Authors: Telea, Alexandra; Vlad, Sabina;Cogălniceanu, Dan;Fănaru, Geanina;Carlsson, Martin;Iosif, Ruben;Drăgan, Ovidiu;Plăiașu, Rodica;Băncilă, Raluca;

Reduction in body size in response to global warming has been widely documented under experimental conditions. However, it is uncertain whether the response extends to wild populations, as it varies across different taxa and is influenced by other variables. We used a data set collected over the span of 16 years (2006-2021), on body sizes (i.e., body length and body mass) of one tortoise and three snake species from southern Danube Delta Biosphere Reserve, Romania. The aim of the study was to examine whether body size changed over time and which climate variables can explain the variation. The results showed a significant increase over time in body length of Dolichophis caspius and Natrix tessellata, while for Testudo graeca it was a statistically nonsignificant increase. Body mass significantly increased over time only in D. caspius and T. graeca. Decrease in body mass was explained by an increase of temperature only in the two Natrix species, while a decrease in body length only in Natrix natrix. Overall, our results suggest that climate warming affects body sizes in reptiles differently and does not support the hypothesis that declining body size as a response to warming is a universal response.