| Summary: | Age-related changes in maternal reproductive allocation for long-lived species are a key prediction from life-history theory. Theoretical and empirical work suggests that 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. Here, we use a hierarchical modelling approach to investigate the 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. We find that maternal allocation increases with age for young mothers during both the pre-natal and post-natal periods. In contrast, older mothers demonstrate a senescent decline in pre-natal allocation but allocate more of their declining resources to their offspring during the post-natal 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. Our results indicate that maternal allocation changes over a mother's reproductive life span and that age-specific differences differ in notable ways in pre-natal and post-natal periods. Data for maternal masses near parturition.This file contains the data used for models of maternal mass near parturition and contains the following columns: Mass (kg), momAGE.c (maternal ages in years at weighing, centered using the mean), momAGE.c.sq (the square of the previous term), momAGE.log (the log transform of maternal age in years, made by subtracting the minimum age from each animal and adding a small constant), PrevState (breeding state the previous season), NPrevPup.c (the number of previous pups for each mother, scaled by the average number of pups at each age), Season (year of measurement).mommasses_publication.csvData ...
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