Polyunsaturated lipid diet lengthens torpor and reduces body temperature in a hibernator.

Membrane lipids of vertebrate animals that tolerate cold are high in polyunsaturated fatty acids. Because the lipid composition of cellular membranes in mammals can be experimentally altered by diet, we investigated whether a diet rich in polyunsaturated fatty acids would lengthen bouts of torpor and reduce the minimum body temperature in hibernating chipmunks (Eutamias amoenus) compared with a diet rich in saturated fatty acids. Animals on the highly unsaturated diet showed significantly longer bouts of torpor, lower minimum body temperatures, and lower metabolic rates than those on a saturated diet. Animals on a control diet were intermediate. These dietary adjustments apparently influence the control of body temperature by the central nervous system, which results in a modification of the pattern of torpor. The observations also suggest a role of nutritional ecology in hibernation.