Energetics of gestation relative to lactation in a precocial rodent, the guinea pig (Cavia porcellus)

Caviomorph rodents stand out by showing long gestation periods and by produ cing few, extremely precocial young. This study compares the energy cost of gestation vs lactation in the guinea pig Cavia porcellus. It tests whether the long gestation period (68 days) relative to the total period of matern al care (88 days) of this species results in a high overall energetic effic iency of reproduction. Although maternal net production during gestation wa s as high as during lactation, the net energy cost of gestation was much lo wer than the energy cost of lactation. Mothers' average increase in energy intake (above the nonreproductive level) was only 16% during gestation, but 92% during lactation. Similarly, the peak in maternal energy intake was lo w during gestation (2.4 times basal metabolic rate) compared to the peak du ring lactation (3.7 times basal metabolic rate). Consequently, the efficien cy of energy conversion into offspring tissue during gestation (62%) was al most twice as high as the efficiency during lactation (35%). The results ag ree with the hypothesis that a prolonged gestation period increases the ove rall energetic efficiency of reproduction.