THE RESPIRATORY ENVIRONMENT OF THE NAMIB DESERT GOLDEN MOLE

We measured the partial pressure of oxygen (Po-2) in the interstitial gas surrounding the sand-swimming Namib mole Eremitalpa granti namiben sis. At a sand temperature of 26 degrees C, which produced a nearly ma ximal rate of oxygen consumption, the Po-2 near the noses of the anima ls averaged only 0.9 kPa (6.7 Torr) below the level in the free atmosp here. High oxygen availability was a result of the notably low metabol ic rate in the 20 g mammals and the dry, porous and metabolically inac tive nature of dune sand. A mathematical model indicated that normal m ammals weighing 200 g or more could comfortably exist completely encas ed in dune sand. We concluded that the moles' small size and low metab olic rate are not adaptations to hypoxia or hypercapnia underground bu t are probably related to low food availability and the energetic cost of foraging in their desert environment. (C) 1996 Academic Press Limi ted