The Timing of Reproduction in the Lizard Lacerata vivipara: Differences between Individual Females

Abstract

During a field study examining the live-bearing lizard Lacerta vivipara, we estimated the timing of mating, ovulation and parturition in individual females. Reproduction was synchro- nized, especially among the larger (older) females. The timing of all reproductive acts was inversely correlated with female size: smaller females have delayed reproductive activities relative to the larger lizards. The timing of copulation and parturition were related to the timing of ovulation in individual females. Thus, females which finished vitellogenesis early tended to mate early and gave birth to their young on an early date. Benefits of early reproduction include: attainment of the highest size-adjusted body weight by the post-reproductive females at the onset of hibernation; early born juveniles reach the largest size at the end of the activity season. The delay of reproduction in the smaller females is coincident with their relatively high growth rates and reduced lipid stores. Allocation of energy to reproduction appears to occur at a slow rate in the smaller adults and probably accounts for the delay in reproductive activities. We therefore consider the postponement of reproduction as a cost of rapid growth. The timing of reproduction in an individual female seems to be the result of an interaction between the benefits of early breeding and the pay-offs of rapid growth.