The relationships between toad behaviour, antipredator defences, and spatial and sexual variation in predation pressure

Abstract

Background Animal behaviour is under strong selection. Selection on behaviour, however, might not act in isolation from other fitness-related traits. Since predators represent outstanding selective forces, animal behaviour could covary with antipredator defences, such that individuals better suited against predators could afford facing the costs of riskier behaviours. Moreover, not all individuals undergo equivalent degrees of predation pressure, which can vary across sexes or habitats. Individuals under lower predation pressure might also exhibit riskier behaviours. Methods In this work, I tested these hypotheses on natterjack toads (Epidalea calamita). Specifically, I gauged activity time, exploratory behaviour and boldness in standard laboratory conditions, and assessed whether they correlated with body size and antipredator strategies, namely sprint speed, parotoid gland area and parotoid gland colour contrast. Additionally, I compared these traits between sexes and individuals from an agrosystem and pine grove, since there is evidence that males and agrosystem individuals are subjected to greater predation pressure. Results Sprint speed as well as parotoid gland contrast and size appeared unrelated to the behavioural traits studied. In turn, body mass was negatively related to activity time, boldness and exploration. This trend is consistent with the fact that larger toads could be more detectable to their predators, which are mostly gape unconstrained and could easily consume them. As predicted, females exhibited riskier behaviours. Nonetheless, agrosystem toads did not differ from pine grove toads in the behavioural traits measured, despite being under stronger predation pressure.

Larval newts from turbid and transparent waterbodies exhibit different morphological and behavioural traits

“…Larvae were released at the centre of the arena. Two minutes of habituation were allowed, after which the activity of the larvae was recorded for 10 min (Chajma et al, 2020; Zamora‐Camacho, 2022).…”

“…Several behavioural variables were analysed from the videos using the software Tracker v.4.92. Firstly, activity time was measured as the amount of time the larvae spent moving (Chajma et al, 2020; Zamora‐Camacho, 2022). We also estimated exploratory behaviour as the number of different squares visited (Chajma et al, 2020; Zamora‐Camacho, 2022) and as the total number of squares visited (including repeated visits; Carlson & Langkilde, 2013; Zamora‐Camacho, 2022).…”

“…Firstly, activity time was measured as the amount of time the larvae spent moving (Chajma et al, 2020; Zamora‐Camacho, 2022). We also estimated exploratory behaviour as the number of different squares visited (Chajma et al, 2020; Zamora‐Camacho, 2022) and as the total number of squares visited (including repeated visits; Carlson & Langkilde, 2013; Zamora‐Camacho, 2022). The former variable assumes that the individual can distinguish and keep track of zones visited previously visited, whereas the latter does not (Carlson & Langkilde, 2013).…”

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

“…For instance, locomotor performance can be tuned to habitat differences in predator abundance (Fu et al, 2013). Likewise, sex differences in exposure might explain why males of some species tend to be better suited against predators (Zamora‐Camacho, 2022a).…”