Trading Heat and Food for Safety: Costs of Predator Avoidance in a Lizard

Abstract

I examined the long-term consequences of a trade-off between predation risk and resource acquisition for the garden skink (Lampropholis guichenoti) by rearing hatchlings to maturity in outdoor enclosures covered with snake predator scent (mimicking high predator densities) or control scent (mimicking low predator densities). Open areas provided optimal foraging and basking sites but were covered with scent, whereas retreat sites provided suboptimal foraging and basking opportunities and were not scented. During the initial six months of the experiment, lizards reared in enclosures covered with scent from a natural predator became active later in the day, showed reduced mobility, and selected “safer” substrate microhabitats than did lizards raised in enclosures covered with control scent. These behavioral shifts reduced opportunities to forage and bask for lizards in the predator-scented enclosures. During the study, however, lizards from predator-scented enclosures became gradually less responsive to snake chemical cues, and after one year there were no differences in the activity patterns and substrate microhabitat use of lizards in both treatments. This pattern of behavior is paralleled by variation in growth rates of lizards. Throughout the study, lizards exposed to predator scent were lighter and shorter than were lizards exposed to control scent. However, this result reflects differential rates of growth by lizards only during the first six months of the experiment. Nevertheless, lizards that grew slowly early in life, as a consequence of predator avoidance, attained smaller body sizes at maturity and produced lighter clutch masses and offspring. Thus, predator avoidance tactics employed early in a lizard's life can impose long-term fitness costs.