The Relationship of Nest Protection and Huddling to Survival of Peromyscus at Low Temperature

Abstract

It seems obvious that the degree of protection offered by nests during winter must be an important factor influencing the survival of small mammals during periods of extreme cold when they are not actively searching for food. Absence of suitable nesting material, lack of natural hiding places, or inability to burrow below the surface would allow the full effect of low temperature to be exerted more drastically and might well be maj or factors contributing to winter mortality in the absence of other protective mechanisms. Although the protection afforded by the nest probably prolongs survival at all temperatures below that of thermal neutrality its effectiveness is perhaps greatest at extreme low temperatures when prevention of excessive heat loss is most vital for conserving energy reserves. Huddling of mice in groups of two or more individuals must also play a not inconsiderable part in prolonging survival at low temperatures. When combined with nest protection the resistance to low temperature might be enhanced still more by a summation effect. Richter (1942) reported that thyroidectomized or hypophysectomized rats, which have limited physiological means of maintaining normal body temperature, build large nests in an attempt to conserve their heat. He also emphasizes (Richter 1927) the importance of other thermo-regulatory activities of the rat such as burrowing, huddling into small spaces, and huddling together in conserving body heat. In a study of nest-building activity of the albino rat, Kinder (1927) exposed