LIFE-HISTORY OF VIPERA-URSINII-URSINII AT MONT-VENTOUX (FRANCE)

The life history of Vipera ursinii ursinii at Mont-Ventoux (France) is documented on the basis of mark-recapture data collected on a long-te rm field study (1973-1991). Traits under consideration relate to the i ndividual growth, survival and reproduction of the snakes. Demographic variations (i.e., among individuals), temporal variations (across yea rs) 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 t he determinants of reproductive effort in this species. Plasticity is demonstrated in individual growth (spatially variable), parturition da te 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 exoge nous factors (local humidity and duration of sunny conditions in summe r, respectively). Litter size (corrected for maternal body size) and n eonate mass vary across years. Controlling for this time effect, litte r 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 i n litter size that would result as a by-product of a physiological tra de-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 probabilit ies (that depend on age), reproductive frequency (dominated by a bienn ial cycle), relative clutch mass (that usually increases with maternal size) and lifter sex ratio seem to be strongly canalized. Reproductiv e effort is assessed by the relative clutch mass, which tightly correl ates with post-partum body condition. Except in one year, relative clu tch mass increases with body size. In fact, this relationship might di ffer among broods that are laid after a non-reproductive year versus t hose laid on the second of 2 consecutive breeding. Reproductive effort per offspring is independent of maternal size and neonate gender, whi le litter sex ratio is biased (in Savor of males). There is no signifi cant 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 sta tus; offspring mass as a possible indicator of juvenile survival is no t influenced by maternal reproductive effort. In contrast a major cost of reproduction impacts on potential fecundity, through the usual alt ernation of reproductive and non-reproductive years, although consecut ive breeding are feasible. Determinants of reproductive frequency may involve the effect of current reproductive effort on subsequent reprod uctive status, and that of body size. Finally, males might undergo a s imilar cost in potential fecundity, as they also, seem to alternate ye ars of high and low sexual activity. In conclusion, we discuss the con straint exerted by the peculiar foraging ecology of the Orsini's viper (whose diet is almost entirely insectivorous) upon the evolution of i ts life history.