ABSTRACT Aim Although Bergmann's and Allen's rules are widely recognized, their study in micromammals such as shrews remains scarce. Ecogeographical rules are crucial for anticipating organismal responses to environmental change, as they describe morphological variation across climatic gradients and may offer predictive value under climate change scenarios. This study aims to evaluate whether shrews conform to these rules and to identify the environmental predictors most strongly associated with body size variation. Location Western Palearctic. Time Period Present. Major Taxa Studied Genus Sorex . Methods We use 3D morphological models to examine both rules in European shrews (genus Sorex ) and test two hypotheses that have been suggested as possible explanations (namely, heat conservation and resource rule). Studying both ecogeographical rules from 3D photogrammetry models allows a direct estimation of surface‐volume ratios and hence a more in‐depth assessment of classical thermoregulatory mechanisms than those derived from typically used linear size metrics. Results Our generalized additive models identified the interaction between annual precipitation and NDVI as the most relevant predictor, with higher precipitation and resources associated with larger body size. Conversely, shrews exhibited longer tails in warmer environments, consistent with Allen's rule. Main Conclusions We found no evidence supporting the classical heat conservation hypothesis for Bergmann's rule. Instead, body size variation was primarily linked to water and resource availability, rather than thermal constraints. Conversely, shrews exhibited longer tails in warmer environments, consistent with Allen's heat dissipation mechanism. These findings suggest that Sorex shrews defy both rules to some extent. As micromammals with elevated metabolic rates, reduced thermal inertia, and extremely high water turnover, their morphological variation seems to be strongly determined by food and water availability as well as thermal conditions.
Valle‐Cabo et al. (Fri,) studied this question.