Maternal life history of white-tailed deer: factors affecting fetal sex allocation, conception timing, and senescence

Abstract

Questions: How does maternal condition and regional variation in resource abundance affect fetal sex ratio allocation, timing of litter conception, and decreased fecundity due to senescence? Data studied: We used female white-tailed deer (Odocoileus virginianus) maternal age and mass and reproductive tract data (number and sex of fetuses) collected from 1995 to 2011 throughout Alabama. Methods: Fetal sex ratio allocation: We aged collected fetuses to determine conception date and examined the effects of maternal age and mass, litter size, and conception timing (relative to site-specific average conception timing). Timing of litter conception: We examined effects of maternal characteristics. Fecundity: We examined effects of maternal age and mass. In all models, we assessed the effect of regional variation in resource abundance. Conclusions: Fetal sex ratio allocation: The only significant predictor was conception timing, and sons were more likely as conception date was closer to the peak of breeding. We did not find support for Trivers-Willard or the local resource competition hypothesis. Timing of litter conception: Maternal age, mass, and their interaction (maternal age × mass) explained conception timing, with smaller females conceiving further from the mean conception date among younger females and larger females conceiving further from the mean conception date among older females (likely related to reproductive output in the prior breeding season). Fecundity: Not previously demonstrated, we found support for age-related reproductive senescence in female white-tailed deer.