You startle me, you don’t: Antipredatory behaviour differs within populations in an aposematic toad species

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Giuseppe Martino, Roberta Bisconti, Andrea Chiocchio, Claudio Carere and Daniele Canestrelli, Department of Ecological and Biological Sciences, Università della Tuscia, Viterbo, Italy

Background/Question/Methods
Aposematism is a widespread anti-predatory strategy. It consists of displaying striking behaviors, chromatic signals, odors or sounds, to warn predators about prey toxicity or unpalatability. Although inter-individual variation in aposematic traits has long been considered counter-adaptive, polymorphisms in the chromatic component of warning signals have been widely reported among aposematic organisms. Yet, the occurrence of polymorphisms in behavioral traits associated with warning signals is still almost unexplored. Here, we investigate the inter-individual variation in behavioral aposematic displays by focusing on a deimatic behavior performed by several amphibians, the unken-reflex. It consists of a sudden contraction of dorsal muscles, leading the individual to arch the body and expose vividly colored body parts. We aimed to address the following questions: (i) is the unken-reflex a polymorphic and repeatable behavior? (ii) does this variation relate to personality traits? To answer these questions, we sampled individuals of the yellow-bellied toad Bombina pachypus – a textbook example of unken-reflex - and scored multiple components of their startling behavior and individual personality in a series of common-garden experiments.
Results/Conclusions
We found that, even under repeated stimulation, only about half of the individuals of B. pachypus exhibited unken-reflex behavior. We also found substantial inter-individual variation in the intensity of the unken-reflex. Furthermore, individual responses to the stimuli were highly consistent over multiple trials (all intraclass correlation coefficients > 0.5; P<0.01). Moreover, we found a significant association (P<0.05) between components of the unken-reflex behavior and inter-individual differences along the shy-bold axis of personality. Such an unexpected level of intraspecific behavioral variation raises intriguing questions related to the adaptive processes maintaining polymorphisms in aposematic traits, amenable to further investigation.