“Ability of the Ground Squirrel, Citellus Lateralis, to Be Habituated to Stimuli While in Hibernation”, 1968-08-20 (; similar):
The animals used were golden-mantled ground squirrels, Citellus lateralis, whose hibernating behavior had previously been well studied…
…After the regular 12–14-day pattern of continuous hibernation had been established, several hibernating animals were removed from their nests, tossed once 2 to 3 ft in the air, caught, returned to their nests and the sawdust replaced in a pyramid on their dorsal surface. Such a stimulus invariably caused the animals to arouse as evidenced by observing them in the state of arousal some hours later or by the absence on the following day of the sawdust, which was then replaced on the animal that had re-entered hibernation.
Using this procedure animals were stimulated daily until it was found that they responded to such a stimulus by not arousing until the next normal arousal was due. This clearly indicated that the animals were being habituated to the tactile stimulus while in hibernation, and subsequently the daily “tossings” were increased gradually until it became possible to repeat this procedure 100× without causing the animal to arouse from hibernation.
Admittedly this experiment is “crude”, and in future studies the more accurately controllable electrical stimulus will be used. Nevertheless, the results are conclusive enough to establish the fact that with a body temperature as low as 1℃, the nervous system of these hibernating mammals is fully functional even to the point of establishing a habituated response to stimuli.