Luiselli L, Capula M, Shine R
Department of Animal and Human Biology, University of Rome La "Sapienza", via A. Borelli 50, 1-00161, Rome, Italy.
School of Biological Sciences A08, The University of Sydney, 2006, NSW, Australia.
Oecologia. 1996 Apr;106(1):100-110. doi: 10.1007/BF00334412.
A 5-year mark-recapture study of smooth snakes (Coronella austriaca) in the Carnic Alps (1100 m above sea level) of north-eastern Italy provided extensive information on the biology and life-history of these small viviparous snakes. Offspring were relatively large (mean=15 cm total length, 2.9 g) when they were born in late summer, and females grew to maturity (44 cm, 50 g) in approximately 4 years. Larger neonates retained their size advantage for at least 12 months, but did not have a higher probability of survival. Although sexual size dimorphism (at birth and at mean adult body sizes) was minor, the sexes differed significantly 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 males fed primarily on lizards, larger females shifted to feeding less frequently, but taking larger prey (mammals and snakes). Reproductive output increased strongly with maternal body size: larger females reproduced more frequently, produced larger litters of larger neonates, had higher relative clutch masses (RCMs), and had a lower proportion of stillborn off-spring. Most females produced a litter every 2nd or 3rd year. We did not detect significant year-to-year variation in reproductive traits over the 5 years of our study. Females were consistent from one litter to the next in several traits (e.g., litter sizes, offspring 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 averaged 50/50, but sex ratios tended to be more male-biased in litters that were unusually large relative to maternal body size, and in litters containing a high proportion of stillborn offspring. "Costs" of reproduction appear to be high in this population, in terms of both energy allocation and risk. Reproduction reduced growth rates, and females that recovered condition more quickly in the year after reproduction were able to reproduce again after a briefer delay. Mortality was highest 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 energy for reproduction.
在意大利东北部卡尔尼克阿尔卑斯山（海拔1100米）对滑蛇（Coronella austriaca）进行的一项为期5年的标记重捕研究，提供了关于这些小型胎生蛇类生物学和生活史的丰富信息。夏末出生时，幼蛇相对较大（全长平均15厘米，体重2.9克），雌性大约4年可长到成熟（44厘米，50克）。较大的幼蛇至少在12个月内保持其体型优势，但生存概率并不更高。虽然两性异形（出生时和成年平均体型时）较小，但两性在几个方面存在显著差异。幼年时期雌性比雄性生长得更快，成年雌性在饮食习惯上与种群其他个体不同。幼年（两性）和成年雄性主要以蜥蜴为食，而体型较大的雌性进食频率降低，但捕食更大的猎物（哺乳动物和蛇）。繁殖产出随母体体型显著增加：体型较大的雌性繁殖更频繁，产仔数更多、幼蛇更大，相对窝卵质量（RCM）更高，死产幼崽比例更低。大多数雌性每2年或3年产一窝。在我们研究的5年中，未检测到繁殖特征的显著年际变化。雌性在几个性状（如窝仔数、幼蛇大小和形状、死产幼蛇比例、RCM）上窝与窝之间保持一致，但这种一致性是由于雌性之间体型差异而非与体型无关的母体效应。总体窝仔性别比平均为50/50，但相对于母体体型异常大的窝以及死产幼崽比例高的窝，性别比往往更偏向雄性。就能量分配和风险而言，该种群的繁殖“成本”似乎很高。繁殖降低了生长速度，繁殖后一年内恢复状况更快的雌性能够在更短的延迟后再次繁殖。繁殖期RCM高的雌性以及产后非常消瘦的雌性死亡率最高。滑蛇繁殖产出随母体体型增加而显著增加，这可能反映出随着雌性体型增大“成本”降低，而饮食转向更大的猎物可能提高雌性积累繁殖能量的速度。
