engleski

Natural history of Malagasy poison frogs: experimental analysis of aposematism, morphology of tadpoles, and longevity

Poisonous frogs from genus Mantella belong to the Malagasy-Comoran endemic family Mantellidae and include about 17 species. Here, the tadpole morphology of nine species of Mantella is described and compared. The tadpole morphology of M. crocea/milotympanum-hybrids, M. madagascariensis, M. pulchra, M. viridis, M. baroni, M. bernhardi and M. betsileo is described for the first time. Species identification is difficult only by means of morphometric variables. Longevity of five species of Mantella (M. aurantiaca, M. baroni, M. bernhardi, M. crocea, M. madagascariensis) was examined applying skeletochronology. In 57% of the specimens, no lines of arrested growth (LAGs) were found, and the number of LAGs recognized in the remaining specimens ranged between zero and two. The effectiveness of aposematic colouration in Mantella was tested exposing clay frog models in three different colours to rainforest habitats in Madagascar. Predation observed on models was tested for correlation between colouration of models as a distinctive predictor of predation, time of predation (day, night), shape (frog, shapeless), position of the model and influence of predators’ experience. In addition, learning effect among the predators was studied. Most predictors showed not to be significant determinants of predation. Efficiency in predator deterring based on visual and olfactory cues was tested by feeding choice experiments, with several species of snakes caught in the field in Madagascar. Snakes were offered one Mantella and one edible frog at the same time, giving them the opportunity to choose. Snakes showed a strong preference for edible frogs over specimens of Mantella. I also compared predation rate on two types of frogs among “experienced” (caught in Mantella habitat) and naïve snakes (caught in areas not inhabited with Mantella) and found significant differences, with “experienced” snakes eating altogether only one Mantella frog.

Madagascar; Mantella; Amphibia; skeletochronology

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