Bioenergetics of an Herbivorous Rodent Otomys irroratus

The vlei rat Otomys irroratus, a diurnally active rodent, lives primarily in grassland habitats aboveground, close to water sources, on a vegetarian diet of grass leaves, stems, and herbs. Heat production and dissipation and energy intake were studied in vlei rats (mean body mass, $M_{b} = 102 g$). Low metabolic rates (0.832 ± 0.18 ml O₂/g • h) in the thermoneutral zone (24-28 C), low energy intake (141.08 kJ/24 h • 100 g $M_{b}$), and low overall minimal thermal conductance (0.080 ± 0.01 ml O₂/g • h• 1 C; measured at an ambient temperature of 22 C) are characteristic features of this species. Nonshivering thermogenesis was measured as the response to a noradrenaline injection. After the administration of 1.2 mg/kg to an anesthetized individual, an increase of 3.1 times in VO₂ was recorded. This increase was not accompanied by an increase in body temperature. The results of this study reflect the bioenergetic and thermoregulatory adaptations of the vlei rat to its habitat and habits.