The Xenarthra consists of anteaters, armadillos, and sloths.  They are second only to the Monotremata in having low basal metabolic rates (Lovegrove 1996).  Lovegrove (2000) suggest two reasons large non-carnivorous mammals would require a high metabolic rate, both connected to mobility.  One is to escape predators and the other is to be able to move large distances to seek out sufficient food.  Many Xenarthra are covered in spines or armor, which removes the necessity of speed to escape predators.   Xenarthra also have the longest history of using specialized diets among mammalian lineages (Eisenberg 1981).  If sufficient food would always be available in a small area, only a slow rate of metabolism would be required for any required movements.

                Morrison (1945) reported that a pregnant-3-toed sloth, a baso-endotherm, lost body temperature when exposed to the cold only about a third as fast as previously observed in non-pregnant sloths.