Metabolism and evaporative heat loss in the dik-dik antelope ( Rhynchotragus kirki)

Abstract

1. 1. Under controlled conditions, the rate of oxygen consumption ( V ̇ O 2 ) respiratory frequency, evaporative water loss, heat balance, rectal ( T rec ) and surface temperatures were determined in the dik-dik antelopes at ambient temperatures ( T a ) ranging from 1 to 44°C. 2. 2. The thermal neutral zone was found to be between 24 and 35°C. 3. 3. Respiratory frequency ranged between 27 and 630 breaths/min. 4. 4. At a T a of 44°C, 95% of the heat produced by the dik-dik was lost via respiratory evaporation. Despite an increase in T rec , cutaneous evaporation did not increase. 5. 5. During panting, V ̇ O 2 increased in accordance with the expected Q 10 effect, contrary to earlier findings. 6. 6. Measurements of circadian rhythm [LD 12:12 (7–19) CT26°C] in V ̇ O 2 showed that the minimum .VO 2 (0.42ml O 2/g/hr) occurred at midnight while the maximum (0.78ml O 2/g/hr) occurred at midday. The 24 hr mean V ̇ O 2 was 0.61 ml O 2/g/hr. 7. 7. These measurements suggest that in nature, determinants other than light may be responsible for triggering the variations observed in V ̇ O 2 .