Habitat dependent effects of experimental immune challenge on lizard anti-predator responses

Abstract: Lizards often respond to predators by hiding in sunless refuges, but this eliminates opportunities for thermoregulatory basking. Hiding can therefore lower body condition. Furthermore, in ectotherms basking is important to induce fever and activate an immune response. A potential trade-off therefore exists between lowering predation risk and elevating body temperature to fight infection. Such a trade-off could be habitat dependent if habitats differ in the relative risk of predation versus that of acquiring or countering an infection. Here we take an experimental approach to test whether lizard basking behavior is affected by a trade-off between predator avoidance and fighting an infection. We quantified the anti-predator behavior of male lizards (Podarcis liolepis) both before and after they were immune challenged (injected with LPS) or not (injected with PBS control). To test the generality of any trade-off, we tested lizards from both an urban and a natural habitat. We found that males spent less time hiding following a simulated predator attack after they had been immune challenged than before, but this decline was only significant for males from the natural habitat. We also tested whether morphological traits, body condition, and immune response level explained variation in male hiding time. In the natural habitat, but not in the urban habitat, males with relatively small heads hid for significantly longer. In conclusion, we show that lizard anti-predator behavior is affected by an immune challenge. Habitat differences in the factors that predict hiding time offers potential insights into why this might be the case. Significance statement: There is a potential trade-off for ectotherms between remaining in a place protected from predators and countering an immune challenge. This is because hiding in sunless refuges eliminates opportunities for thermoregulatory basking that induce a fever. The optimal response to this trade-off might change depending on the habitat. Here, we compare the hiding behavior of males from natural and urban habitat following an experimental immune challenge. We found that the hiding time of immune-challenged males decreased but only for those from the natural habitat.