Once they felt free to roam

Movement ecology, a new field, is making it easier to study animals’ migration

HELENA, Mont. — Snow comes early to the Teton mountain range, and when it does, the white-bottomed pronghorn that live here get the urge to move.

Following an ancient rhythm, they migrate more than 200 miles to the south, where the elevation is lower, winter is milder and grass is easier to find. Come the spring green-up, they make the second half of the round trip, returning to Grand Teton National Park.

After thousands of years, biologists are concerned about the future of this migration pattern. While there have been efforts to protect the journey, such as highway overpasses and antelope-friendly fences, some new barriers are looming. Most immediate is the prospect of 3,500 new gas wells planned on federal land at the southern end of the pronghorn’s migratory path. And then there’s the nearby Jonah Natural Gas Field, which is already intensively developed.

“The challenge is understanding how many holes you can punch in the landscape before a migration is lost,” said Matthew Kauffman, a professor of wildlife biology at the University of Wyoming.

Room to move is critical for a wide range of species, but it has long been difficult for researchers to capture where and when they travel.

But a new and growing field called “movement ecology” is casting light on the secretive movements of wildlife and how those habits are changing.

A global study of 57 species of mammals, published in the journal Science, has found that wildlife move far less in landscapes that have been altered by humans, a finding that could have implications for a range of issues, from how well natural systems function to finding ways to protect migratory species.

The large study brought together 114 researchers from across the globe who had gathered information from 803 individual animals. They ranged from the smallest animals that can be collared — pocket mice — to the largest, elephants. Using the GPS collars that updated an animal’s location regularly, the project found that vagility — the ability of an organism to move — declines in areas with human footprints by as much as half to two-thirds the distance than in places where there is little or no human activity.

“It is important that animals move, because in moving they carry out important ecological functions like transporting nutrients and seeds between different areas,” said Marlee Tucker, a biologist at Senckenberg Biodiversity and Climate Research Center and Goethe University, Frankfurt and the study’s lead author.

There has been exponential growth in data on wildlife movement as technology has evolved,. “We used to have one dot on a map twice a day,” said Roland Kays, a biologist at North Carolina State University who participated in the study. “Now we have a point as much as every second and know exactly where they are going, how they are avoiding people, how they are crossing the road and catching prey. It’s big for determining how animals die or where they die and how that affects populations.”