Do Active and Passive Antipredator Defences in the Toad Epidalea calamita Differ between Males and Females from Natural Habitats and Agrosystems?

Abstract

Due to their assumed costs, simultaneous antipredator strategies are expected to face trade-offs, which, however, could be milder in individuals subjected to a more intense predator pressure. In this work, I studied the relationship between locomotion and parotoid glands in the natterjack toad, Epidalea calamita. Specifically, I predicted that individuals with reduced sprint speed would rely more on their chemical defences, having larger and more aposematically coloured parotoid glands. In addition, I expected this trade-off to be more evident in females and toads from pine grove habitats, because, according to previous work, males and toads from agrosystems are under greater predator pressure. However, sprint speed showed no relationship with coloration, but toads with proportionally greater parotoid glands were also proportionally faster. Thus, the costs of these antipredator traits might not be high enough to make them interfere, or the benefits of simultaneous optimisation of sprint speed and parotoid gland size might outweigh the costs of it in some individuals. In any case, habitat and sex did not affect these relationships, so the trends detected are valid across sexes and the habitats studied.

Contextualising the bizarre: The integrated functioning of rib puncture as an antipredator defence in the Iberian ribbed newt (Pleurodeles waltl)

“…This finding suggests that, rather than being subjected to a trade‐off, these traits can be simultaneously optimised in females. In Epidalea calamita toads, both males and females, locomotor performance, and parotoid gland size were positively correlated, which could indicate that the costs of these defences are not high enough to interfere (Zamora‐Camacho, 2021). In the case of these newts, the fact that males exhibit a faster rib response and, unlike females, those with more warts have also more salient warts, suggests that predation risk is milder in females, as antipredator defences are usually sharper in the sex under greater predation risk, typically males (Grignolio et al, 2018; Meuthen et al, 2018).…”