Shifting strategies for behavioral thermoregulation in developing golden hamsters

Developmental changes in the golden hamster pup's capacity for behavioral temperature regulation were studied. Groups of three pups aged 4-14 days were tested at room temperature (22 degrees C), on a strong gradient (34-22 degrees C), and on a mild gradient (30-22 degrees C). The proportion of time engaged in the following behaviors was recorded: contact with the warm edge (thermotaxis), active huddling, and quiet huddling. Pups tested at 22 degrees C engaged in active huddling, and their temperature dropped rapidly. Only on Day 14 were they able to maintain their temperature constant with a combination of vigorous exploration and quiet huddling. On the strong gradient, by contrast, pups were able to regulate their temperature at all ages. Young pups (4-5 days) depended on thermotaxis rather than huddling, separating when their temperature started to rise. With age, quiet huddling replaced thermotaxis as a dominant behavior. On the mild gradient, pups combined active and quiet huddling with thermotaxis, so that their temperature dropped at al slow steady rate (.1 degrees C/min). It is concluded that hamster pups have a well-developed capacity for behavioral temperature regulation. Whether they attempt to keep their temperature constant or tolerate a slow rate of drop depends on the amount of exogenous heat available, which under natural conditions would be supplied predominantly by the mother. These results suggest that the pups as well as the mother may participate in thermal regulation in the nest.