A comparative analysis of huddling in infant Norway rats and Syrian goldenhamsters: Does endothermy modulate behavior?

In infant rats, huddling improves surface-to-volume ratios and provides met abolic savings during cold exposure. It is unclear, however, whether endoth ermy is also a necessary component of huddling. In the present experiment, huddles composed of infant Norway rats (2- or 8-day-olds), which produce he at endogenously, or Syrian golden hamsters (8-day-olds), which do not produ ce heat endogenously, were exposed to decreases in air temperature. Behavio ral and physiological responses were monitored throughout the test. Rats, e specially at 8 days of age, were better able to thermoregulate using huddli ng than hamsters, due in part to endogenous heat production. Furthermore, 8 -day-old rats exhibited behavioral responses that promote heat retention, s uggesting that both physiological and behavioral mechanisms contribute to e ffective thermoregulation during huddling in the cold.