KARPOVICH, S.*; TOIEN, O.; BARNES, B.M.: Does Active Metabolic Suppression Occur During Entry into Torpor?

Captive S. parryii from Toolik Lake, Alaska were housed at University of Alaska Fairbanks and exposed to ambient temperatures (T_a) of +2, -5 and -12^oC. Body temperature (T_b) was recorded via telemetry and rates of oxygen consumption (VO₂) and carbon dioxide production were measured with open flow respirometry to estimate the energetic costs of ground squirrels during the re-entry phase of arousal episodes. Explanations of the mechanisms that allow hibernators to depress metabolic rate during entry into torpor are controversial. Does metabolic rate drop as a consequence of Q₁₀ effects accompanying decreased T_b or T_brain, OR does T_b decrease as a result of temperature-independent metabolic suppression? Preliminary data indicates that Q₁₀ of T_b vs. VO₂ for trials at each T_a (+2, -5 and -12^oC)average 5, which is above the biologically expected Q₁₀ range of 2-3. This indicates metabolic suppression independent of body temperature. Rates of T_b cooling curves are different for trials run at the 3 T_as, with no change in the rate of VO₂ decrease. This also supports the metabolic suppression theory. T_brain data will be examined.