Deer Ages from Teeth: Agreement, Accuracy and Missed Years

Separating yearlings from adults produces the strongest agreement between jawbone estimates and cementum readings. Pinning an adult to a particular year proves harder: roughly 85% was the ceiling for exact-year accuracy among the methods tested here. Trials involving deer of documented age in southern Texas put jawbone accuracy at around half or below for adults. Cementum performed better, but still missed exact ages. Our calculation shows that jawbone and cementum estimates assigned 1,292 Iowa bucks to matching yearling-or-adult categories about 90% of the time. Our search turned up no test comparing hunter-submitted ages with documented ages.

An aging method gets a fair assessment only when tested against deer whose actual ages are documented. According to its authors, the largest published sample of adult whitetails with documented ages comes from southern Texas. There, Foley and colleagues tracked animals first marked during their fawn or yearling years until hunters harvested them. Six practiced readers examined 264 jawbones representing 134 deer of both sexes. Depending on the reader, exact-year accuracy ranged from 43 to 51%. Those six readers returned identical ages on just 19% of jaws. Accept estimates within a year, and accuracy rises to 87%. For cementum aging, a laboratory counts yearly rings visible in a section of an incisor's root. That method achieved 60 to 62% exact-year accuracy and 93% accuracy with a year's allowance.

Jawbone results from other documented-age trials are similar. In research from Montana, whitetail jaws yielded 42.9% exact-age accuracy. Foley's group also gives 40% as the result of an earlier trial conducted by Gee and colleagues. Cementum results varied more. Montana's sample included 74 whitetails of documented age, extending through age 9, and achieved 85.1% accuracy; Texas achieved 60 to 62%. Foley's group notes that cementum rings may be difficult to distinguish in regions with mild winters and little seasonal variation, including southern Texas, so accuracy may differ among regions. Research by Adams and Blanchong also references 34 Mississippi deer with documented ages: jaws correctly aged all 34, while cementum achieved 76% accuracy. Because we could not access that original study to check the animals' ages, we excluded its results from the chart.

For 1,292 bucks harvested in Iowa during 2014 to 2018, Adams and Blanchong compared estimates from jawbones with cementum readings. State employees, university technicians and the authors estimated ages from jawbones during fieldwork, at meat-processing facilities and in laboratory settings. Cementum matched the jawbone yearling designation in 80% of cases. Agreement reached 65% among bucks assigned age 2 from jaws and 78% among those assigned age 3 or above. The researchers anticipated the strongest match among yearlings. That designation depends on tooth eruption, whereas estimating older ages requires interpreting wear. The study uses age at the most recent birthday; its age 2 therefore describes a 2.5-year-old during fall.

Combining age 2 with animals age 3 or above changes the result. We calculated from Table 4 in the study that cementum classified as adults 94% of the 870 bucks assigned to adulthood from jaws. Across the full sample of 1,292 bucks, roughly 90% matched categories under this broader division. The researchers offer similar guidance: managers using jawbones should separate yearlings from deer aged 2 or above. Subjective judgments about older animals can distort the age structure reconstructed from those estimates.

One out of five bucks classified as yearlings from jaws received an older cementum age. The researchers caution that the error could come from either technique. They also explain that a permanent tooth freshly erupted late in fall can lead a reader to assign an older age.

For 473 deer in the Iowa sample, two incisors from each animal were submitted individually to the laboratory. Readings disagreed for 89 animals, or 19%. Of those mismatches, 84 out of 89 were separated by a single year. Our count therefore puts 99% of paired readings within a year of each other. The 99% compares cementum readings with other cementum readings. It describes precision without establishing how near either estimate was to actual age. The laboratory assigns letters to express confidence in its readings. A tooth rated below the highest confidence category appeared in 104 out of 473 pairs, or 22%. Agreement declined with confidence grade, so readers should place less weight on ages carrying lower grades.

Foley's group also examined jawbone estimates alongside cementum readings for bucks taken at one large ranch in Texas. Among bucks assigned age 6 from jaws, cementum placed 32% at ages 7 to 16. For bucks assigned age 7 from jaws, 35% received cementum ages of 8 to 12. The study also reports a tendency for cementum to underestimate older animals, meaning their actual ages could be higher still. Within the documented-age sample, jawbone estimates matched grouped categories for 79% of age-2 animals. Accuracy dropped to 48% for ages 3 to 5, then to 28% for animals age 6 or above. Tables built from jawbone readings can consequently understate the oldest bucks. Comparing such a table with another state's cementum results reflects differences between aging methods just as much as differences between herds.

The table below groups seven claims found in harvest reports according to the support they receive from the tests.

Our the Golden Triangle uses “mature buck” for a male assigned to the Illinois DNR category of 2.5-year-and-older deer. This corresponds to adulthood in the preceding table, the division supported by these tests. We have yet to establish the process Illinois uses to make that assignment. Both the state's 2021-22 summary and its summary for 2024-25 describe age classification using hunter-submitted morphological information for deer entered through the automated reporting system. With that process, the adult category accounted for 64.1% of antlered bucks reported in 2024; yearlings accounted for 35.9%. Our search found no trial testing hunter-submitted ages against documented ages. The county-level series used in our analysis might also originate from records different from those behind the published summary. Accordingly, “mature” identifies a category in that analysis rather than an age established by measurement. Our tables contain no whitetail harvest-age data, leaving this article without a separate county chart.

Trials using documented ages involved southern Texas and Montana herds. Iowa's comparison instead pairs methods that can both make mistakes. These rates do not necessarily carry over to deer in another state, deer with a different diet or readings by a different grader. Iowa's jawbone estimates were assigned by employees and technicians; these results do not validate hunter-submitted ages. Accessible abstracts omitted sample sizes for some jawbone results, so we compared studies individually instead of averaging their rates. We retain each study's age designations, based on the most recent birthday. The table behind our calculated estimates of 94% and 90% was rounded to two places, leaving roughly half a point of rounding error. Published counts supplied the basis for our 99% calculation.

The category attached to a harvest-report age determines how useful it is. Base decisions on the categories fawn, yearling and adult. Treat a particular adult age as a range. Texas trials placed jawbone estimates within a year of documented age for 87% of mandibles. Cementum estimates met that allowance for 93% of incisors. Remaining estimates missed by a larger margin. Comparisons of old-buck proportions across states should start with the aging technique behind each result. Three questions help assess an age table quickly. Did the estimate come from jawbone examination, laboratory analysis or information supplied by a hunter? Does the table combine adults or divide them into narrower ages? If the age came from a laboratory, which confidence grade accompanied it?