Thermal environment affects hair coat development of Norway rats

Abstract Newborn rats have limited homeothermic capabilities and little insulation. Nevertheless, rats flourish in diverse thermal environments. We hypothesized that the environmental temperature influences the development of their hair coat insulation. Rats were housed from birth (0 d) in either a cool (17 °C), moderate (25 °C), or warm (33 °C) environment. Measures were recorded from young juveniles (22 d), old juveniles (43 d), and young adults (85 d). Cool-housed rats were found to develop greater body and coat mass and a higher coat mass to body mass ratio than warm-reared rats. These results indicate that thermal environment affects the growth of the hair coat insulation of developing rats.