Correlated geographic variation in predation risk and antipredator behaviour within a wide‐ranging snake species (Notechis scutatus, Elapidae)

Abstract

Geographic variation in antipredator behaviour within wide-ranging species may be driven by both genetic and environmental influences. We quantified antipredator responses in neonatal (laboratory born, n = 555) and adult (field caught, n = 346) tiger snakes (Notechis scutatus) from 11 mainland and island sites in southern Australia. We used these data to test predictions from Bonnet et al.'s hypothesis that the vigour of antipredator responses in this species reflects behavioural plasticity (in turn, driven by an individual snake's exposure to predators during its lifetime) rather than by genetic variation in this trait. We used the number of predator taxa in each area as an index of predator risk. As predicted, adult snakes from predator-rich areas had more vigorous defensive responses when handled, whereas neonatal behaviour (although also variable among populations) was unrelated to predator species richness. Adult males bit more readily than adult females (as expected from the greater predation exposure of males during mate searching) but no such sex difference was evident in neonates. Although alternative models remain possible, our data are most consistent with the hypothesis that geographic divergence in antipredator tactics within this species primarily reflects developmentally plastic responses to local predation risk.

Historical influence of predation pressure on escape by Podarcis lizards in the Balearic Islands

“…Neither capacity is apparent in P. lilfordi , consistent with historical loss by evolution of island tameness. Whether adjustments to predation pressure reflect solely plastic responses during ontogeny, as suggested for the elapid snake Notechis scutatus (Aubret, Michniewicz & Shine, 2011), evolutionary processes, or both, remains unknown.…”

The sooner the better: reproductive phenology drives ontogenetic trajectories in a temperate squamate (Podarcis muralis)

“…After 1 month of age, we recorded thermal preferences using a thermal gradient (temperature range (2007) (emissivity set at 0.95 and the thermometer was oriented in-line with the lizard's body axis). The next day, we quantified defensive behaviour using a behavioural procedure adapted from Bonnet et al (2005) and Aubret, Michniewicz & Shine (2011). Before the trial, each individual was placed in a temperature-controlled chamber (FOC 225E; Velp Scientifica) set at 30°C for at least 30 min to acclimate to the test temperature.…”

The role of innate and environmental influences in shaping antipredator behavior of mainland and insular gartersnakes (Thamnophis sirtalis)

“…However, despite these mixed results, the traditional view that island populations or species become less fearful on islands based on the idea that there are generally fewer predators in island systems is supported here, as both of the islands in which relaxation of antipredator behavior (Coss 1999) was documented were characterized by fewer potential predators than the islands that did not differ from the mainland populations. However, despite the support the present and previous works (Blazquez et al 1997;Bonnet et al 2005;Aubret et al 2010) provide for the hypothesis that island animals are less reactive than mainland animals, caution should still be taken before applying the island tameness hypothesis broadly, as a variety of factors (both intrinsic and extrinsic) need to be taken into account when examining such geographic variation in behavior. The work presented here also suggests that there may be both innate and environmental forces at work in shaping the behavior exhibited by insular populations.…”

“…While Bonnet et al (2005) and Aubret et al (2010) indicated that the insular tiger snake (Notechis scutatus occidentalis, Elapidae) populations are more placid than mainland populations as the result of phenotypic plasticity, few others have examined the mechanisms behind the changes they see between mainland and insular populations. The data collected for this study suggest that the behavioral differences that were detected are likely the result of both environmental and innate influences, rather than only environmental influences, but the study system used for this study is thousands of years old (Hough 1958), whereas insular tiger snake populations are only a few hundreds of years old.…”