Splitting hairs: differentiating juvenile from adult deer (Odocoileus virginianus) by hair width.

This article focuses on developing a quantitative method to distinguish juvenile from adult white-tailed deer (Odocoileus virginianus) hair found in carnivore scat samples by measuring hair width. Using hair samples from captive and vehicle-killed deer in Georgia and Virginia, the study found that hair diameter at 1/8 or 1/4 of the hair length from the follicle reliably differentiates juveniles from adults, with a threshold of 104.2 µm achieving 95.3% accuracy before juveniles undergo their first molt at about five months of age. The research highlights that hair width varies by body location and along the hair strand, and that seasonal molting affects juvenile hair thickness, complicating age classification after mid-September. This method offers a cost-effective, objective tool for assessing age-class in predator diet studies, potentially applicable to other ungulate species and regions, thereby enhancing understanding of predator–prey dynamics.