Maturational Molts and Seasonal Molts in Peromyscus boylii

Abstract

The time and sequence of maturational molts for Peromyscus boylii were documented in the laboratory and an approxi- rnate age classification developed. The mode of duration of the juvenile pelage was five weeks; subadult pelages, seven weeks; young adult pelage, three weeks; intermediate pelage, seven weeks; and the fully adult pelage followed indefinitely. Two annual adult molts were recorded in natural populations of the brush mouse; one in spring and a second in fall. The summer and winter pelages were distinguished on the basis of color dif- ferences. In natural populations of the brush mouse the youngest animals observed to be sexually active were in the subadult pelage. The correlation of a mammal's age to the color and type of pelage it possesses is a useful factor in many types of field and laboratory research. The molts of several species in the genus Peromyscus have been studied by various workers. Collins (1923) and Blair (1940) recognized four age groups of Peromyscus maniculatus based on pelage: juvenile, subadult, young adult, and adult. The maturational molts of Peromyscus truei and P. calif ornicus were recorded and compared by McCabe and Blanchard (1950); the postjuvenile molt of Peromyscus leucopus was studied by Gottschang (1956); and information concerning the molts of Peromyscus gossypinus was con- tributed by Pournelle (1952). Mice of the genus Peromyscus are generally considered to undergo