Abstract
The production of offspring typically requires investment of resources derived from both the environment and maternal somatic reserves. As such, the availability of either of these types of resources has the potential to limit the degree to which resources are allocated to reproduction. Theory and empirical studies have argued that mothers modify reproductive performance relative to exogenous resource availability and maternal condition by adjusting size, number or sex of offspring produced. These relationships have classically been defined relative to availability of energy sources; however, in vertebrates, calcium also plays a critical role in offspring production, as a considerable amount of calcium is required to support the development of offspring skeleton(s). We tested whether the availability of calcium influences reproductive output by providing female white-footed mice with a low-calcium or standard diet from reproductive maturity to senescence. We then compared maternal skeletal condition and reproductive output, based on offspring mass, offspring number and litter sex ratio, between dietary treatments. Mothers on the low-calcium diet exhibited diminished skeletal condition at senescence and produced smaller and strongly female-biased litters. We show that skeletal condition and calcium intake can influence sex ratio and reproductive output following general theoretical models of resource partitioning during reproduction.
Highlights
Life history theory predicts that mothers should optimize their reproductive success by partitioning resources in a manner that will afford them greatest fitness [1,2]
Poor body condition and food scarcity experienced by mothers during severe El Nino events is associated with reduced offspring body condition in California sea lions (Zalophus californianus) [4], and maternal body condition is positively correlated with weaning mass under typical conditions in Columbian and Richardson’s ground squirrels (Urocitellus columbianus, U. richardsonii) [5,6]
We considered the effects of maternal age, parity, body mass, and calcium intake on factors associated with reproductive performance
Summary
Life history theory predicts that mothers should optimize their reproductive success by partitioning resources in a manner that will afford them greatest fitness [1,2]. To this end, maternal attributes (e.g. condition, age or parity), and the availability of exogenous resources may interact to influence the degree to which resources are invested into the production of offspring. Poor body condition and food scarcity experienced by mothers during severe El Nino events is associated with reduced offspring body condition in California sea lions (Zalophus californianus) [4], and maternal body condition (residuals of body mass/skeletal size) is positively correlated with weaning mass under typical conditions in Columbian and Richardson’s ground squirrels (Urocitellus columbianus, U. richardsonii) [5,6]. The availability of food is positively correlated with litter size in Prairie voles (Microtus ochrogaster) and Columbian ground squirrels [9,10]
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