Assessment of the health status of a reintroduced headstarted population of Emys orbicularis galloitalica through the analysis of weight and size growth curves and allometries

Biometric measures can serve as proxies for the health condition of wildlife populations, and deviations from their expected trends may signal stress, disease, or resource scarcity. This study evaluates the success of the reintroduction of a headstarted European pond turtle population by analysing individual growth rates and allometries. From 2016 to 2018, three groups of turtles that had experienced two different captive-rearing protocols were released, totalling 32 individuals. To collect biometric data, eight capture sessions were conducted from 2017 to 2022. Twenty-nine out of 32 individuals were recaptured, with 17 identified as males and 9 as females. The first group, which hibernated during the winter before release, was smaller and lighter at release but grew faster than the other two, which avoided hibernation; in addition, we found a significant difference in the allometric relationship between weight and carapace length when comparing the first group with the other two, due to a sex-dependent differential weight gain among groups. Despite limitations related to sample size and imbalance issues, we found evidence suggesting that the successful reintroduction of multiple stocks of individuals released at different times may be attributable to the simultaneous action of the rearing strategy and the intraspecific within-sex competition for food or space.