Thermoregulatory behavior in rat pups from birth to weaning

One–19 day old rat pups were placed individually in a thermal gradient (floor temperatures 17–45°C) at either 45°, 30°, or 20°C. From the first day of life, pups placed at 45° or 30°C and given sufficient time (up to 2 hrs) oriented and moved along the gradient to an area of moderate temperatures (35°–40°C). The pups regulated their body temperatures by remaining in appropriate positions in the gradient. Most pups under a week old were immobilized when placed in the cold area. During the next two weeks, pups placed at 20°C moved up the gradient to the 35°–40°C area. Response latency was related to both starting temperature and age. Observations of the pups' behavior in different temperatures are discussed.