Hair Growth Rate Estimation in North American Ursids

The study examined hair growth rates in North American bears using dye/bleach and isotopically labelled glycine methods, involving 3 black bears, 1 polar bear, and 3 grizzly bears in zoos. Over 5 months, hair samples were collected weekly or bi-weekly, revealing that both methods effectively tracked individual and seasonal variations in growth rates. Polar bears showed growth rates of 0.34–0.84 mm/day, black bears 0.10–0.67 mm/day, and grizzly bears 0.53–1.05 mm/day. The research highlighted the importance of non-invasive techniques and provided insights into bear ecology, emphasizing the need to consider seasonality in ecological studies using hair samples.