INDIVIDUAL VARIATION IN METABOLISM AND REPRODUCTION OF MUS - ARE ENERGETICS AND LIFE-HISTORY LINKED

The possibility of functional relationships between energetics and life-history characteristics has been of considerable interest to evolutionary ecologists. Among species of mammals, life-history variables generally are not correlated with mass-independent basal metabolic rate, with the possible exceptions of maximal intrinsic rate of increase, litter size and reproductive effort during lactation. Whether this is generally true at the level of variation among individuals within a population (individual variation) is unclear. Therefore, we tested whether basal or maximal metabolic rates of random-bred female mice (Mus domesticus) were correlated with the size of their litters, litter mass, or mean offspring mass. The effects of variation in maternal mass, maternal age, experimental block and duration of fasting (for basal metabolic rate) were removed by calculating residuals from multiple regression equations. Basal and maximal metabolic rate were not significantly correlated with any of the life-history variables we studied. Thus, our results are generally consistent with those from interspecific comparisons of mammals: little evidence suggests necessary associations between metabolic rates and life history.