LIGON, D. B.; HUSAK, J. F.; PETERSON, C. C.; Oklahoma State Univ.; Oklahoma State Univ.; The College of New Jersey: Variation in resting metabolic rate across season, class, and year in the eastern collared lizard

The metabolizable energy an animal assimilates must meet a variety of costs. Increasing the metabolic efficiency of processes associated with maintenance can, in theory, allow reallocation of saved energy to processes associated with production and activity. We tested our predictions using the collared lizard (Crotaphytus collaris), a species with a polygynous mating system. We hypothesized that, because more energy could be allocated to territory defense, lower maintenance costs would correlate with larger territories among males. In addition, we predicted that among females, which are not territorial, metabolism would vary with reproductive state, and that higher energy demands would translate into larger home ranges as food requirements increased. Maintenance costs were estimated by calculating mass-corrected resting metabolic rates (RMR, oxygen consumption) of lizards in a population in north-central Oklahoma. As predicted, we found that among territorial males, territory size was negatively correlated with RMR. Non-territorial yearling males, representing the lowest social class, exhibited RMR similar to those of late-season adult males. As predicted, female RMR was positively correlated with home range size. Female RMR were lowest in early May before follicles were detected; measurements during and after reproduction did not differ. These results suggest that energetic costs associated with maintenance may influence social status within but not between age classes in males, and that maintenance costs vary with reproductive season in both sexes.