Foot loadings and pad and track widths of Yellowstone grizzly bears

I used measurements of grizzly bears (Ursus arctos horribilis) from the Yellowstone region, USA, to investigate relationships between widths of foot pads and widths of tracks, foot loading and pad size, incidence of tracks and type of activity and widths of front-foot pads and gender and age-class. Track width was affected by substrates and increased relative to pad width as sizes of both pads and tracks increased. Foot loading (kg . cm(-2)) did not vary substantially with foot size and so did not explain the proportionately larger tracks of larger animals. Tracks were most commonly associated with feeding activity that entailed excavation of fossorial foods (roots and rodents); they were least common when bears were feeding in the forest, feeding on ungulates, or traveling. Adult males and females could be differentiated by the width of their front-foot pads. Virtually all pads > 14.5 cm wide belonged to adult or large subadult males. The pads of subadult females were most commonly < 12.5 cm wide, whereas those of adult females were most commonly 12.5-14.5 cm wide.