Shock or jump: deimatic behaviour is repeatable and polymorphic in a yellow-bellied toad

Abstract

Inter-individual variation in antipredatory strategies has long attracted curiosity among scientists. Deimatisms is a complex and time-structured antipredatory strategy consisting in prey suddenly unleashing unexpected defences to frighten predators and stop their attack. Being deimatism traditionally considered as a stereotyped antipredatory response, the inter-individual variation in phenotypic traits related to deimatic displays is almost unexplored. In this study, we employed common garden experiments on 71 yellow-bellied toad Bombina pachypus to investigate the extent and pattern of inter-individual variation in the unken-reflex behaviour, a deimatic display performed by some amphibians. Results show that deimatic displays consistently differ among individuals. Only about half of the individuals reacted to the predation stimuli by exhibiting the display, which varied in responsiveness, duration and intensity. All the investigated descriptors were repeatable (R > 0.50, p < 0.01). Finally, we found significant correlations between the measured parameters, defining two alternative behavioural profiles: individuals quickly doing unken-reflex, with high intensity and long duration of the display, and individuals avoiding unken-reflex but rather escaping. Such dichotomy resembles respectively the proactive and reactive coping styles. Such an unexpected variation in deimatic behaviour raises intriguing questions on the evolutionary processes shaping multiple adaptive responses to predation within populations.