Incubation and Overwintering Conditions Influence Righting Performance of Hatchling Turtles

Abstract

Conditions experienced during early life stages may influence an array of fitness-relevant phenotypes, especially in oviparous ectotherms. The pond slider (Trachemys scripta) has two life stages particularly vulnerable to the influence of ambient conditions: the egg stage and hatchling overwintering stage. We aimed to determine the influence of both incubation temperature and overwinter environment on hatchling turtle performance. In 2019 and 2020, we incubated pond slider eggs at five constant temperatures (24°C, 26°C, 28°C, 30°C, 32°C). After hatching, turtles were distributed to two housing treatments that simulated overwintering in a terrestrial nest or an aquatic environment. In the spring following hatching, we conducted righting response trials, which are frequently used performance measures that may be associated with coordination and neuromuscular function. Our linear mixed-effects models show that incubation temperature, overwinter environment, and their interaction significantly influenced hatchling phenotypes (e.g., shell and tail dimensions, body mass) and righting performance (e.g., total righting response time, latency to right). Aquatically overwintering hatchlings that were incubated at cooler temperatures righted themselves faster than those incubated at warmer temperatures. This relationship did not exist in terrestrially overwintering hatchlings, which had faster overall righting times that were not affected by incubation temperature, suggesting overwintering in the nest may better equip hatchlings for post-emergence dispersals over land.