Increased nest temperature during winter does not affect residual yolk metabolism of hatchling painted turtles (Chrysemys picta).

Abstract

Rising global temperatures have a wide range of effects at organismal, population, and ecosystem levels. Increased winter temperatures are expected to alter the energetics of species that are dormant during this time. Hatchling painted turtles (Chrysemys picta) spend their first ∼8 months in shallow nests on land, where they putatively rely on residual yolk reserves to fuel energetic demands during this period of inactivity before they emerge in the spring. We performed a laboratory experiment to characterize changes in residual yolk quantity in hatchling C. picta and experimentally tested the effect of temperature on residual yolk, hatchling size, and survival over the winter brumation period. We manipulated winter nest temperature by simulating two natural thermal regimes ("low" vs "high" treatments) and one regime that approximates warmer temperatures expected by 2100 ("future" treatment). Because high temperature increases metabolism, we predicted that the future temperature treatment would decrease the amount of residual yolk remaining by the end of winter and reduce hatchling mass and survival. Residual yolk over winter did not differ from that before winter, and the temperature had no effect on the quantity of residual yolk or hatchling survival by the following spring. However, hatchlings that experienced future temperatures lost more mass over winter than those from the other treatments. These results correspond with previous work indicating that residual yolk does not fuel the energetic needs of hatchlings during winter. The effect of future warming temperatures on body mass may have negative consequences during energetically demanding activities during spring emergence and dispersal.