Ectothermic organisms, such as reptiles, amphibians, and most invertebrates, are unable to produce sufficient metabolic heat to regulate their internal temperature and therefore depend on external heat sources to achieve the body temperatures (T_b) required to sustain their physiological, ecological, and behavioral processes (Vitt and Caldwell 2014; Reppa et al. 2023). The strategies that ectotherms employ to cope with environmental thermal variability fall along a continuum between two extremes: thermoconformers, whose body temperature closely tracks the temperature of their immediate environment, and thermoregulators, which actively maintain T_b within a narrower preferred range by exploiting spatial and temporal thermal heterogeneity through behavioral and, to a lesser extent, physiological mechanisms (Hertz et al. 1993; Bakken and Angilletta Jr 2014). Distinguishing between these strategies is fundamental to understanding the thermal ecology of a species and its potential vulnerability to climate change.

During thermoregulation, lizards exploit several heat sources that operate through distinct physical pathways. Solar radiation, high-energy radiation in the ultraviolet, visible, and shortwave-infrared spectra (≈290–3000 nm), is generally considered the primary heat source for diurnal lizards and is transferred by radiation (Gans 1982; Vitt and Caldwell 2014). Substrate temperature (T_s, also denoted T_substrate) is the temperature of the soil, rock, sand, or leaf litter with which the lizard is in direct contact and transfers heat by conduction (Bakken 1992; Crawford et al. 1983; Menezes and Rocha 2011; Bonavita et al. 2025). Air temperature (T_a) is the temperature of the surrounding medium measured outside the animal’s thermal and hydrodynamic boundary layers and influences T_b mainly through convective exchange (Gans 1982; IUPSThermalCommission 2001; Hertz et al. 1993). Lizards that raise T_b primarily by basking in direct sunlight are classified as heliotherms, whereas those that rely mainly on conductive exchange with warm substrates are classified as thigmotherms (Gans 1982; Şahin and Kuyucu 2021; Dıblan et al. 2026). Many species, in fact, combine both strategies, and wind can further modify heat balance by enhancing convective heat loss when T_b exceeds T_a (Villavicencio et al. 2007; Virens and Cree 2022).

Because these heat sources vary at very fine spatial scales, macroclimatic data (e.g., weather-station air temperatures or gridded climate surfaces such as WorldClim) are often poor proxies for the temperatures actually experienced by ectotherms (Bakken and Angilletta Jr 2014; Lembrechts and Lenoir 2020; Sears and Angilletta Jr 2015; Sears et al. 2016). Vegetation cover, rock crevices, orientation, slope, and substrate type create fine-scale thermal mosaics that provide opportunities for behavioral thermoregulation (Adolph and Porter 1993; Díaz 1997; Li et al. 2017). By selecting favorable microhabitats, lizards can maintain T_b near their preferred range even when macroclimatic conditions would predict otherwise—a phenomenon known as the Bogert effect, in which behavioral buffering of the thermal environment may slow the pace of physiological evolution and mask the climatic vulnerability of a species (Logan et al. 2019). Assessing the thermal biology of ectotherms therefore requires measurements at the microhabitat scale, integrating T_s, T_a, solar radiation, and wind.

The Anatolian rock lizard, Anatololacerta anatolica (Werner 1902), is a small diurnal lacertid endemic to western Anatolia, distributed from north of the Büyük Menderes River to Bursa in the northwest and extending eastward into Central Anatolia at elevations up to ~1,600 m (Karakasi et al. 2021; Şahin et al. 2022). Two subspecies are currently recognized, of which A. a. anatolica occurs in northwestern Anatolia, including Mount Spil (Oğuz 2020). The species typically inhabits rocky areas with dense vegetation and proximity to moisture and is frequently found under stones at ambient temperatures of 25–30 °C (Oğuz 2020). Previous work has reported a preferred T_b of approximately 34.5 °C in adults (Oğuz 2020), but data on how individuals in natural populations integrate solar radiation, substrate temperature, air temperature, and wind at the microhabitat scale remain scarce. Potential threats include habitat loss, disturbance of rock shelters, and, notably, climate change: bioclimatic modeling predicts a northward contraction of suitable habitat for the genus under future climate scenarios (Bozkurt 2022; Oğuz 2020; Şahin et al. 2022). Understanding whether A. anatolica is a thermoconformer or a thermoregulator, and whether it relies mainly on heliothermy or thigmothermy, is therefore essential for realistic projections of its climatic sensitivity.

The primary objective of this study is to quantify the relationship between T_b and the microhabitat-scale thermal variables T_s, T_a, solar radiation, and wind speed in Anatololacerta anatolica from Mount Spil (Manisa, western Anatolia). Specifically, this study aims to (i) determine whether the population behaves as a thermoconformer or an active thermoregulator, (ii) identify whether it relies predominantly on heliothermic or thigmothermic heat acquisition, (iii) evaluate potential sex differences in thermal parameters, and (iv) evaluate the direction and magnitude of the influence exerted by each environmental variable on T_b. The findings are intended to contribute to the characterization of the species’ thermal niche and to provide a baseline for assessing its potential vulnerability to future environmental change.

The results show that, in the Mount Spil population of Anatololacerta anatolica, _Tb is significantly associated with microhabitat-scale thermal variables, with T_s and solar radiation emerging as the strongest predictors. Mean T_b (32.32 ± 4.53 °C) was significantly higher than both mean T_s (30.6 ± 6.97 °C) and mean T_a (28.1 ± 4.04 °C), indicating that the population is an active thermoregulator rather than a passive thermoconformer. The right-skewed distribution of T_b–T_s differences (Fig. 1) is consistent with active microhabitat selection rather than complete thermal equilibrium with the environment, in line with Hertz et al. (1993). Similar patterns—mean T_b statistically higher than T_s and T_a—have been reported in Lacerta trilineata and Lacerta viridis (Vacheva et al. 2025), Phymaturus spp. (Alés et al. 2017; Vicenzi et al. 2017), Leiocephalus schreibersi (Marcellini and Jenssen 1989), and Liolaemus spp. (Valdez Ovallez et al. 2023), where such differences have been attributed to basking and substrate-based heat gain.

The mean field T_b recorded in the present study (32.32 ± 4.53 °C) (Suppl. material 2: table SS1) falls slightly below the preferred body temperature (Tpref ≈ 34.5 °C) reported for this species under laboratory conditions (Oğuz 2020). This discrepancy is not unexpected, as field T_b integrates periods of inactivity, movement, and thermal transition that a laboratory-derived set-point temperature does not capture (Hertz et al. 1993). Similar offsets between field T_b and laboratory T_pref have been documented in other lacertid species (Aguado and Braña 2014; Zamora-Camacho et al. 2016), and their magnitude is commonly used as a proxy for the costs and precision of thermoregulation. To our knowledge, comparable field body temperature data for other Anatololacerta species are not yet available in the published literature, which limits direct intergeneric comparisons within the genus. These results are therefore situated in the broader context of sympatric western Anatolian lacertids (Şahin and Kuyucu 2021), which show broadly similar patterns of microhabitat-driven thermoregulation.

Although the Pearson correlation between T_b and T_s was slightly stronger than that between T_b and solar radiation, A. anatolica behaves primarily as a heliothermic—rather than a purely thigmothermic—species for several complementary reasons. First, mean T_b was significantly higher than mean T_s, so individuals are not simply equilibrating with the substrate, as would be expected of a strict thigmotherm; the T_b–T_s correlation rather reflects the fact that solar-heated substrates and basking individuals share the same radiative forcing. Second, in the multiple regression, both T_s and solar radiation remained significant, independent positive predictors of T_b (Table 1), showing that solar radiation contributes to T_b over and above T_s. Third, sun-exposed substrates are themselves heated largely by incoming solar radiation, so T_s carries a strong radiative signal; the fact that T_s, T_a and solar radiation load together on PC1 (Suppl. material 2: table S4) is consistent with this interpretation. The species is therefore best described as combining heliothermy with a component of thigmothermy, with solar radiation acting as the ultimate heat source (Gans 1982; Şahin and Kuyucu 2021).

Regression analyses further indicate that A. anatolica tracks microhabitat thermal heterogeneity rather than relying on macroclimatic averages. This is consistent with growing evidence that macroclimatic data are often inadequate proxies of the temperatures actually experienced by ectotherms (Bakken and Angilletta Jr 2014; Lembrechts and Lenoir 2020; Nordberg and Schwarzkopf 2019; Sears and Angilletta Jr 2015; Sears et al. 2016). Microhabitat heterogeneity provided by rock outcrops and vegetation on Mount Spil likely buffers individuals against extremes in T_a, in line with the Bogert effect—behavioral thermoregulation that partly decouples T_b from macroclimate and may mask genuine physiological vulnerability (Logan et al. 2019). Several studies have shown that lizards in high-altitude or thermally variable environments can maintain T_b well above T_a by exploiting solar radiation (Brewster and Beaupre 2019; Ortega and Martin-Vallejo 2019; Sunday et al. 2014).

The positive, independent effects of T_s and solar radiation on T_b indicate that individuals exploit local thermal opportunities efficiently. Nevertheless, the relatively small mean T_b–T_s difference (1.76 °C; d = 0.27) suggests that, although the difference is statistically significant, its biological magnitude is modest and the species interacts closely with the thermal properties of its immediate substrate, consistent with the moderate thermoregulatory strategies reported by Bonavita et al. (2025).

The PCA results show that T_b, T_s, solar radiation, and T_a load together on PC1, whereas wind speed loads almost exclusively on an orthogonal PC2. This pattern is consistent with previous work emphasizing the dominant, integrated role of radiative and substrate thermal variables in shaping ectotherm thermal ecology (Crawford et al. 1983; Paranjpe et al. 2014) and also with field studies in which wind is reported to influence operative temperature models but is frequently a secondary determinant of T_b (Almeida-Santos et al. 2015; Bakken 1992; Dzialowski 2005; Şahin and Kuyucu 2021). The loading of wind on an axis independent of the radiative–thermal gradient, together with its nonsignificant effect in the multiple regression, suggests that A. anatolica buffers convective cooling through microhabitat selection—use of rock crevices and the base of vegetation—while managing its thermal balance primarily via solar radiation and substrate temperature. Future studies incorporating Hertz et al.’s (1993) thermoregulatory effectiveness index (E), which requires both laboratory-derived preferred temperature ranges and field-deployed operative temperature models, would allow a formal quantification of thermoregulatory precision in this population.

Females maintained significantly higher field T_b than males, despite the absence of detectable differences in body size. Consistent with this, neither SVL nor body mass predicted field T_b in adult individuals, making a thermal inertia explanation unlikely. Sex-specific differences in field T_b are not uncommon among lacertid lizards and are frequently linked to the elevated thermoregulatory demands of vitellogenesis and gestation, during which females may actively seek warmer microhabitats to accelerate embryonic development (Kechnebbou et al. 2025; Vacheva et al. 2025). The moderate effect size suggests that, while the difference is statistically detectable, individual variation in thermoregulatory behavior remains considerable in both sexes. Full quantification of thermoregulatory effectiveness on Mount Spil will require complementary laboratory and operative-temperature data, which are identified as a priority for future work.

The Mount Spil population of Anatololacerta anatolica behaves as an active thermoregulator, maintaining T_b (32.32 ± 4.53 °C) significantly above both T_s and T_a. Multiple regression identified T_s and solar radiation as the only independent, significant positive predictors of T_b, while wind speed was statistically decoupled from the radiative–thermal system. The species combines heliothermy with a component of thigmothermy and buffers convective cooling through microhabitat selection, consistent with the Bogert effect. Females maintained significantly higher field T_b than males, independent of body size, suggesting sex-specific differences in thermoregulatory behavior or microhabitat use that warrant further investigation. These results highlight the importance of microhabitat-scale thermal heterogeneity and thermal refugia for the persistence of A. anatolica and emphasize that climate-change assessments based solely on macroclimatic air temperature are likely to underestimate its vulnerability. Estimation of preferred and operative temperatures in future studies will allow a formal quantification of thermoregulatory effectiveness and refine projections under climate change.