Reproduction in a Typical Capital Breeder: Costs, Currencies, and Complications in the Aspic Viper

Female aspic vipers (Vipera aspis) are ‘‘capital breeders,’’ and delay reproduction until they have amassed large energy reserves. Data from an eight-year mark– recapture study on free-ranging vipers suggest that potential costs of reproduction were high for these animals, in terms of survival as well as growth and energy storage. Females that reproduced experienced higher mortality rates than nonreproductive females and, hence, exhibited a tendency toward semelparity, grew less, and devoted most of their energy stores to reproduction. Both the depletion of body reserves and the low survival of reproductive females translated into significant costs (decrements of lifetime reproductive success [LRS]). However, the cessation of growth during pregnancy had no detectable effect on LRS. Most females produced only a single litter during their lifetimes. A female’s ‘‘costs’’ in energy terms were not negatively correlated with her future reproductive output, probably because female vipers vary considerably in the rate at which they can accumulate energy. This notion is supported by the observations that (1) females with higher initial body reserves expended more energy during reproduction, and (2) females that accumulated energy more rapidly after parturition were more likely to survive and to breed again. This kind of variation among females masks any underlying trade-off between current reproductive effort and probable future reproductive success. Despite this complication, a strong link between rates of survival and postreproductive mass recovery suggests that changes in body reserves govern reproductive effort in this species.