Summary 1.Reproductive costs can affect survival and future reproduction. In winter and in short photoperiods, some individuals within populations of temperate-zone rodents inhibit reproduction and decrease food intake, while others do not. 2. Two lines derived from a natural population of White-Footed Mice and selected to maintain or inhibit reproduction in short photoperiod were tested for two potentially correlated responses to selection: changes in food intake and body mass. Mice were raised to age 70 days in short or long photoperiod, following which testis size, body mass and food intake were measured over a 2-week period. 3. In both lines and both photoperiods, there was an apparent response to selection in testis size and a correlated response to selection in food intake but not body mass. In both photoperiods, mice in the line selected for winter reproduction ate 50% more than mice in the line selected for winter reproductive inhibition. Mice in an unselected control line were intermediate for testis size and food intake. 4. The increased food intake in a line of mice with a genetic tendency for winter reproduction suggests a potential cost of winter reproduction and a potential microevolutionary trade-off related to this cost of reproduction.