Reduced heat production in the bushy-tailed gerbil Sekeetamys calurus (Rodentia) as an adaptation to arid environments

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Abstract
Heat production (measured as oxygen consumption-VO2) and overall thermal conductance (C) were studied in two populations of the bushy-tailed gerbil Skeetamys calurus from two extremely different habitats, the Dead Sea shores (DS) and the high mountains of Southern Sinai (HMS). S. calurus from both populations, when acclimated to ambient temperature (Ta) of 28.degree.C with a photoperiod of 12L:12D showed minimal VO2 of 0.78 ml O2/g .cntdot. h in a thermoneutral zone of Ta = 34-36.degree.C. This value is 44% lower than the predicted (Klieber 1961). Body temperature in this zone is 37.7.degree.C for DS mice and 37.5.degree.C for HMS mice. A significant difference between mice from the two populations was observed in VO2 measured at Ta = 6.degree.C, VO2 in HMS mice was 15.5% higher than in DS mice. Overall thermal conductance for DS mice is 0.17 .+-. 0.02 ml O2/g .cntdot. h.degree.C and for HMS mice 0.18 .+-. 0.02 ml O2/g .cntdot. h.degree.C. These values are 30% and 34% higher than the expected values (Bradley and Deavers 1980) for rodents with a body mass of 59.5 g and 56.9 g respectively, but equals the values found in the golden spiny mouse Acomys russatus from the same habitats; although the pelts are markedly different. The low basic heat demands on one hand and the high thermal conductance on the other hand support the idea that this species originated in hot acid region, and penetrated to colder habitats by increasing heat production capacity, rather than decreasing their thermal conductance.