Does background colouration affect the behaviour of tadpoles? An experimental approach with an odonate predator

Predation is a primary driver of tadpole assemblages, and the activity rate is a good predictor of the tadpoles' tolerance for predation risk. The conflicting demands between activity and exposure to predation can generate suboptimal behaviours. Because morphological components, such as body colouration, may affect the activity of tadpoles, we predict that environmental features that enhance or match the tadpole colouration should affect their survival or activity rate in the presence of a predator. We tested this prediction experimentally by assessing the mortality rate of tadpoles of Rhinella schneideri and Eupemphix nattereri and the active time on two artificial background types: one bright-coloured and one black-coloured. We found no difference in tadpole mortality due to the background type. However, R. schneideri tadpoles were more active than E. nattereri tadpoles, and the activity of R. schneideri was reduced less in the presence of the predator than that of E. nattereri. Although the background colouration did not affect the tadpole mortality rate, it was a stimulus that elicited behavioural responses in the tadpoles, leading them to adjust their activity rate to the type of background colour. © 2013 Dipartimento di Biologia, Università degli Studi di Firenze, Italia.

Unpalatability of Hyla semilineata tadpoles (Anura) to captive and free-ranging vertebrate predators

This study examines the unpalatability of Hyla semilineata tadpoles, relating this possible defence mechanism to their black, presumably aposematic, colouration. Bullfrog tadpoles (Rana catesbeiana), similar in size to the H. semilineata larvae, were used as controls in the experiments. The palatability of H. semilineata tadpoles was tested by offering the tadpoles to Fish (Hoplias malabaricus), free-ranging passerine birds (Pitangus sulphuratus) and hawks (Buteo magnirostris), and domestic chickens (Gallus domesticus). All predators showed a significant preference towards the control R. catesbeiana tadpoles. However, in experiments with fish, this preference was not significant for tadpole capture, only for their ingestion, suggesting that the fish could not distinguish between the two species before tasting them. Although great kiskadees (P. sulphuratus) preferred the control R. catesbeiana tadpoles, they promptly ingested more than half of the test H. semilineata tadpoles when these were offered alone. The chickens, used as naive predators, clearly learned to avoid the black H. semilineata tadpoles after a few trials. The conspicuous colouration and unpalatability of H. semilineata tadpoles may benefit the individual as well as the group, depending on the predator involved.

Dois cisnes à procura de um personagem: uma leitura pirandelliana do filme Cisne Negro

Pós-graduação em Letras - FCLAS