Food availability has direct and delayed effects on structural growth and body reserves in garter snakes

Abstract

Phenotypic plasticity in body growth enables organisms to cope with unpredictable paucities in resource availability. Growth traits influence survival and reproductive success, and thereby, population persistence, and early-life resource availability may govern lifetime patterns in growth, reproductive success, and survival. The influence of early-life environment is decidedly consequential for indeterminately growing ectotherms, which rely on available resources and ambient temperatures to maximize fitness throughout life. Using 17 years of mark–recapture data, we evaluate the effects of resource availability on patterns in growth for populations of western terrestrial garter snakes (Thamnophis elegans), which differ along pace-of-life continuums into fast- and slow-living ecotypes. We use an adaptation of the von Bertalanffy estimator to fit structural growth models and linear predictors for body condition to analyze the consequences of annual and early-life prey availability. Snakes from resource-poor early-life environments are primed to exploit conditions in high-prey environments later in life. Slow pace-of-live animals exhibit a greater capacity for compensatory strategies in structural growth, while body condition was best explained by a complex interaction across males and non-gravid females between prey availability and ecotype. Our findings highlight the importance of accounting for context-dependent early-life environments as well as sex-specific reproductive demands when evaluating population traits.