When cold weather comes to the park, thousands of elk migrate to the lowlands to find softer snow and food under it. The annual winter migration starts in late October and lasts till December and takes the herds out of the park territory to various refuges.
Winter is the season when they can become food for predators, maybe understanding this they keep on moving towards their winter shelters. In April and May they make their way back to higher elevations and park borders. Calves are born in protected areas during the spring migration in late May and June.
This is the natural cycle. The migration of this super herd is one of the most exciting and studied phenomenons in the park.