DIETARY FATS AND TORPOR PATTERNS IN HIBERNATING GROUND-SQUIRRELS

The effect of a sunflower oil diet (rodent chow with 10% addition by w eight of sunflower seed oil, rich in linoleic acid), a sheep fat diet (rodent chow with 10% addition by weight of sheep fat, rich in saturat ed fatty acids and oleic acid), and a control diet (rodent chow withou t added fat or oil) on the pattern of torpor was investigated in the g round squirrel Spermophilus saturatus, a relatively large (250 g) hibe rnator. Torpid S. saturatus on the sunflower oil diet showed a lower m inimum body temperature (2.1 vs. 3.5-degrees-C), a lower metabolic rat e (0.029 vs. 0.043 mL 02/g . h)), and longer bouts of torpor (252 vs. 193 h at an air temperature of -1.0-degrees-C) than animals on the she ep fat diet. These physiological variables showed intermediate values in controls. It appears, therefore, that the composition of dietary fa tty acids, rather than the fat content of the diet, affected torpor pa tterns. It is likely that the observed physiological differences may b e explained by diet-induced compositional differences in body lipid co mposition.