Pronghorn Antelope Migrations

February 19, 2009 by  

By Doug Leier

When the topic is migration, most of us think about birds. Seldom do we associate migration with big game animals, such as moose or elk.

In western North Dakota, however, an ongoing study is shedding some interesting light on a big game species that does migrate. Pronghorns, also commonly called antelope, even though they are not a true antelope, do move around. With the pronghorn hunting season application deadline quickly approaching, it’s a good time to take a closer look at these unique animals.

Historically, North Dakota is on the edge of pronghorn range. The fastest of all land mammals in North America, pronghorns were once common over much of the state, but today most pronghorn are found west and south of the Missouri River, with smaller numbers found in some locales east of the river.

The study began in 2004 when about 60 pronghorn were captured and fitted with radio-collars. More were collared last winter. Research will continue for five years, but even after two years of tracking, biologists are already gaining a better understanding of North Dakota’s pronghorn.

Bruce Stillings, a big game biologist at the Game and Fish Department’s Dickinson district office, is overseeing the project and points to some early realizations. “They’re making much longer movements than we originally thought,” he said. “Sometimes, they’re making large treks in a little over a week.”

As with most animal movements, pronghorn migration is likely predicated on habitat needs during a specific time of year, or is a response to localized changes in food sources, such as heavy snowfall covering available forage.

Stillings cited several instances that shed new light on past theories about pronghorn migration. One involved a 3-year-old buck collared in January 2004 near Beach in Golden Valley County. This animal migrated 130 miles east to near Center in Oliver County that spring, then returned to the Beach area for the summer.

In October the buck headed southwest and actually spent the 2004-05 winter 30 miles into Montana.

Some other notable observations include:

* Of 28 pronghorn collared in Bowman County, 11 were later located via aerial telemetry in Hettinger, Grant, Morton, Stark and Slope counties – and two nearly 25 miles into Montana.

* One of the farthest documented movements by a radio-collared animal from January to June in 2004 was a doe that traveled 115 miles as the crow flies. This pronghorn was captured just north of Rhame in Bowman County and was later located south of New Salem in Morton County.

Malnutrition was determined as the cause of death for five pronghorns that died during winter 2003-04. These animals were wintering in areas where the snow developed a crust in late winter, making it difficult to paw through to reach food. Animals that died of malnutrition did so in late March.

Pronghorn are well distributed through all western counties. Four decades ago there was approximately 14,000. Today, North Dakota has about 15,000.

Biologists have a number of goals for the study, most of which focus on management questions such as seasonal home ranges and distribution of adult pronghorn; habitat use and preference; and survival rates of pronghorn and how they die.

One preliminary finding is that pronghorn movement and migration is limited by highways and fences. Continued research will help biologists determine to what extent these obstacles prevent pronghorn movement. “What we’ve seen so far is that Interstate 94 appears to be a major barrier to winter pronghorn movements,” Stillings said.

What the future holds for pronghorn is unknown, but ongoing research is vital for wildlife managers seeking to answer these and other questions.


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