Intensive parental care improves reproductive success. Why, then, do most animal species not provide parental care to their progeny? Life history theory suggests that the costs must be too high unless they are balanced by considerable fitness benefits. The notion that intensive parental care necessarily entails major costs is based both on intuition and on abundant empirical data. We monitored intensive parental care during brooding in 48 female ball pythons in equatorial Africa (south Togo). Female ball pythons remain coiled around their clutch for 2 months and refuse to feed during nest attendance. Surprisingly, brooding females lost less than 6% of their initial body mass over this 2-month period. The magnitude of mass loss was independent of the duration of brooding (experimentally manipulated to 0, 15 or 60 days) or clutch size (normal, enlarged and reduced clutch sizes). Maternal brooding substantially improved hatching success at little energy cost to the female. This paradoxical result reflects the high ambient temperatures in the study area, meaning that only rarely did nest-attending females need to shiver (a costly thermogenic behaviour observed in all python species). The presence of the mother tightly coiled on the clutch reduced water loss and avoided deleterious yolk desiccation. Thus, intensive brooding over a long period does not necessarily entail major energy expenditure for the mother, but none the less can significantly improve reproductive success. Maternal energy costs during brooding (direct expenditure and possible foregone foraging opportunities) were not influenced by clutch size, demonstrating fecundity-independent costs of reproduction.