Lizard calls convey honest information on body size and bite performance: a role in predator deterrence?

Abstract

When encountering predators, prey animals often signal their ability to fight or flee to discourage the predator from an attack or pursuit. A key requirement for evolutionary stability of these predator-deterrent signals is that they convey honest information on the prey’s fighting or fleeing performance. In this study, we investigate the enigmatic ‘distress call’ of the lacertid lizard Psammodromus algirus, and test whether it conveys reliable information on an individual’s body size, and bite and sprint performance. Our acoustic analyses revealed a complex spectral structure in the vocalization of P. algirus, showing a wide frequency bandwidth, multiple harmonics, and a marked frequency modulation. This spectral design may allow such calls to be perceived by multiple potential predators, as it was assessed by a literature search comparing the call frequency range with the hearing ranges of P. algirus’ top predators. In addition, we found considerable inter-individual variation in the call design of lizards (‘call signatures’), which was linked with inter-individual variation in body size and maximum bite force, but not with sprint speed (a proxy of escape performance). As a whole, our study supports the hypothesis that the vocalizations of P. algirus lizards have the potential to serve as honest calls to deter predators. Further research on the behavioural response of predators towards lizard calls is essential in order to unravel the true predator deterrence potential of these calls. When eye-to-eye with a predator, prey animals may signal their ability to fight or flee to convince the predator not to attack or pursue them. Reptiles typically use visual displays to deter predators, but fascinatingly, Psammodromus algirus lizards have been observed to vocalize when encountered by predators. Here, we explored the acoustic properties of these calls and examined whether they convey honest information on a lizard’s fighting and fleeing performance. Our recordings indicate that the acoustic profile of the calls fall within the hearing sensitivity of the lizard’s top predators. Moreover, our experiments show a significant link between the acoustic profile of lizard calls and lizard fighting ability, but not with fleeing ability. Together, our results imply that these lizard calls have predator deterrence potential. Additionally, this study provides the first evidence of honest acoustic signalling of performance in a reptile.