Measuring Annual Variation in Reproductive Output Reveals a Key Role of Maternal Body Condition in Determining the Size of Eggs in Snakes

Abstract

Long-term studies are especially suited for disentangling the effects of extrinsic and intrinsic factors on both total reproductive investment and reproductive allocation in offspring number versus offspring size. Female reproductive traits of the red-banded wolf snake (Lycodon rufozonatus) from Zhejiang, East China were studied in four years between 1999 and 2014. Egg-laying dates overall extended from late June to late July, and varied among years. Postpartum body mass, clutch size, clutch mass, and egg size were positively related to female size (snout vent length, SVL) in each year. Postpartum body mass, clutch mass, and egg size differed among years after accounting for female SVL, whereas clutch size did not. Setting female SVL at the same level, postpartum body mass was greater in 2010 than in 2014, clutch mass was greater in 2010 than in 2011 and 2014, and egg size was greater in 2010 than in the other three years. Females did not trade off egg size against number. Egg size was positively related to postpartum body condition in each year. Females laid larger eggs in 2010 than in other three years after removing the influence of maternal body condition. Our study provides evidence for the traditional view that reproductive output is highly linked to maternal body size in snakes, but not following Smith and Fretwell’s (1974) classic prediction that females with different amounts of resources to invest in reproduction should give priority to adjusting the number rather than size of their offspring. Maternal body size and condition both are important sources of variation in egg size, but factors other than these two variables may also affect the size of eggs produced by female L. rufozonatus.

Reproductive Output Reveals the Maternal Effects on Offspring Size-Number Trade-Off in Cultured Asian Yellow Pond Turtle (Mauremys mutica)

“…In other reptiles, such as sand lizards, Lacerta agilis , the offspring size is negatively correlated with the offspring number, which implies a diversity of offspring size-number trade-off effects among taxa [ 39 ]. In fact, we also found no evidence of a trade-off between the clutch size and offspring size, which was similar to the study in the red-banded wolf snakes, Lycodon rufozonatus [ 40 ].…”

Sexual Dimorphism and Female Reproductive Characteristics in the Hainan Water Skink (<i>Tropidophorus hainanus</i>) from Hainan, South China

“…We calculated relative litter mass by dividing litter mass by the postpartum female mass (Shine, 1992). We calculated the coefficient of variation [= 100 × (standard deviation/mean) to estimate within-litter offspring size variability; Guo et al, 2022]. To account for the influence of female size on fecundity (litter size), we calculated relative fecundity by using the residuals derived from the regression of litter size against female SVL (Olsson and Shine, 1997).…”

Sexual Dimorphism, Female Reproductive Characteristics and Embryonic Thermosensitivity in the Tonkin Forest Skink (<italic>Sphenomorphus tonkinensis</italic>) from Hainan, South China

“…Post-laying females were weighed and measured for SVL. We calculated relative clutch mass (RCM) by dividing clutch mass by the post-laying female mass and used the coefficient of variation [CV = 100 × (standard deviation/mean)] to estimate withinclutch egg size variability (Guo et al, 2022).…”