During the winter, this gregarious deer roams about in large herds of up to 300 individuals (3) (4). With the arrival of summer, these herds break up and move to higher elevations where they roam less and stay for longer periods, grazing in the rich alpine meadows on grasses, sedges, alpine forbs, and occasionally foliage from shrubs (3). These meadows are often situated below large, rocky ridges, which the Thorold's deer may move up into to escape predators if need be (3). With the return of cold weather in September, the males and females will descend to their winter range, in time for the mating season. The rut lasts for around 80 days, between late September and the end of December (3). During this period, the males can become highly aggressive (2), and will display with high-pitched bellows and thrashes of their antlers (2) (3), sometimes resulting in sparring or serious fighting (2). After the rut, the old males depart from the herd, leaving the females with the young males (3). Calving takes place between late May and early June (4), when pregnant females segregate themselves from the group and give birth in hiding (3). The new born calf remains hidden on high ridges, or at the edge of forest, whilst they grow rapidly; the mother remains nearby, very alert, and visits the young frequently for suckling (3).