Thermal environment affects morphological and behavioral development of Rattus norvegicus

Norway rats are widely distributed throughout diverse climates from the tropics to the arctic. As a result, the environmental air temperature experienced during postnatal life varies widely and should influence the development of body morphology and thermal preference. To quantify this relation, rats were housed from birth to adulthood in cool (17 degrees C), moderate (25 degrees C), and warm (33 degrees C) environments. Body morphology measures were recorded weekly and thermal preferences were assessed every 3 weeks. Compared to moderate-housed rats, cool-housed rats developed shorter ears, shorter tails, and a lower tail-length to body-length ratio. Warm-housed rats developed less mass, shorter bodies, and a higher tail-length to body-length ratio than moderate-housed rats. By postnatal day 42, cool-housed rats established and then maintained a preference for warmer air temperatures and warm-housed rats established and then maintained a preference for cooler air temperatures. These results quantify morphological and behavioral developmental plasticity by the Norway rat in response to the thermal environment.