Metabolic changes in male snakes, Thamnophis melanogaster, during a breeding period

1. Daily basking periods were lengthened substantially during a breeding period in a natural population of the snake, Thamnophis melanogaster. 2. In the laboratory, oxygen consumption of male T. melanogaster significantly increased during a breeding period, compared to pre- and post-breeding levels in the same males. 3. In both laboratory and field males, serum lipid increased initially and then decreased during the breeding period. 4. Serum protein of laboratory males decreased significantly following the breeding period. 5. Serum glucose did not change significantly in laboratory males, but increased significantly during the breeding period in field males. 6. Changes in oxygen consumption and nutrient distribution may reflect changing energy demands attendant with gonadal recrudescence in this snake.