REPRODUCTIVE OUTPUT, COSTS OF REPRODUCTION, AND ECOLOGY OF THE SMOOTHSNAKE, CORONELLA-AUSTRIACA, IN THE EASTERN ITALIAN ALPS

A 5-year mark-recapture study of smooth snakes (Coronella austriaca) i n the Carnic Alps (1100 m above sea level) of north-eastern Italy prov ided extensive information on the biology and life-history of these sm all viviparous snakes. Offspring were relatively large (mean = 15 cm t otal length, 2.9 g) when they were born in late summer, and females gr ew to maturity (44 cm, 50 g) in approximately 4 years. Larger neonates retained their size advantage for at least 12 months, but did not hav e a higher probability of survival. Although sexual size dimorphism (a t birth and at mean adult body sizes) was minor, the sexes differed si gnificantly in several respects. Females grew faster than males during juvenile life, and adult females diverged in dietary habits from the rest of the population. Whereas juveniles (of both sexes) and adult ma les fed primarily on lizards, larger females shifted to feeding less f requently, but taking larger prey (mammals and snakes). Reproductive o utput increased strongly with maternal body size: larger females repro duced more frequently, produced larger litters of larger neonates, had higher relative clutch masses (RCMs), and had a lower proportion of s tillborn offspring. Most females produced a litter every 2nd or 3rd ye ar. We did not detect significant year-to-year variation in reproducti ve traits over the 5 years of our study. Females were consistent from one litter to the next in several traits (e.g., litter sizes, offsprin g sizes and shapes, proportions of stillborn neonates, RCMs), but this consistency was due to differences in body size among females rather than to size-independent maternal effects. Overall litter sex ratios a veraged 50/50, but sex ratios tended to be more male-biased in litters that were unusually large relative to maternal body size, and in litt ers containing a high proportion of stillborn offspring. ''Costs'' of reproduction appear to be high in this population, in terms of both en ergy allocation and risk. Reproduction reduced growth rates, and femal es that recovered condition more quickly in the year after reproductio n were able to reproduce again after a briefer delay. Mortality was hi ghest in reproducing females with high RCMs, and in females that were very emaciated after parturition. The marked increase in reproductive output with increasing maternal body size in C. austriaca may reflect a reduction in ''costs'' as females grow larger, and the dietary shift to larger prey may enhance the rate that females can accumulate energ y for reproduction.