BOWDEN, R.M.*; JANZEN, F.J.; Illinois State Univ.; Iowa State Univ.: Growth and Reproduction During a Transitional Life History Stage

Ontogenetic changes in reproductive characters can impact organismal life history. A variety of factors including reproductive frequency, clutch size, and egg size have been shown to increase with female age or body size in turtles. Previous research has also found age-related and seasonal variation in steroid hormone content in yolk. We performed a multiyear study to investigate longitudinal changes in reproductive parameters in a marked population of the painted turtle, Chrysemys picta. Females were classified at the outset of the study as having either high nesting experience (HNE) with at least 6 years prior experience, or low nesting experience (LNE) with 0-2 years prior experience. Nesting was monitored from 2002-2005 and we recorded a number of parameters including linear measures of female body size, clutch size, egg size, nest overstory cover, and nest location relative to shore. Eggs were also collected to determine testosterone and estradiol concentrations in yolk. Preliminary analyses indicate that LNE females grew faster and produced fewer clutches than HNE females during the course of the study. Restricting the analysis to females that nested multiply (2-3 clutches/year) in more than one year of the study, we found that LNE females still had a significantly higher growth rate than HNE females, suggesting that some LNE females are capable of both rapid growth and high reproductive frequency. Hormone analyses indicate that eggs from LNE females contain higher levels of testosterone than those from HNE females, while estradiol levels vary between first and second clutches. These data suggest that LNE females are experiencing a transitional period of maturation during which they must balance allocation to individual growth and to reproductive effort.