Seasonal anorexia in the male red-sided garter snake, Thamnophis sirtalis parietalis

Many animals show seasonal shifts in behaviors that coincide with breeding, migration, or hibernation. These behavioral shifts provide ideal opportunities to study the regulation of behavior. The red-sided garter snake (Thamnophis sirtalis parietalis) spends 8 months of the year inactive in underground hibernacula, 1 month breeding, and 3 months feeding to build up enough energy stores to survive the following winter. Although they emerge from 8 months of hibernation with severely depleted energy reserves, they do not feed until weeks later, after the breeding season. We tested the hypothesis that this lack of feeding during the breeding season is due to a shift in behavior rather than the distribution of food and potential mates. Male garter snakes were given a series of choices between pursuing a breeding or feeding opportunity. The proportion of tests in which males selected feeding over breeding gradually increased throughout the study period, reaching almost 100% in the final tests. Males also were given opportunities to feed and court at the beginning and end of the study. Males initially refused food and courted females, but when retested at the end of the study they fed and did not court females. Thus aphagia during the breeding season is due at least in part to an endogenous shift in behavior.