Estimating Age and Antler Traits of Photographed Male White-tailed Deer
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Antler measurements are used to set harvest restrictions for male white-tailed deer (Odocoileus virginianus) and to evaluate response to management. Remotely-triggered trail cameras are popular research and management tools, but have not been used to estimate antler size or age. We developed methods to estimate antler measurements and age of male deer ? 1 year old from photographs. We developed predictive equations for individual antler measurements using photographs of mounted deer heads, and evaluated five anatomical features for potential use as a known-sized scaling reference in field photos. Mean estimation error for individual antler characteristics of free-ranging deer ranged from 6.7% for tine length to 19.3% for length of non-typical points. Mean estimation error for gross Boone and Crockett antler score from a single photograph was ? 5.9%, and was improved by using multiple angles. To develop age-predicting models, we evaluated 64 morphometric ratios derived from photographed, captive, known-age males, retaining 12 ratios to develop multi-step models for pre- and post-breeding application. Accuracy of the multi-step models for assigning 1.5-, 2.5-, 3.5-, 4.5-, and ? 5.5-year-old age classes during pre-breeding was 75%, 86%, 40%, 0%, and 71%, respectively, and 88%, 71%, 53%, 14%, and 85%, respectively, during post-breeding. Accuracy of many age group combinations may be sufficient for management application. Remotely-triggered cameras paired with antler- and age-estimating predictive models would allow non-lethal collection of data from un-harvested deer with acceptable accuracy and less bias than hunter-harvested or visual observation samples.
