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Study: Human development can block antelope migration

Posted at 11:00 AM, Dec 31, 2020

MISSOULA — Conservationists know the most important thing to do for wildlife is to protect their habitat. Now, research shows good habitat is just as important in regions where wildlife migrate.

Earlier this month, eight scientists published an eight-year study emphasizing the need to protect large swaths of prairie in eastern Montana and Canada from more development, so pronghorn antelope can continue their historic spring and fall migrations.

Antelope migration routes can extend hundreds of miles, crossing various property lines and international boundaries, so it’s clear more cooperation among a wide variety of landowners is needed.

Using helicopters and gun-launched nets, the biologists captured and successfully collared 173 antelope during the winters of 2003 through 2010. They used GPS collars capable of recording accurate location information every two hours instead of just once a day.

More than half the antelope they collared were migratory – not all antelope are – and the scientists used their data to identify where the animals went and what habitat was present along their preferred routes.

Lead researcher Andrew Jakes, a National Wildlife Federation biologist in Missoula, said advances in tracking technology allowed the biologists to follow their study antelope more closely than before to learn how the animals choose their routes.

“Our findings affirmed the importance of open grassland and sagebrush habitats as important migration habitat. We could also document the extent to which natural changing conditions, such as foraging quality, and human-created features, such as road density and fossil fuel infrastructure – i.e., oil and gas wells – shape pronghorn migration routes,” Jakes said in a release.

The researchers included five other Montana scientists from Montana Fish, Wildlife & Parks, the World Wildlife Fund and the University of Montana. The Canadian scientists were from the University of Calgary and the Alberta Conservation Association.

“What this research has highlighted is how pronghorn are indicative of how wildlife try to eke out a living on a highly fragmented landscape and that jurisdictional boundaries are just lines on a piece of paper. It also shows that pronghorn at the northern periphery of their range are sitting on the edge of a precipice ready to fall off if we lose these migration routes and they are no longer able to move in response to fluctuating conditions,” said Alberta Conservation Association biologist Paul Jones.

Using highly detailed maps of prairie vegetation and human development including roads, oil wells and farmland in northern Montana and southern Canada, they found the antelope avoided features of human disturbance above all else when choosing their overall route from start to finish.

“Our results showing avoidance of roads during both migratory seasons are consistent with others that suggest roads, and the accompanying high-vehicle densities and speeds on primary and secondary roads, may act to fragment the landscape more than any other measured factor,” the group concluded.

Once the antelope are on their way, however, there’s not much they can do when they run into risky spots. So they will travel across developed areas such as well pads. But not surprisingly, they did so quickly. And if they have to do that too much, they experience more stress.

The researchers found a difference between spring and fall migration routes when it comes to habitat preference. In the spring, antelope will try to move between areas that provide high-quality forage, especially as plants are “greening up” on the herd’s trek north.

That’s likely because the animals are trying to recover from a lean winter and their young need the nourishment. Native grasses contain more protein than crops so antelope eat better when they can travel on healthy, undeveloped land.

Conversely, in the fall, antelope have fattened up and don’t need to worry as much about finding food. Plus, fall weather can be more unpredictable with sudden cold snaps. So antelope travel faster and use a more direct route during their fall migration, trying to reach their wintering grounds before snow really sets in. While they still avoid human development, they tend to follow exposed ridges lines along major rivers that tend to stay snow-free to find their way home.

So human development in the wrong places is a problem for antelope or any species that uses migration. In Montana, it didn’t used to be so. But now, as more people move to the West and replace once-natural landscapes with more buildings and roads and as extractive industries lock up public lands, it’s becoming ever more urgent to find and protect the lands that wildlife need before they’re gone.

A World Wildlife Fund report released in September showed that human activities in just the last 50 years have caused the world’s wildlife populations to plummet by more than two-thirds.

That knowledge is part of what spurred a group of hunting, conservation and private landowner organizations to urge FWP to develop a new wildlife movement and migration strategy, published less than a month ago after a year’s worth of work.

It came out of the recognition that the state is changing fast so FWP programs need to prioritize solutions that protect wildlife movements. The strategy also recognizes that farm and ranch owners can play just as big a part as public land managers in keeping migration corridors open.

For example, conventional barbed-wired fences are a notorious problem for antelope, which are great at running but not so much at jumping. They will try crawling under but often die tangled up on such fences.

Conservation organizations encourage landowners to replace barbed wire with slick wire strung farther above the ground. But with miles of barbed wire weaving across the prairie and more landowners to convince, it’s a slow process.

The findings in this study will provide a better idea of what kind of places antelope need during their migrations so land and wildlife managers know where to focus conservation efforts. The information is essential because they’re running out of time.

“Our paper is a great example of the need for Montana Fish, Wildlife and Parks’ recently released wildlife movement and migration strategy to help conserve migratory species, like pronghorn, here in Montana,” said UM wildlife biology professor and study author Mark Hebblewhite.