Developmental Plasticity of Postweanling Cotton Rats (Sigmodon hispidus) as an Adaptation to Nutritionally Stochastic Environments

Abstract

Elucidating interrelationships between rate of growth and sexual maturation in unpredictable or stochastic environments could increase our understanding of life-history strategies of small mammals. It has been hypothesized that species living in environments where food availability is unpredictable might become sexually mature at smaller sizes and channel excess energy into reproduction rather than into compensatory growth. We explored this hypothesis in female cotton rats (Sigmodon hispidus) by feeding variable levels of dietary protein during early postweanling development (14–45days of age) and monitoring compensatory growth and fitness after nutritional rehabilitation (45–100days of age). Growth was optimum in females fed diets containing 16% protein, with minimal requirements estimated to be 12%. Females fed diets containing <12% protein exhibited suppressed development, including delayed puberty. However, these nulliparous females demonstrated compensatory growth during the early period of nutritional rehabilitation, regardless of the severity of previous restrictions in protein. No long-lasting fitness consequences from postweanling nutritional restrictions were apparent as we observed no difference in date of conception, body mass of dams at parturition, litter size, or rate of growth of neonates. We offer a possible adaptive explanation for this observed plasticity in growth and development.