Cohort variation in offspring growth and survival: prenatal and postnatal factors in a late-maturing viviparous snake.

1. Recruitment to adulthood plays an important role in the population dynamics of late-maturing organisms as it is usually variable. Compared to birds and mammals, few studies assessing the contributions to this variation of environmental factors, offspring traits and maternal traits have been carried out for late-maturing snakes. 2. Cohort variation in recruitment through offspring growth and survival in the meadow viper (Vipera ursinii ursinii) was evaluated from 13 years of mark-recapture data collected at Mont Ventoux, France. In this species, females are mature at the age of 4-6 years and adult survival and fecundity rates are high and constant over time. 3. Offspring were difficult to catch during the first 3 years of their lives, but their mean annual probability of survival was reasonably high (0.48 +/- 0.11 SE). Mass and body condition at birth (mass residuals) varied significantly between years, decreased with litter size, and increased with maternal length. 4. Cohorts of offspring in better condition at birth grew faster, but offspring growth was not affected by sex, habitat or maternal traits. 5. Survival varied considerably between birth cohorts, some cohorts having a high-survival rate and others having essentially no survivors. No difference in mass or body condition at birth was found between cohorts with 'no survival' and 'good survival'. However, offspring survival in cohorts with good survival was positively correlated with mass at birth and negatively correlated with body condition at birth. 6. Thus, variation in offspring performance was influenced by direct environmental effects on survival and indirect environmental effects on growth, mediated by body condition at birth. Effects of maternal traits were entirely channelled through offspring traits.