Various hypotheses suggest that the benefit of viviparity lays in the acquisition of an appropriate range of temperatures during incubation, as this phenomenon has evolved from egg laying in many lineages of lizards and snakes, apparently in response to extreme climates. I examined the effects of reproductive condition on thermoregulation in the Argentina boa constrictor (Boa constrictor occidentalis) to offer an insight into the selective forces acting on the critical phase of its life history. Thermal ecology and activity during the mating season were investigated using radiotelemetry.

A differential thermoregulatory behavior was manifested. Body temperatures of reproductive females were significantly higher than those of both reproductive males and non reproductive females. Regression analysis showed that reproductive females had a lower slope and a higher Y-intercept than reproductive males and non reproductive females, suggesting that the reproductive females are better thermoregulators.