No one expected to make a record-breaking discovery when they set out to study a herd of mule deer in Wyoming, but when scientists took a closer look they found an extraordinary migration hiding in plain site.
The discovery is the result of work that began in 2011 when wildlife researcher Hall Sawyer put GPS-radio collars on members of a herd of deer who were thought to be a non-migratory resident herd that the Bureau of Land Management wanted more information about.
Sawyer and other scientists from the University of Wyoming were surprised to learn that these mule deer travel 150 miles from their winter grounds in the Red Desert to the Hoback Basin as they follow the emergence of fresh green plants along routes that have been passed down through generations.
Their journey is described in a detailed report that chronicles their adventures, which was produced by the Wyoming Migration Initiative. Scientists involved in the initiative are now examining movements of migratory ungulates in the state, including pronghorn, elk, moose and bighorn sheep:
In spring, an estimated 500 deer travel 50 miles north across the desert to the west side of the Wind River Range. From there, they merge with 4,000 to 5,000 other deer that winter in the foothills of the Wind River Range and then travel a narrow corridor along the base of the Winds for 60 miles before crossing the upper Green River Basin. In the final leg of the journey, they travel another 30-50 miles to their individual summer ranges in the Hoback Basin.
Their migration is now believed to be the farthest recorded mule deer migration in the world and longest land mammal migration in the lower 48, beating out the pronghorn antelope’s current record of more than 100 miles as they travel from the Grand Teton National Park to Wyoming’s Upper Green River Basin.
For mule deer, whose populations are dropping in Wyoming, the discovery is well timed. While the mileage alone might not seem that great, the mule deer’s trek across unprotected public and private lands leaves them facing many natural and man-made challenges and obstacles to get past, including highways, subdivisions, about 100 fences they have to go over, under or around, along with reservoirs and rivers to cross.
In one area near the Finger Lakes, their route has been reduced to a narrow bottleneck just 50 meters wide as they move between elk fencing and a campground. In the south, I-80 has completely blocked their movement and is believed to have caused many to die by preventing them from reaching areas where they can forage in the winter.
Sawyer told National Geographic that he hopes showing people what the deer go through during their migration will help motivate us to help make their journey a little easier.
He added that if we want to help mule deer, and other ungulates survive, we need to protect these migration routes, but that it will be a challenge considering they span a mix of federal, state and public lands. There are however things that can be done now to help them pass, including taking down unnecessary fencing and using gates that can be left open for them.
More importantly, knowing where migration corridors and stopover points are can be used to help with future land use decisions.
The Wyoming Migration Initiative is now working on an “Atlas of Wildlife Migration” that details all of the state’s ungulate migrations, in addition to creating an online database to make migration data widely available to a range of interested stakeholders from land managers and energy companies to conservation organizations and the public.
Wildlife photographer Joe Riis also captured some amazing images and footage that were compiled to help raise public awareness and offer us a view of the journey these deer complete in the spring and fall.
For more information on the work these scientists are doing, visit migrationinitiative.org.
Photo credit: Thinkstock