干旱区生态环境知识资源中心

To understand better how complex interactions between environmental variables affect the energy balance of small diurnal animals, we studied the effects of the absence and presence of 950 W m(-2) simulated solar radiation combined with wind speeds ranging from 0.25 to 1.00 m s(-1) on the metabolic rate and body temperature of the round-tailed ground squirrel Spermophilus tereticaudus. As wind speed increased from 0.25 to 1.00 m s(-1), metabolic heat production increased by 0.94 W in the absence of solar radiation and by 0.98 W in the presence of 950 W m(-2) simulated solar radiation. Exposure to simulated solar radiation reduced metabolic heat production by 0.68 W at a wind speed of 0.25 m s(-1), by 0.64 W at 0.50 m s(-1) and by 0.64 W at 1.00 m s(-1). Body temperature was significantly affected by environmental conditions, ranging from 32.5 degrees C at a wind speed of 1.0 m s(-1) and no irradiance to 35.6 degrees C at a wind speed of 0.50 m s(-1) with 950 W m(-2) short-wave irradiance,

In addition, several unusual findings resulted from this study. The coat of S, tereticaudus Is very sparse, and the observed heat transfer of 5.68+/-0.37 W m(-2) degrees C-1 (mean +/- S.E.M., N=11) is much higher than expected from either allometric equations or comparative studies with other rodents of similar mass. Solar heat gain was remarkably low, equalling only 10 % of intercepted radiation and suggesting a remarkably high regional thermal resistance at the tissue level. Animals remained normally active and alert at body temperatures as low as 32.5 degrees C, These findings suggest a unique combination of adaptations that allow S, tereticaudus to exploit a harsh desert environment.