Hair Growth in Brown Bears and Its Application to Ecological Studies on Wild Bears

Hair biomarkers have been widely used to study wildlife physiology and ecology. To apply this technique to practical studies, detailed information on hair growth is needed for each study species. This study measured hair growth patterns, including growth rate, periods of growth and shedding, and hair bulb structural changes in the brown bear. Hair growth was examined monthly in captive bears, and gross observations of fur were performed in wild bears. Guard hairs grew from late April to early October at an approximate rate of 0.5 mm/day for captive bears, and from late May to late September at an approximate rate of 0.7 mm/day for wild bears. Underfur began growing in August and continued into winter. The growth periods for intermediate hairs began at different times and lasted 3–5 months, depending on individuals. Most shedding was complete by August, and all shedding was complete by the end of September. Hair bulbs were classified into three types: white spheres (WS-type), black hooks (BH-type), and white hooks (WH-type). This classification can be used to discriminate between previous year's hair (WS-type) and current year's hair (BH-type or WH-type). The current findings will enhance the understanding of brown bear ecology in the wild.