Hibernating at High Temperatures Increases Variability in Arousal Dynamics

In the winter, and presumably due to low resource availability, many mammals enter into a state of torpor wherein body temperature approaches that of ambient temperature and oxygen consumption rates can be as low as 1/100 th of active rates. The canonical hibernation season is not static. Rather periods of torpor are interrupted by predictable periods of euthermy called interbout arousals which allows for a resetting of homeostatic processes. Here, we exposed golden-mantled ground squirrels to a range of ambient temperatures including high temperatures (4, 12, 20, 25, and 30°C). Preliminary analyses demonstrated higher temperatures resulted in decreased maximum rates of rewarming. On average, at 4°C ambient temperature rewarming was 0.14 °C per minute, while at 30°C ambient temperature the average maximum rate of rewarming was 0.012°C per minute. In addition, higher temperatures had a 2-fold higher relative time index which is defined as the time required to reach maximum rate of rewarming divided by the total arousal duration. Lastly, the interbout arousals increased 5-fold at warmer temperatures, lasting 12 hours at 4°C and 66 hours at 30°C. We interpret these data to suggest high temperature torpor leads to homeostatic issues wherein key processes are poorly coordinated. The result is an inherent increase in variability between individual squirrels and a loss of predictability of key hibernation aspects. NASA TRISH Department of Education NSF. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.