SREL Reprint #2084




A Neglected Life-History Trait: Clutch-Size Variance in Snakes


School of Biological Sciences A08, The University of Sydney, NSW 2006, Australia



Department of Biological Sciences, Southeastern Louisiana University, PO Box 814, Hammond, LA 70402, USA and Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802, USA


Most analyses of life-history traits have focused on mean values rather than their associated variances. We review published and original data on snakes. including records gathered over manv years on single populations, to examine patterns in clutch-size variability in these animals. Within single populations, the coefficient of variation of clutch size did not vary significantly with maternal body size, or among years. The stability of clutch-size variance through time is consistent with experimental studies showing no significant influence of food intake rates on this characteristic. Clutch-size variances did not differ between viviparous and oviparous snakes, but were dependent upon allometric relationships involving maternal body size and the relationship between clutch size and body size. Clutch-size variability was highest in species with relatively variable female sizes, and with a high rate of increase in clutch size with increasing body size. These two factors acted to magnify the extent of clutch-size variability engendered by variability in maternal body sizes. The relationships among these variables were similar in the two squamate Suborders, but the larger body sizes and mean clutch sizes of snakes resulted in clutch-size variances being higher in snakes than in lizards.

SREL Reprint #2084

Shine, R. and R.A. Seigel. 1996. A neglected life-history trait: clutch size variance in snakes. Journal of Zoology 239:209-223.


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