Pelage and molt in the black-tailed deer (<i>Odocoileus hemionus</i> (Rafinesque))

Abstract

The pelage of the black-tailed deer (Odocoileus hemionus) has been studied through the year using skin biopsies taken from young and mature individuals. Four pelages, natal, juvenile, adult summer, and adult winter are grown. Six types of hairs are identified and the annual cycle of the follicles producing the four types found in the adult animal is described.This species molts twice annually. The spring molt involves guard hair follicles only, with the undercoat shed by breakage. The autumn molt involves all follicles. The long guard hairs have a sensory function.The guard hairs increase in diameter progressively from birth to adult winter pelage. They are longest in the adult summer pelage, which also has the greatest difference between body areas in length and thickness of the hair. The fawn birth coat is the simplest, the adult winter pelage the most complex.Length–diameter regressions of the guard hairs through the four pelages reveal a steady progression.Study of the color banding of the hair in the four pelages, and upon five body regions revealed constant differences in the component contributed by each of four color zones. The hairs of the five body regions differ most in color in the fawn pelage and least in the adult pelage.Strong inference points to the same follicle as the source of the distinctively different summer and winter hairs, as well as of the age sequence found in the hair.Samples of guard hairs from O. h. sitkensis and from California and Vancouver Island specimens of O. h. columbianus showed significant differences between the three stocks in the length–diameter relationships of the hairs grown by each of these stocks.