IIASA RepositoryLife history of Vipera ursinii ursinii at Mont-Ventoux (France)J.P.BaronauthorR.FerriereauthorJ.ClobertauthorH.Saint GironsauthorThe life history of Vipera ursinii ursinii at Mont-Ventoux (France) is documented on the basis of mark-recapture data collected on a long-term field study (1973-1991). Traits under consideration relate to the individual growth, survival and reproduction of the snakes. Demographic variations (i.e., among individuals), temporal variations (across years) and spatial variations (between 2 distinct patches of habitat) in the traits are analyzed, as well as phenotypic correlations. In doing so, we get insights into the phenotypic plasticity of V. ursinii and the determinants of reproductive effort in this species. Plasticity is demonstrated in individual growth (spatially variable), parturition date and litter size (temporal variations), and offspring mass (temporal and demographic variations). Spatial variations in individual growth and temporal fluctuations in parturition date might be driven by exogenous factors (local humidity and duration of sunny conditions in summer, respectively). Litter size (corrected for maternal body size) and neonate mass vary across years. Controlling for this time effect, litter size and neonate mass appear to be negatively correlated. We suggest that neonate mass might be subject to endogenous factors, e.g. female mating success if sperm competition occurs-with yearly fluctuations in litter size that would result as a by-product of a physiological trade-off with neonate mass. Litter size varies less amongst individuals than throughout a female's lifespan, whereas offspring mass vary more among litters than within a given litter. Finally, survival probabilities (that depend on age), reproductive frequency (dominated by a biennial cycle), relative clutch mass (that usually increases with maternal size) and lifter sex ratio seem to be strongly canalized. Reproductive effort is assessed by the relative clutch mass, which tightly correlates with post-partum body condition. Except in one year, relative clutch mass increases with body size. In fact, this relationship might differ among broods that are laid after a non-reproductive year versus those laid on the second of 2 consecutive breeding. Reproductive effort per offspring is independent of maternal size and neonate gender, while litter sex ratio is biased (in Savor of males). There is no significant survival cost of reproduction : there is no reduction in survival probability when maturity is reached neither in males nor in females; the adult female survival rate is independent of the reproductive status; offspring mass as a possible indicator of juvenile survival is not influenced by maternal reproductive effort. In contrast a major cost of reproduction impacts on potential fecundity, through the usual alternation of reproductive and non-reproductive years, although consecutive breeding are feasible. Determinants of reproductive frequency may involve the effect of current reproductive effort on subsequent reproductive status, and that of body size. Finally, males might undergo a similar cost in potential fecundity, as they also, seem to alternate years of high and low sexual activity. In conclusion, we discuss the constraint exerted by the peculiar foraging ecology of the Orsini's viper (whose diet is almost entirely insectivorous) upon the evolution of its life history.1996Article

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