We measured rates of metabolism for a pair of crab-eating foxes, Cerdocyon thous, over a range of environmental temperatures. Basal metabolic rates for Cerdocyon are exceedingly low, averaging 65%-75% of that expected from their body mass. In contrast, thermal conductances were very high, about 140% of that expected from their body mass. These low basal rates of metabolism, in comparison with those measured for other canids, are attributed to the omnivorous food habits of this species. These results suggest that the basal metabolic rate of canids is ecologically labile and sensitive evolutionarily to environmental influences such as food habits and climate. Oxygen consumption for both foxes huddling together was 5%-18% lower than that for both foxes when separated but in the same respirometry chamber. The effects of huddling could thus have a significant effect on the daily energy expenditures of this and, perhaps, other species of canids.