WINTER ACCLIMATIZATION IN PEROMYSCUS-MANICULATUS-GRACILIS, P LEUCOPUS-NOVEBORACENSIS, AND P L LEUCOPUS

Peromyscus leucopus noveboracensis and P. maniculatus gracilis indigenous to New York and P. l. leucopus obtained from North Carolina were assessed for traits assumed to enhance winter survivorship; including torpor, nesting behavior, food hoarding, and seasonal molting and breeding. The typically montane-adapted P. m. gracilis exhibited the most pronounced physiological and behavioral changes in response to winter, with P. l. noveboracensis and P. l. leucopus respectively exhibiting lesser degrees of these adjustments. In all mice, occurrence of torpor was confined to winter months. During mid-winter, nearly 40% of P. m. gracilis became torpid, contrasted with 15-20% and 10% of P. l. noveboracensis and P. l. leucopus, respectively. P. m. gracilis constructed larger nests and demonstrated a greater propensity to hoard food, and the percentages of mice that became reproductively regressed and that molted to winter pelage also were higher in P. m. gracilis than in the two subspecies of P. leucopus. Furthermore, P. m. gracilis consistently expressed these adaptations during a longer period of time than the other Peromyscus. While P. l. leucopus from North Carolina exhibited less pronounced seasonal adjustments than their more northern conspecifics, exposure to winter conditions in northern New York enhanced their adaptive response relative to mice at their native latitude. Of particular interest was our finding that the winter adaptive response in P. m. gracilis resulted in lower daily food consumption than observed in either of the subspecies of P. leucopus.