Meeting Abstract
Species of terrestrial ectotherms such as lizards, with relatively large latitudinal geographic ranges, are subject to spatially varied climatic conditions. At the geographic extremes, lizards may be challenged frequently by environmental temperatures that are either too warm or too cool for effective thermoregulation during the daily activity period. Lizards challenged thermally must either be inactive or accept suboptimal body temperatures (Tb) when active. We documented Tb of field-active (TbF) Sceloporus occidentalis from three distinct climate zones in Washington State (the species’ northern geographic extreme). We also measured preferred Tb of lizards in a laboratory thermal gradient (TbL), where precise thermoregulation is easily achievable. In the warmest of the three climate zones, in south-central Washington where the daily mean maximum air temperature in mid-summer was 38.9°C (too warm for lizard activity), the mean TbF of lizards was 35.9°C. These temperatures were significantly higher than those in the cool coastal climate, where mean daily maximum air temperature in mid-summer was 27.7°C (rarely too warm for lizard activity) and mean TbF was 35.4°C. Furthermore, from the warm climate, distribution of lizard TbF skewed warmer than TbL. In contrast, TbF of lizards from the coast skewed cooler than the TbL. We infer that field-active lizards from the warmer inland sites of Washington often must accept Tb near the upper limit of their preferred Tb range (36°C), and expect that body temperatures of field-active S. occidentalis to the south also skew high. Inexplicably, lizards from the intermediate climate zone (daily mean maximum air temperature in mid-summer of 33°C) exhibited significantly warmer TbL than those from the other two sites despite achieving similar TbF.
