1. Age-related changes in maternal reproductive allocation for long-lived species are a key prediction from life-history theory.
2. Theoretical and empirical work suggests allocation may increase with age due to constraint (increases with experience) or restraint (increases with age in the face of declining residual reproductive value), and may decrease among the oldest aged animals due to senescence in reproductive function.
3. Here we use a hierarchical modeling approach to investigate age-related patterns of change in maternal reproductive effort in the Weddell seal, a long-lived marine mammal with a protracted period of maternal care during which mothers allocate a large proportion of body mass while feeding little.
4. We find maternal allocation increases with age for young mothers during both the prenatal and postnatal periods. In contrast, older mothers demonstrate a senescent decline in prenatal allocation but allocate more of their declining resources to their offspring during the postnatal period. We also find strong evidence for the importance of individual effects in reproductive allocation among mothers: some mothers consistently produce heavier (or lighter) pups than expected.
5. Our results indicate that maternal allocation changes over a mother’s reproductive lifespan and that age-specific differences differ in notable ways in prenatal and postnatal periods.
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