LIFE-CYCLE CHARACTERISTICS OF NORTHERN PEROMYSCUS-MANICULATUS-BOREALIS

Life cycle characteristics of northern P. m. borealis were examined in the laboratory to identify specific adaptations to strongly seasonal environmental conditions. Although northern P. m. borealis are demographically K selected, body weight (19.2 g), gestation time (26.3 days for postpartum litters), litter size (5.0), birth weight (1.87 g), age at weaning (21.4 days), weight at weaning (9.26 g), growth rates (0.35 g/day) and energy requirements for lactation (181% increase attributable to 5 offspring) are all similar to those of other subspecies of P. maniculatus. General demographic conditions do not appear to have been important in the evolution of the life cycle characteristics of P. maniculatus.