Abstract
Aposematic signals as well as body behaviours may be important anti-predator defences. Species of the genus Melanophryniscus are characterised by having toxic lipophilic alkaloids in the skin and for presenting a red ventral colouration, which can be observed when they perform the behaviour called the unken reflex. Both the reflex behaviour and the colouration pattern are described as defence mechanisms. However, there are currently no studies testing their effectiveness against predators. This study aimed to test experimentally if both ventral conspicuous colouration and the unken reflex in Melanophryniscus cambaraensis function as aposematic signals against visually oriented predators (birds). We simulated the species studied using three different clay toad models as follows: (a) in a normal position with green coloured bodies, (b) in the unken reflex position with green coloured body and extremities and (c) in the unken reflex position with a green body and red extremities. Models were distributed on a known M. cambaraensis breeding site and in the adjacent forest. More than half of the attacks on the models were from birds; however, there was no preference for any model type. Thus, just the presence of the red colour associated with the motionless unken reflex position does not seem to prevent attacks from potential predators. It is possible that the effective aposematic signal in Melanophryniscus is achieved through the unken reflex movement together with the subsequent exhibition of the warning colouration and the secretion of toxins.
Highlights
IntroductionAntipredator strategies encompass several mechanisms involving the behaviour, morphology and colouration of prey species, which evolve either to avoid detection (e.g. camouflage) or to enhance honest or dishonest unprofitability signaling (e.g. aposematism, masquerade, pursuit deterrence, deflection, and deimatism) [1,2]
Antipredator strategies encompass several mechanisms involving the behaviour, morphology and colouration of prey species, which evolve either to avoid detection or to enhance honest or dishonest unprofitability signaling [1,2]
Melanophryniscus cambaraensis Braun & Braun, 1979 (Fig 1A and 1B) is one of the three species of the genus Melanophryniscus with green dorsal colouration, and with ventral colouration which may vary from red to orange [51,52,53]
Summary
Antipredator strategies encompass several mechanisms involving the behaviour, morphology and colouration of prey species, which evolve either to avoid detection (e.g. camouflage) or to enhance honest or dishonest unprofitability signaling (e.g. aposematism, masquerade, pursuit deterrence, deflection, and deimatism) [1,2]. Unken reflex and aposematic colouration efficiency against bird predation ufrgs.br/ppgban) and Fundacão Zoobotanica do Rio Grande do Sul (http://www.fzb.rs.gov.br/). Attack rate = attack by birds/total of category. When missing models were included as predation attempts, the interaction of model category and background was not significant (χ2 = 1.00; p = 0.61). The type of background was a predictor of bird predation (χ2 = 4.07; p = 0.04), showing that toads on the leaf litter were on average 1,7 times more likely to be attacked than models placed on the white board. Arthropods and unidentified predators were responsible for 7.7%, 6.6% and 32.2% of the total attacks, respectively. Only five out of 90 models were attacked on the breeding site, two by mammals and three by arthropods
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