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

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.