Bull dominance hierarchy in rut. Results in short calving period. Natural mortality factors may be high- wolves, lynx, bears, accidents. In Alaska, wolves are being controlled in a few districts to reduce mortality on hunted populations of caribou. This practice is controversial, but does result in higher caribou population.
Lichens are low in protein, but high in carbohydrates.
Caribou rumen bacteria ferments the carbos, producing ammonia, which aids in recycling nitrogen, thus compensating for low protein. In summer, Caribou utilize a wide variety of vegetation- grasses, sedges, forbs and browse. Caribou hoof is wide, and dew claws are large. Pad under hoof thickens in summer for support on muskeg, but thins out in winter making hoof sharp edged for ice traction. Several attempts have been made in various areas, mixed results.