Thermal constraints of refuge use by Schreiber's green lizards, Lacerta schreiberi (original) (raw)
Related papers
Experimental manipulation reveals the importance of refuge habitat temperature selected by lizards
Austral Ecology, 2010
Refuges provide shelter from predators, and protection from exposure to the elements, as well as other fitness benefits to animals that use them. In ectotherms, thermal benefits may be a critical aspect of refuges. We investigated microhabitat characteristics of refuges selected by a heliothermic scincid lizard, Carlia rubrigularis, which uses rainforest edges as habitat. We approached lizards in the field, simulating a predator attack, and quantified the refuge type used, and effect of environmental temperatures (air temperature, substrate temperature and refuge substrate temperature) on the amount of time skinks remained in refuges after hiding (emergence time). In respone to our approach, lizards were most likely to flee into leaf litter, rather than into rocks or woody debris, and emergence time was dependent on refuge substrate temperature, and on refuge substrate temperature relative to substrate temperature outside the refuge. Lizards remained for longer periods in warmer refuges, and in refuges that were similar in temperature to outside.We examined lizard refuge choice in response to temperature and substrate type in large, semi-natural outdoor enclosures. We experimentally manipulated refuge habitat temperature available to lizards, and offered them equal areas of leaf litter, woody debris and rocks. When refuge habitat temperature was unmanipulated, lizards (85%) preferred leaf litter, as they did in the field. However, when we experimentally manipulated the temperature of the leaf litter by shading, most skinks (75%) changed their preferred refuge habitat from leaf litter to woody debris or rocks. These results suggest that temperature is a critical determinant of refuge habitat choice for these diurnal ectotherms, both when fleeing from predators and when selecting daytime retreats.
Fight versus flight: Body temperature influences defensive responses of lizards
Animal Behaviour, 1982
In laboratory studies we determined that the defensive responses used by two agamid lizards, Agama savignyi and A, pallida, change as a function of body temperature. At high body temperatures, these lizards flee rapidly from predators. At lower body temperatures, which reduce sprint speed, the lizards rarely run but instead hold their ground and attack aggressively. This temperaturedependent switch in defensive behaviour may have evolved because cold lizards that live in open habitats would have little chance of outrunning predators. Defensive behaviours of animals may in general be sensitive to physiological variables that influence locomotor performance.
Acta Amazonica
In ectotherms, defensive responses to predators usually depend on cost-benefit relationships between death risk and the energy required to flee. In this study we investigate Amazonian lizards to test the hypothesis that the minimum predator approach distance (PAD) is influenced by temperature and camouflage. We test the hypothesis that PAD estimated for species with different thermoregulation modes respond differently to temperature and camouflage. We sampled 35 lizards of a heliotherm and a non-heliotherm species, for which we simulated a terrestrial visually oriented predator. Using a fixed-effects linear model, temperature positively affected PAD estimates, but the camouflage did not contribute to the model. Using a mixed linear model assuming thermoregulation mode as a random factor, camouflage negatively affected PAD estimates, independently of temperature. Our findings suggest that high exposure to predators in open habitats may be compensated by rapid fleeing optimized by hig...
Ectotherm antipredator behaviour might be strongly affected both by body temperature and size: when environmental temperatures do not favour maximal locomotor performance, large individuals may confront predators, whereas small animals may flee, simply because they have no other option. However, integration of body size and temperature effects is rarely approached in the study of antipredator behaviour in vertebrate ectotherms. In the present study we investigated whether temperature affects antipredator responses of tegu lizards, Tupinambis merianae, with distinct body sizes, testing the hypothesis that small tegus (juveniles) run away from predators regardless of the environmental temperature, because defensive aggression may not be an effective predator deterrent, whereas adults, which are larger, use aggressive defence at low temperatures, when running performance might be suboptimal. We recorded responses of juvenile (¼ small) and adult (¼ large) tegu lizards to a simulated predatory attack at five environmental temperatures in the laboratory. Most differences between the two size classes were observed at low temperatures: large tegus were more aggressive overall than were small tegus at all temperatures tested, but at lower temperatures, the small lizards often used escape responses whereas the large ones either adopted a defensive posture or remained inactive. These results provide strong evidence that body size and temperature affect the antipredator responses of vertebrate ectotherms. We discuss the complex and intricate network of evolutionary and ecological parameters that are likely to be involved in the evolution of such interactions.
Oecologia, 2008
) cost-benefit model of lizard thermoregulation predicts variation in thermoregulatory strategies (from active thermoregulation to thermoconformity) with respect to the costs and benefits of the thermoregulatory behaviour and the thermal quality of the environment. Although this framework has been widely employed in correlative field studies, experimental tests aiming to evaluate the model are scarce. We conducted laboratory experiments to see whether the common lizard Zootoca vivipara, an active and effective thermoregulator in the field, can alter its thermoregulatory behaviour in response to differences in perceived predation risk and food supply in a constant thermal environment. Predation risk and food supply were represented by chemical cues of a sympatric snake predator and the lizards' food in the laboratory, respectively. We also compared males and postpartum females, which have different preferred or ''target'' body temperatures. Both sexes thermoregulated actively in all treatments. We detected sex-specific differences in the way lizards adjusted their accuracy of thermoregulation to the treatments: males were less accurate in the predation treatment, while no such effects were detected in females. Neither sex reacted to the food treatment. With regard to the two main types of thermoregulatory behaviour (activity and microhabitat selection), the treatments had no significant effects. However, postpartum females were more active than males in all treatments. Our results further stress that increasing physiological performance by active thermoregulation has high priority in lizard behaviour, but also shows that lizards can indeed shift their accuracy of thermoregulation in response to costs with possible immediate negative fitness effects (i.e. predation-caused mortality).
Refuge Use in a Patagonian Nocturnal Lizard, Homonota darwini: The Role of Temperature
Journal of Herpetology, 2010
The thermal quality of diurnal refuges is important to the performance and survival of nocturnal reptiles. We studied refuge use on both slopes of an east-west-oriented hill by the thigmothermic gecko Homonota darwini, the southernmost-distributed nocturnal lizard in the world, in the vicinity of Bariloche, Rio Negro, in the Patagonia of Argentina. Because of the harsh climatic conditions in Patagonia, suitable refuges are limited, and retreat-site use is important for these geckos. Homonota darwini used refuges significantly more frequently on the warmer western slope in our study site. Geckos on the western slope used those refuges with higher temperatures regardless of size and thickness of rocks that acted as retreats. We tested whether refuge temperature affected locomotor performance of these lizards. Performance experiments showed that maximum sprint speed was affected by the temperature of the refuges. Refuges at 22.5uC allowed lizards to achieve their fastest sprint performance. Unexpectedly, sprint performance of lizards that used refuges with temperatures .32uC was the lowest among all tested refuge temperatures (18u, 22.5u, 27.5u, and 33uC). Our data illustrate the importance of the thermal quality of refuges for reptiles living in extreme environments. 2
Canadian Journal of Zoology, 2002
Behavioural regulation of body temperature in thermally heterogeneous habitats requires different amounts of time that could otherwise be dedicated to foraging and social activities. In this study I examined how four populations of the lizard Zootoca vivipara along an altitudinal gradient (250-1450 m) adjust their thermal-physiology traits and thermoregulatory behaviour to compensate for increasing time costs of thermoregulation. I focused on variation in several physiological (set-point temperature, heating rate) and behavioural traits (microhabitat selection, basking frequency, extent of thermoregulation). To estimate potential time spent basking and foraging by lizards that were not employing any behavioural compensatory mechanism, I used a simple biophysical model of thermoregulation, including information about operative temperatures at the study sites, selected temperature range, and heating/cooling rates. Time costs of thermoregulation for each population were calculated as p...
Journal of Thermal Biology, 2007
1. An organism's thermal tolerance to the environment may indicate a thermal limit to its geographical distribution. 2. We measured the lower critical minimum (CTMin) and lower lethal temperature in the lizard Pseudocordylus melanotus melanotus. 3. CTMin was 10.1770.48 1C and the lower lethal temperature was À5.1570.31 1C. 4. All lizards that froze did not survive. This suggests that these lizards are restricted to areas where the microclimate allows them to avoid freezing. 5. Pseudocordylus m. melanotus can allow their body temperatures to drop well below CTMin without any ill effect.
Correlated evolution of thermal characteristics and foraging strategy in lacertid lizards
Journal of Thermal Biology, 2007
1. We investigated the association between field body temperatures (T b), field air temperatures (T a), and their differences (D) with measurements of foraging activity (percentage of time moving (PTM), number of movements per minute (MPM) and proportion of prey attacked while moving (PAM)) for 25 species of lacertid lizards. 2. Lizards active at relatively high field body temperatures tended to have higher PTM and PAM values. We found no association between temperatures and MPM. The difference D did not co-vary with PTM and MPM, but showed a positive trend with PAM. 3. Our results seem robust with regard to the assumptions of different models of evolution and to the phylogenetic trees used.