Short- and long-term effects of litter size manipulation in a small wild-derived rodent

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’ energ...