Prey often respond to predator presence by increasing their use of refuges. However, unfavorable thermal conditions in refuges might entail physiological costs for an ectothermic prey. Thus, the decision of when to come out from a refuge should be optimized by considering the expected fitness effects of diminution of predation risk with time, but also by considering the cost of the loss of time spent at optimal body temperature maximizing physiological functions. The model of Ydenberg and Dill describes the trade-off between risk and cost for a prey fleeing to a refuge. We present a special case of this model to predict how emergence time from the refuge in lizards or other ectotherms should vary as a function of risk of predation and thermal costs of refuge use. The analyses of the variation in emergence time from a refuge of Lacerta monticola lizards in the field under two different predation risk levels supported the predictions of the model. As predicted, time spent in the refuge was longer when the threat of the initial attack had been higher, and therefore the subsequent diminution of risk was slower, but only when lizards emerged at the same place where they hid. When initial body temperature was high, some lizards decreased emergence time by emerging from a different place. In addition, the effects of thermal costs were more relevant in the high-risk situation. Time spent in the refuge under high risk increased when thermal conditions of the refuge were more similar to thermal conditions outside (i.e., physiological costs of refuge use were lower). We conclude that optimization of refuge-use strategies might help lizards cope with changes in predation risk without incurring excessive physiological costs.

According to current evolutionary theory, advertising traits that honestly indicate an organism's genetic quality might be costly to produce or maintain, though the kind of costs involved in this process are controversial. Recently the immunocompetence hypothesis has proposed that testosterone (T) stimulates the expression of male sexually selected traits while decreasing immunocompetence. Even though some recent studies have shown an effect of T on ectoparasite load, the dual effect of the hormone has not been addressed in free-living populations. Here we report results of an experiment in a free-living population of the lizard Psammodromus algirus during the mating season. Males implanted with T had larger patches of breeding color and behaved more aggressively than control males. In T-implanted males, the increase in number of ticks during the mating season was significantly higher than in control males and this negatively affected several hematological parameters. T-males suffered significantly higher mortality than control males during the experiment The results from the manipulation of T are consistent with the dual effect of this hormone.

Little is known about the factors causing variation in behavioural plasticity and the interplay between personality and plasticity. Habituation to predators is a special case of behavioural plasticity. We investigated the direct and indirect effects of boldness, exploration and sociability traits on the habituation ability of Iberian wall lizards, considering exposure and sex effects. Individual boldness was consistent across several non-habituation contexts, but it did not significantly affect habituation. Exploration had a strong direct effect on habituation, with more exploratory individuals being able to habituate faster than less exploratory ones, probably because of their ability to assess risk better. Individual variation in habituation was also affected by sociability, but this was an indirect effect mediated by exposure to the predator. Less social individuals avoided refuges with conspecific cues, increasing exposure to the predator and eventually habituation. Finally, the direct effects of sex (females habituated faster than males) were opposite to its indirect effects through exposure. We conclude that risk assessment, instead of the proactivity–reactivity gradient usually considered in the literature, can affect behavioural plasticity through complex interactions between direct and indirect effects, including exploratory behaviour, degree of exposure to the predator and sex, which represent novel mechanisms generating inter-individual variation in plasticity.

Research on fluctuating asymmetry (FA)–mediated sexual selection has focused almost exclusively on visual signals and ignored chemical communication despite the fact that many species rely on chemical signals for attracting mates. Female mate choice based on visual traits appears to be rare in lizards. However, the femoral glands of male lizards produce pheromones which might transmit chemical information about an individual's developmental stability. Therefore, we hypothesized that mate choice may be based on chemical cues. We analysed the effect of the developmental stability levels of males on the attractiveness of males' scents to females in a laboratory experiment with the lizard Lacerta monticola. When we offered two males of similar body size, females preferentially associated with the scents of males with low FA in their femoral pores and also with the scents of males with a higher number of femoral pores. This suggested that the females were able to discriminate the FA of the males by chemical signals alone and that the females preferred to be in areas marked by males of high quality, thus increasing their opportunities of mating with males of high quality. We suggest that the quality and/or amount of male pheromones could communicate the heritable genetic quality of a male to the female and thereby serve as the basis for adaptive female choice in lizards.