The metabolic cost of reproduction in an oviparous lizard

1. Studies of reproductive effort in ectotherms have focused primarily on the energetic investment in gamete production; much less is known about the indirect energetic costs of reproduction, such as increased metabolic costs of maintenance or activity. 2. The metabolic cost of reproduction in the oviparous lizard, Sceloporus undulatus, was investigated by measuring the metabolic rate of females prior to and following oviposition. 3. The metabolic rates of gravid females were adjusted for embryonic metabolism by subtracting the metabolic rate of egg clutches, measured immediately after oviposition. 4. The metabolic rate of females when gravid was elevated by 122% compared with that when non-gravid. The difference was not detected until the metabolic rates of gravid females were adjusted for the metabolic rates of the embryos. 5. The increment in metabolic rate associated with reproduction was not correlated with clutch mass or body mass, indicating that different components of reproductive effort (i.e. metabolism vs gametic investment) may not covary in a predictable fashion. 6. Indirect energetic costs of reproduction constitute a substantial portion of the reproductive effort of female S. undulatus, and should be incorporated into theoretical considerations of life history.