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Accuracy and Precision of Estimating Age of
Gray Wolves by Tooth Wear

Introduction


Noninvasive techniques that are reliable and cost effective are needed to estimate ages of gray wolves. The most widely used technique is counting tooth cementum annuli (Ballard et al. 1995, Landon et al. 1998). This is the only method used to estimate age to the nearest year (Landon et al. 1998), except for marking pups that can later be identified (Mech 1988). To count cementum increments, teeth must be removed, sectioned, and stained. Alternative techniques (Dimmick and Pelton 1994) are needed to avoid injury and to comply with requirements of institutional animal care and use committees at universities, government organizations, and private foundations. Avoiding damage to specimens in museums and private collections is also important (Gipson and Ballard 1998, Gipson et al. 1998). Tooth wear may provide an alternative to cementum annuli aging, but not a replacement for the technique.

Tooth wear has been used to estimate wolf ages (Gipson et al. 1998, Fuller and Keith 1980), but the technique lacks precision and tooth abrasion might vary among regions (Ballard et al. 1995). Landon et al. (1998) examined 4 methods for determining wolf ages and concluded that tooth wear accurately aged pups and older wolves to within 4 years. They described tooth wear characteristics for 5 overlapping age classes and noted that additional study was needed to determine the precision of the technique.

Accurately placing wolves in age categories is important for studies of population dynamics, social organization, systematics, breeding, dispersal, relationships with prey including livestock depredations, and for determining suitability of individual wolves for restoration programs. These studies typically require accurate identification of pups <1 year old, yearlings and young adults 1-3 years old, mature wolves 3-9 years old, and individuals ≥10 years old, but seldom require precision ≤1 year. Our objectives were to determine the accuracy and precision achievable by using tooth wear to estimate wolf age, and to provide criteria for obtaining consistent results.


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