lifecycle
The Caribou Life Cycle
Caribou move restlessly year round. Pregnant females travel the greatest distances. In spring, they head north. Small groups combine into larger herds as they near their calving grounds. There, in the first weeks of June, most calves are born. At birth, calves weigh about 6 kg, but they can soon stand and nurse. Within days they can follow their mothers as they wander the tundra to feed.
Bull caribou and barren females tend to gather in loose groups south of the calving grounds. All caribou spend the summer grazing to build up much needed fat for the return migration and the rut. During August and September, they must be in peak condition before the long winter. Once they mate in late September and October, many barren-ground caribou will winter in small groups in lichen-rich open forest.
The health of a caribou herd is largely dependent on the health of the females. Mature females lead the herds north to calving grounds and south again to winter protection. Knowledgeable hunters permit the leaders of a herd to pass, to ensure younger members of a herd learn where to cross lakes and rivers and where good grazing can be found.
Females give birth to a single calf, starting in their third year. A cow may bear six or more calves over her lifetime. If half survive, and half are female, then another one or two breeding females are added to the herd. Weather plays a huge part in the herd’s good health. A late spring ice storm on the calving grounds can wipe out a generation of baby calves and leave the females weakened and vulnerable to predators.
Caribou can live up to 15 years. The largest bulls with their massive racks are probably in this age range. But caribou often die early, too. They might sprain a leg and not be able to outrun a pack of wolves. Some may be swept away trying to cross a raging river. Bulls can lock antlers with younger rivals, and both will starve.
When there are plenty of healthy calves each year for a number of years, a herd can withstand some natural losses, and numbers of caribou can increase.
