Sex and seasonal differences in metabolism in the red-sided garter snake, Thamnophis sirtalis parietalis

Field and laboratory studies revealed that male and female Canadian red-sided garter snakes, Thamnophis sirtalis parietalis, differ in the pattern of body mass gain, nutrient storage, and nutrient availability following emergence from hibernation. In nature males fail to gain weight or store fat until 3 weeks after emergence from prolonged (7 months) winter hibernation. In the laboratory males also do not exhibit an increase in body mass following emergence from artificial hibernation (17 weeks) until mating behavior has ended, about 3 weeks after emergence; as in free-living males, fat stores do not increase until all mating behavior has ceased. In contrast, females in both field and laboratory populations gain weight steadily following emergence but exhibit a gradual decrease in the proportion of abdominal fat reserves to body mass. While females exhibit increased serum levels of protein, unchanged levels of glucose, and decreased levels of lipid, males exhibit unchanged levels of protein, increased levels of glucose, and decreased levels of lipid. Males display a greater resting oxygen consumption postemergence compared with females. Oxygen consumption was decreased in both sexes during the period coinciding with mating; at the end of breeding, oxygen consumption increased. These data are consistent with the marked differences in reproductive behaviors between the sexes following emergence from hibernation.