Rural subdivisions threaten elk, deer, moose and pronghorn by, among other things, preventing them from accessing the best food or escaping harsh weather. Houses, even in the countryside, can be as harmful to migrating wildlife as energy development, highway crossings and fences, according to conservationists and researchers. But while highway dangers can be mitigated with over- and underpasses and fences can be retrofitted to be more wildlife-friendly, researchers didn’t know how much space big game animals require when weaving through rural housing.
Until now.
In a paper published May 11 in the Journal of Applied Ecology, a team of Wyoming-based researchers and biologists outlined generally, and in some cases exactly, how much berth these animals give houses and other buildings.
“We know residential development is a big threat for migration,” said Jill Randall, Wyoming Game and Fish Department’s big game migration coordinator, who was not involved in the study. The new research gives people working on planning and zoning or other building decisions the specific information they need, she said. “We’ve been really lacking that.”
Past research has detailed the harmful effects that human housing — including the fences, roads, dogs and increased traffic associated with it — has on a variety of big game. One study outlined how mule deer hurried through rural housing developments, not stopping for much-needed breaks to rest and eat, while another showed how migrating mule deer avoid densely packed houses. Housing can even be more harmful for migrating mule deer than energy development, according to one 2016 paper.
But none of those studies explain exactly how much space animals need to navigate between houses and other structures. It was with that in mind that University of Wyoming associate professor and migration researcher Jerod Merkle and a team of scientists first sat down with a Microsoft dataset showing the footprint of every building in the Cody and Jackson, Wyoming, areas. They used it to create a grid showing the minimum distance from one house to another.
Then they overlaid hundreds of thousands of elk, mule deer, pronghorn and moose GPS collar data points to visualize how the animals navigated through those spaces. The researchers measured the speed at which the animals moved, evaluating whether they took their time, grazing on grasses, wildflowers or bushes, or hurried through on an apparently fear-fueled mission. The researchers could also see the places they avoided.
“We looked at, in a world where there’s housing everywhere,” Merkle said, “how far away do houses need to be?”
The results are stark.
In rural areas with a structure every 190 acres, on average, wildlife avoided wandering through spaces less than 1.2 miles wide, and never squeezed through spaces narrower than about 150 feet. Animals that were more accustomed to residential development — those used to migrating through suburban areas — meandered into chutes less than a mile wide but still avoided the slimmest paths.
Merkle noted that this doesn’t mean houses must be at least 1 mile apart to accommodate big game migration. Instead, the study supports the idea of developing houses in clusters instead of broadly scattering them across a landscape. Using migration data, a developer could, for example, place 50 houses in a subdivision on 1-acre lots instead of on 5-acre lots, leaving the rest of the property open for migration.
The team also created an interactive map incorporating GPS collar data that allows county planners, landowners and developers to input potential residential lots to see where and how new houses would affect migration.
Concrete data like this can mean the difference between a city council listening to wildlife advocates and ignoring them, said Bettina Cameron, president and co-founder of Eagle Mountain Nature and Wildlife Alliance. She lives in Eagle Mountain City, Utah, one of the fastest-growing cities in the state, and her group has spent years trying to lessen the impact of residential development on migrating mule deer. “When you’re dealing with landowners and legislation and local planners, you need scientific information,” Cameron said. “Without the science, we’re not going to get anywhere.”
“Without the science, we’re not going to get anywhere.”
Both she and Randall acknowledged that not all landowners in the West, a place where many people consider property rights sacred, will follow the guidance. But now, rural landowners who want to do right by wildlife finally have a blueprint to follow.
The research comes with some caveats: The data doesn’t parse the difference between the impact of a rarely used structure like a barn and a busy house with dogs, livestock, fences and other human activity, said Ben Robb, a UW research scientist and the paper’s lead author. Merkle also acknowledged that animals may behave differently in other locations.
But they hope their research, along with the interactive map, will empower planners, developers and even landowners building new homes to also conserve wildlife. After all, robust wildlife populations are what draw many people to rural spaces in the first place.
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