Metabolism, temperature relations, maternal behavior, and reproductive energetics in the ball python (Python regius)

Abstract

Thermogenic incubation has been documented in two large species of pythons, but the phenomenon has not been studied in small species with concomitantly large heat transfer coefficients. We describe behavior, metabolic rates, mass changes, and temperature relations for adult ball pythons (Python regius), the smallest member of the genus, during the reproductive cycle. Egg and hatchling metabolism and hatchling growth rates were also examined. Rates of oxygen consumption ( $$\dot V_{O_2 } $$ ) of both gravid and non-gravid snakes showed typical ectothermic responses to changing ambient temperature (T a). TheQ 10 forT a's of 20–35°C was 2.2–2.3. The $$\dot V_{O_2 } $$ of gravid females was significantly greater than that of non-gravid snakes at allT a. Maximum oxygen consumption ( $$\dot V_{O_2 } $$ max) during forced exercise was about 12 times resting $$\dot V_{O_2 } $$ atT a=30°C. Eggs (5–6 per female) were laid in April. Total clutch mass was approximately 32% of the females' pre-oviposition mass. After oviposition, mother snakes coiled tightly around their clutches and remained in close attendance until the eggs hatched in June. Sudden decreases inT a elicited abrupt but transient 2- to 4-fold increases in the $$\dot V_{O_2 } $$ of incubating females. Similar responses were not observed in non-incubating snakes. The steady-state $$\dot V_{O_2 } $$ of incubating females was independent ofT a. In no case was body temperature (T b) elevated more than a few tenths of a degree aboveT a in steady-state conditions. The $$\dot V_{O_2 } $$ of developing eggs increased sigmoidally through the 58–70 day incubation period. Total oxygen consumption during incubation atT a=29.2°C was about 3.61 per egg. Young snakes quadrupled their mass during their first year of growth. Compared to larger python species which are endothermic during incubation, ball pythons have similar aerobic scopes and higher mass-specific $$\dot V_{O_2 } $$ max. However, effective endothermy in ball pythons is precluded by high thermal conductance and limited energy stores.