Wolf nipple measurements as indices of age and breeding status

We measured nipple sizes of 29 captive wolves (Canis lupus), of known breeding histories, throughout the year and tested distinctions among various known breeding statuses of 20 wild wolves examined in northeastern Minnesota from May through September. For ca. 8 mo of the year only breeders and nonbreeders can be classified. Distinctions between current and former breeders were not reliable.