click on the image to view the mapped satellite data (1985-1990)

By late March, pregnant cows move onto high ridges and begin their northward migration from the wintering range to spring calving grounds. They follow either ridges (in deep snow years) or river valleys, reaching the calving grounds by late May. Once above treeline the animals are on their worst range conditions. Lichens, which have sustained them throughout the winter, are scarce above treeline and new growth has not yet begun.