Rebouças, R., A. B. Carollo, M. O. Freitas, C. Lambertini, R. M. N. Santos & L. F. Toledo

Is the conspicuous dorsal coloration of the Atlantic forest pumpkin toadlets aposematic? pp. 39-47 plus Supplementary material.

Abstract. While crypsis is the ability of avoiding detection of an animal by another, aposematism refers to the presence of conspicuous or contrasting colour patterns, signalling the unprofitability of a prey to potential predators. Aposematic coloration is meant to advertise that the prey is dangerous in some way, for example by being aggressive, emitting loud screams, or producing toxic skin secretions. Many contrasting and colourful anuran species are considered aposematic. However, despite past studies demonstrating that a conspicuous coloration is an element of aposematism, we still lack experiments to confirm this relationship. Therefore, we conducted experimental assays to test if the fluorescent property and bright colour patterns of Brachycephalus are related to aposematism. We also tested the allochthonous/autochthonous hypothesis, which predicts that local (autochthonous) colour morphs would be more avoided by local predators than allochthonous colour morphs. To this end, we conducted ex situ experiments with B. ephippium individuals (prey) that were housed inside polycarbonate and glass boxes and presented thus to common chickens (predator) to test if their fluorescence improved predation avoidance. In situ experiments were conducted at two Atlantic forest sites, where both cryptic and conspicuously coloured Brachycephalus species occur. Here, we positioned trios of plasticine models, (one brown cryptic model, one yellow, and one red conspicuous model) in two situations: right on the leaf litter and on white cardboard sheets. In our ex situ experiments, we found that fluorescent dorsal colours did not influence predation, as chickens did not avoid B. ephippium even after experiencing their taste. In in situ experiments, we found differences in the rates of predation between cryptic and conspicuous models. In addition, we also obtained data that corroborated the autochthonous/allochthonous hypothesis. Our results support the assumption that the conspicuous coloration of Brachycephalus spp. is aposematic, prevents predation, and that local predator assemblages recognize autochthonous colour morphs.

Key words. Amphibia, Anura, Brachycephalus, aposematism, conspicuousness, coloration, predation, predator-prey interactions.