Huddling, locomotor, and nest-building behaviors of furred and furless Siberian hamsters

Rodents living in the cold employ both behavioral and physiological mechanisms to achieve thermoregulation. We examined the impact of fur loss on behavioral thermoregulation in cold-challenged Siberian hamsters (Phodopus sungorus). Intact female hamsters exposed to an ambient temperature (T_a) of 5°C increased their general locomotor activity by 50% relative to animals maintained at 23°C. At both T_a's, fur removal resulted in substantial increases in daily food intake (37% and 22% at 5 and 23°C, respectively) but did not affect the amount of locomotor activity; increased food intake after fur loss evidently is not caused by increases in locomotor activity. Furred hamsters housed in groups of three at 5°C consumed 16% less food per day than did singly housed individuals. Fur removal resulted in identical 39% increases in food intake in group- or singly housed animals. Energy savings that accrued from huddling were identical in furred and furless animals; this behavior conserves energy even in the absence of an insulative pelage. The availability of nesting material resulted in an 18% reduction in food consumption in intact animals kept at 5°C. The increase in food intake produced by fur removal was attenuated by ∼80% when furless animals had access to nesting material. Huddling and nest-building behaviors each ameliorate energetic challenges posed by absence of fur; animals that concurrently employ several modes of thermoregulation realize substantial energy savings in the cold.