Iteroparous organisms maximise their overall fitness by optimising their reproductive effort over multiple reproductive events. Hence, changes in reproductive effort are expected to have both short- and long-term consequences on parents and their offspring. In laboratory rodents, manipulation of reproductive efforts during lactation have however revealed little short-term reproductive adjustments, suggesting that female laboratory rodents might express maximal rather than optimal levels of reproductive investments as observed in semelparous organisms. Using a litter size manipulation (LSM) experiment in a small wild-derived rodent (the common vole; Microtus arvalis), we show that females altered their reproductive efforts in response to LSM, with females having higher metabolic rates and showing alternative body mass dynamics when rearing an enlarged rather than reduced litter. Those differences in female reproductive effort were nonetheless insufficient to fully match their pups’ energy demand, pups being lighter at weaning in enlarged litters. Interestingly, female reproductive effort changes had long-term consequences, with females that had previously reared an enlarged litter being lighter at birth of their subsequent litter and producing lower quality pups. We discuss the significance of using wild-derived animals in studies of reproductive effort optimisation.
Reproductive parameters for short- and long term effects of litter size manipulation in the common vole: "Short term data"-sheet includes data collected during litter size manipulation. "Long term data" -sheet includes data collected from subsequent reproductive event without manipulation. RMR is resting metabolic rate of the mother measured at day 15-17 of lactation. "Mass_change_ " indicates body mass change of the mother during given period. Days in variable names indicate days after birth. "Mass_change_weaning_pairing%" indicates body mass change of the mother, in percentage, from the weaning of previous litter until the beginning of the next pairing. Data was collected in the laboratory using wild-derived F2 generation (parents) common voles.
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- Cost of reproduction
- life history theories
- litter size manipulation
- Microtus arvalis