Meeting Abstract
P2.129 Friday, Jan. 4 Cold hardiness influences life history traits of northern turtles: variation in the timing and synchrony of hatchling emergence from the nest BAKER, PJ*; COSTANZO , JP; IVERSON, JB; LEE, RE; Miami University; Miami University; Earlham College; Miami University pbaker1@swarthmore.edu
The timing of the transition from embryo to hatchling is an important trait in the life history of turtles. For aquatic species, this ontogenetic shift effectively occurs when the precocial neonates tunnel out of their subterranean nest chamber and migrate to water. In theory, hatchlings that emerge synchronously, within and among nests, gain a survival advantage over hatchlings that emerge independently. We examined emergence patterns for seven species of freshwater turtles that share a nesting area in northern Indiana. Four species (Apalone spinifera, Chelydra serpentina, Emydoidea blandingii, and Sternotherus odoratus) emerge from the nest in late summer or early fall of the same year. However, hatchlings of three species (Chrysemys picta, Graptemys geographica, and Trachemys scripta) usually overwinter in the nest and, despite potential for intermittent frost exposure during hibernation, emerge the following spring. Counter to our expectation, interspecific and intraspecific emergence from the nest was more synchronous in the fall than in the spring. Average date of fall emergence from the nest did not vary among species; however, we observed a species-specific pattern of emergence in spring. Chrysemys picta emerged in late March and early April and, on average, these hatchlings left their nests two weeks earlier than G. geographica and four weeks earlier than T. scripta. Although winter severity varied among years, no relationship between minimum nest temperature and either the average date of emergence or emergence duration was found. By emerging earlier, hatchling C. picta can gain a survival and/or growth advantage over other spring-emerging species. The fitness benefits of early emergence may lead to the improvement of cold-hardiness adaptations in northern populations.
