviour, first, as naïve bats learn to deal with an unpalatable model tiger moth and subsequently, as they avoid acoustic mimics. The tiger moths' first clicks influenced the bats' echolocation behaviour and the percentage of interactions that included terminal buzzes was associated with capture and investigatory behaviour. When the mimic was introduced, the bats decreased both their minimum distance to the tiger moth and the time at which they broke off their attack compared with their exposure to the model on the night before. These kinematic signatures closely match the bats' behaviour on their first night of experience with the model. Minimum distances and time of pursuit cessation increased again by the last night of the mimic's presentation. These kinematic and bioacoustic results show that although naïve bats generalize the meaning of aposematic tiger moth calls, they discriminate the prey-generated signals as different and investigate. Extrapolating to experienced bats, these results suggest that acoustic predators probably exert potent and fine-scaled selective forces on acoustic mimicry complexes. Supplementary material available online at

Section: Bioacousticssupporting

confidence: 72%

Naïve bats discriminate arctiid moth warning sounds but generalize their aposematic meaning

Barber

Chadwell

Garrett

et al. 2009

“…The lengthening of call durations that we observed may be an attempt to do the same. Bats also shift call frequency in order to avoid jamming by conspecifics Ratcliffe et al, 2004;Ulanovsky et al, 2004), chorusing insects and synthetic narrowband noise (Bates et al, 2008;Tressler and Smotherman, 2009), but not broadband noise (Bates et al, 2008;Tressler and Smotherman, 2009). We did not observe bats changing the frequency of their emissions in response to moth clicks, only the durations and pulse intervals.…”

Section: Bat Echolocation and Flight Responses To Moth Clicks Supportmentioning

confidence: 99%

How do tiger moths jam bat sonar?

Corcoran

Barber

Hristov

et al. 2011

SUMMARYThe tiger moth Bertholdia trigona is the only animal in nature known to defend itself by jamming the sonar of its predators -bats. In this study we analyzed the three-dimensional flight paths and echolocation behavior of big brown bats (Eptesicus fuscus) attacking B. trigona in a flight room over seven consecutive nights to determine the acoustic mechanism of the sonar-jamming defense. Three mechanisms have been proposed: (1) the phantom echo hypothesis, which states that bats misinterpret moth clicks as echoes; (2) the ranging interference hypothesis, which states that moth clicks degrade the bats' precision in determining target distance; and (3) the masking hypothesis, which states that moth clicks mask the moth echoes entirely, making the moth temporarily invisible. On nights one and two of the experiment, the bats appeared startled by the clicks; however, on nights three through seven, the bats frequently missed their prey by a distance predicted by the ranging interference hypothesis (~15-20cm). Three-dimensional simulations show that bats did not avoid phantom targets, and the bats' ability to track clicking prey contradicts the predictions of the masking hypothesis. The moth clicks also forced the bats to reverse their stereotyped pattern of echolocation emissions during attack, even while bats continued pursuit of the moths. This likely further hinders the bats' ability to track prey. These results have implications for the evolution of sonar jamming in tiger moths, and we suggest evolutionary pathways by which sonar jamming may have evolved from other tiger moth defense mechanisms. Supplementary material available online at

“…Call design separation was affected by the spatial distance between paired bats and baseline similarity in call design, which further suggests that the bat actively adjusts its call design to avoid signal interference from conspecifics. Several bat species, including R. hardwickei, Balantiopteryx plicata, T. brasiliensis and Tadarida teniotis, have been reported to adjust their call frequencies when flying in groups (Bartonicka et al, 2007;Habersetzer, 1981;Ibánez et al, 2004;Ratcliffe et al, 2004;Ulanovsky et al, 2004). Some bat species modified temporal features rather than spectral features of their vocalizations to avoid call interference from conspecifics (Obrist, 1995).…”

Section: Global Signal Adjustments In the Presence Of Conspecificsmentioning

confidence: 99%

Adaptive echolocation behavior in bats for the analysis of auditory scenes

Chiu

Xian

Moss

2009

SUMMARYEcholocating bats emit sonar pulses and listen to returning echoes to probe their surroundings. Bats adapt their echolocation call design to cope with dynamic changes in the acoustic environment, including habitat change or the presence of nearby conspecifics/heterospecifics. Seven pairs of big brown bats, Eptesicus fuscus, were tested in this study to examine how they adjusted their echolocation calls when flying and competing with a conspecific for food. Results showed that differences in five call parameters, start/end frequencies, duration, bandwidth and sweep rate, significantly increased in the two-bat condition compared with the baseline data. In addition, the magnitude of spectral separation of calls was negatively correlated with the baseline call design differences in individual bats. Bats with small baseline call frequency differences showed larger increases in call frequency separation when paired than those with large baseline call frequency differences, suggesting that bats actively change their sonar call structure if pre-existing differences in call design are small. Call design adjustments were also influenced by physical spacing between two bats. Calls of paired bats exhibited the largest design separations when inter-bat distance was shorter than 0.5 m, and the separation decreased as the spacing increased. All individuals modified at least one baseline call parameter in response to the presence of another conspecific. We propose that dissimilarity between the time-frequency features of sonar calls produced by different bats aids each individual in segregating echoes of its own sonar vocalizations from the acoustic signals of neighboring bats.