Evaluating the accuracy of ages obtained by two methods for Montana ungulates

We evaluated the accuracy of ages assigned by Matson's Laboratory from examination of annuli in the cementum of incisor root tips of 111 known-age Rocky Mountain elk (Cervus elaphus), 108 known-age mule deer (Odocoileus hemionus), and 74 known-age white-tailed deer (Odocoileus virginianus). Accuracy rates were 97.3% for elk through age 14, 92.6% for mule deer through age 14, and 85.1% for white-tailed deer through 9 years old. There was no pattern of error relative to age. Accuracy for a sample of known-age mandibles aged by eruption-wear criteria was lower for mule deer (62.3%) and white-tailed deer (42.9%) than accuracy of ages in subsequent samples determined from cementum analysis of incisors. Accuracy of ages of elk assigned at check stations by eruption-wear criteria was >50% only for age classes 3 and 4, and averaged 16% for elk greater than or equal to 5 years old. Ages assigned by eruption-wear criteria were not reliable for comparing physical measurements and population parameters by age among populations. Further, errors in ages assigned by eruption-wear in one age class were not equally balanced by offsetting errors in assigned ages among other age classes. This resulted in inaccurate estimates of population age structure when ages were assigned by eruption-wear criteria. The accuracy provided by the cementum annuli method is necessary to determine whether various physical and population parameters change significantly with age of the animal.