Comparative energetics of South American cricetid rodents.

1. The effects of body size, food habits and limits of endothermy on the energetics of seventeen species of South American cricetid rodents were examined. The combination of mixed diets, together with close to the expected basal rates of heat production, allows most cricetids studied to maintain effective endothermy; but those that have low basal metabolic rates and small sizes show a state of torpor. 2. Our observations do not support the hypothesis that the absence of torpor in South American cricetid rodents is due to phylogenetic characteristics. 3. The high ecological diversity, as well as the variety of life modes of these rodents, is explained on an energetic basis.