Maternal carryover drives post-weaning survival of juveniles in a long-lived mammal

Abstract

The decisions and conditions of animals often carry over to influence fitness in subsequent seasons or years. The condition, choices, and behaviors of parents may have a huge influence on offspring survival, not only when they are nutritionally dependent (i.e., pre-weaning or pre-fledgling), but also after they have reached independence but before adulthood (i.e., post-weaning or post-fledgling). Using a long-lived, iteroparous mammal, we evaluated the hypothesis that carryover effects of a mother’s condition (i.e., age and nutritional condition) and her behavior and decisions during the first few months of her offspring’s life will influence survival of juvenile deer after they reach nutritional independence—during their first migration and their first winter. Age of a mother and mass of her neonates at birth influenced if her offspring survived their first winter; mothers who were young or had high body fat produced offspring that were more likely to survive winter. Moreover, mothers could improve overwinter survival of their offspring by delaying the initiation of their autumn migration. Internal characteristics (i.e., body fat and age) and decisions of parents during their offspring’s first year of life carried over to influence survival of those juveniles after they become nutritionally independent. Juvenile animals still carry the costs and face the consequences of their mother’s decisions well into the period of their independence. The influence of parental characteristics on offspring survival once independent demonstrates the importance of considering how environmental and behavioral characteristics influence survival across generations.

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