The calf, weighing 5-9 kg at birth, follows its mother within an hour of its birth, and is capable of outrunning a human by the time it is a day old. The young nurse exclusively for about one month, then occasionally until winter comes. Wild caribou reach sexual maturity at 29-41 months of age. Behavior Caribou are diurnal and gregarious. They form large herds of up to 200,000 animals, but they are typically found in subgroups of 10-1,000 animals.
Caribou are remarkable for thier extensive migrations.
Because of the severe climate of their arctic habitat, caribou migrate to lower latitudes or elevations before winter comes. A herd's range may shift by as much as 1000 km before winter. This range shift is typically abrupt, with herds moving from 19-55 km per day. During the migration, the density of animals may reach as many as 19,000 animals per square kilometer. Caribou are reputed to have poor eyesight, and they are thought to locate food items using their keen sense of smell.