Reproductive Tactics and Female Body Size in Butler's Garter Snake, Thamnophis butleri

Abstract

Reproductive strategies of snakes are complicated by the fact that these animals have indeterminate growth. Larger females can produce more offspring, but whether female size affects the size of individual offspring has not been carefully examined. In the viviparous garter snake, Thamnophis butleri, measures of neonate size (snout-vent length, mass or mass/SVL) were posi- tively correlated with measures of female size (length, mass, or mass/SVL) and negatively correlated to clutch size. Relative clutch mass (RCM: total clutch mass/female mass, an operational measure of reproductive effort) did not change with increase in female size. However, RCM per progeny decreased with female size, which would allow larger females to produce clutches of larger numbers with less effect on neonate size.