Nipple dimensions and reproductive status of northeastern Minnesota female black bears (Ursus americanus)

Nipple length and width were measured one or more times on 72 female black hears from northeastern Minnesota. An index to nipple volume was calculated, Nipple dimensions and volume for nulliparous bears were relatively constant throughout the year Nipple dimensions and volume for parous, nonlactating and lactating bears fluctuated seasonally. Nipple dimensions of parous bears were considerably larger than those of nulliparous bears, and dimensions of parous, lactating bears were generally larger than those of parous, nonlactating bears. Nipple dimensions could be used to separate nulliparous from parous hears but could only separate nonlactating from lactating parous bears with marginal confidence.