Pelage cycle in blue fox (Alopex lagopus): A comparison between animals born early and late in the season

Pelage development was compared in male blue foxes born in early May (E) and in early June (L) (4/group). Guard hair and underfur hair cycles were studied histologically on series of skin samples taken from the hip, between August and December. The winter guard hair cycles were similar but there was a shift in time of several weeks between the groups. The difference evened out in mid‐November, when 97% of guard hairs were mature. The growth cycle of winter underfur hairs in group L was more synchronized than in group E. The mean count of mature (telogen) underfur hairs per bundle differed slightly between the groups on 1 December but the mean total hair counts (anagen and telogen hairs) were similar. The natural adjustment of the pelage cycle in blue foxes of different age is modified by the duration of the resting period of summer hair follicles, which probably is mediated via melatonin.