Heterothermy in elephant shrews, Elephantulus spp. (Macroscelidea): daily torpor or hibernation?

The physiological parameters of heterothermy (e.g. minimum body temperature and oxygen consumption, percentage metabolic reduction, and bout length) w ere measured in two species of Elephantulus elephant shrews (Elephantulus m yurus and Elephantulus rozeti; Macroscelidea) as a function of ambient temp erature. Both species displayed deep torpor whereby the body temperatures o f ca. 5 degreesC and oxygen consumption as low as 2% of basal metabolic rat e were attained. Torpor bout length (n = 57 bouts) never exceeded 24 h. The se data are characteristic of both hibernation (minimum body temperature an d metabolism) and daily torpor (bout length), and argue that these two phys iological responses may not necessarily have separate evolutionary origins.