Mulies on the move

Scientists discover a surprising migration in western Wyoming.

  • Mule deer are one of the West's most common species, but only recently has modern technology allowed humans to piece together their movements across the landscape, including a 300-mile round-trip migration route in western Wyoming. All summer these deer gorge on forbs and grasses in the Gros Ventre Mountains. Come fall, they must leave or risk getting trapped in building snowpack.

    Joe Riis
  • A map shows the mule deer migration path, covering a 300 mile round-trip through western Wyoming

    © 2014 Atlas of Wildlife Migration: Wyoming's Ungulates
  • Along their journey, they splash through Pine Creek in a narrow spot between Pinedale, Wyoming, and Fremont Lake.

    Joe Riis
  • A doe glances at a camera trap at one of many creek and lake crossings along the migration path.

    Joe Riis
  • A young buck mule deer navigating an elk fence. Deer can't clear the high elk fences, which are designed to keep elk off private land.

    Joe Riis
  • A herd of migrating mule deer skirts along a residential area in the Upper Green River basin.

    Joe Riis
  • By winter's end, the deer have been losing weight for months and are nearly starved. Their journey back to the mountains helps them make the most of Wyoming's short growing season and put on fat to survive the next winter.

    Joe Riis
  • A herd of mule deer shakes off after crossing the Fremont Lake outlet just north of the town of Pinedale.

    Joe Riis
  • A doe mule deer crosses a road at the southern end of Fremont Lake near Pinedale. This area is a pinch point for many deer.

    Joe Riis
  • Three buck mule deer in their summer range, above 10,000 feet in the Hoback Mountains.

    Joe Riis
  • A mule deer buck migrating south through boulder fields in the foothills of the Wind River Mountains, just east of the town of Farson, Wyoming.

    Joe Riis
  • A large buck picks his way along an elk fence looking for a way through. Eventually, the deer get into rolling sagebrush along the Wind River foothills and head south toward their Red Desert winter range.

    Joe Riis
  • A herd of mule deer on the move. They often travel in early morning and evening, and sometimes at night.

    Joe Riis