Evaluation of a formula that categorizes female gray wolf breeding status by nipple size

Northeastern Naturalist
By:  and 



The proportion by age class of wild Canis lupus (Gray Wolf) females that reproduce in any given year remains unclear; thus, we evaluated the applicability to our long-term (1972–2013) data set of the Mech et al. (1993) formula that categorizes female Gray Wolf breeding status by nipple size and time of year. We used the formula to classify Gray Wolves from 68 capture events into 4 categories (yearling, adult non-breeder, former breeder, current breeder). To address issues with small sample size and variance, we created an ambiguity index to allow some Gray Wolves to be classed into 2 categories. We classified 20 nipple measurements ambiguously: 16 current or former breeder, 3 former or adult non-breeder, and 1 yearling or adult non-breeder. The formula unambiguously classified 48 (71%) of the nipple measurements; based on supplemental field evidence, at least 5 (10%) of these were incorrect. When used in conjunction with an ambiguity index we developed and with corrections made for classifications involving very large nipples, and supplemented with available field evidence, the Mech et al. (1993) formula provided reasonably reliable classification of breeding status in wild female Gray Wolves.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Evaluation of a formula that categorizes female gray wolf breeding status by nipple size
Series title Northeastern Naturalist
DOI 10.1656/045.022.0402
Volume 22
Issue 4
Year Published 2015
Language English
Publisher Northeastern Naturalist
Contributing office(s) Northern Prairie Wildlife Research Center
Description 6 p.
First page 652
Last page 657
Country United States
State Minnesota
Other Geospatial Superior National Forest
Online Only (Y/N) N
Additional Online Files (Y/N) N
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