Postnatal Variation in Metabolism and Body Temperature in a Precocial Lagomorph

1. This paper explores the relationship between energy expenditure, body size and the capacity for homeothermy in young of a precocial mammal. 2. Metabolism and rectal temperature (T b ) were measured during postnatal development in 4-81-day-old white-tailed jackrabbits (Lepus townsendii). 3. Whole-animal metabolism increased with age, mass-specific metabolism decreased with age, and mass-independent metabolism showed no age-related change. 4. Jackrabbits 4-5 days old responded to low ambient temperature (T a ) by increasing metabolism, but nonetheless, their T bS declined at low T a