New Research Spotlights Mule Deer

“We’re giving them a better chance to survive in an ever-changing landscape.”

-Holly Copeland, Spatial Scientist
The Nature Conservancy in Wyoming

Cool Green Science:

You’ve likely heard about declining sage-grouse populations in the West—and ongoing efforts to ensure the iconic bird doesn’t land on the Endangered Species List.

Sage-grouse get the spotlight, but mule deer share the same sagebrush-covered landscapes, especially in the winter when sagebrush is their primary food source.

Mule deer are also at risk as unprecedented levels of energy development, rural subdivisions, fences, structures and roads fragment the West’s once wide-open spaces. 

The Nature Conservancy has teamed up with the University of Wyoming, the Natural Resources Conservation Service, and the Wyoming Game and Fish Department on a new study to understand how sage-grouse and mule deer conservation efforts intersect in Wyoming. 

The groundbreaking study has now been published in the journal Ecosphere. Read the published study here.

“We want to show it’s not just about sage-grouse,” says Conservancy scientist and study co-author Holly Copeland. “It’s about building momentum and making sure all sagebrush species are part of the equation.” 

A GIS Exercise 

To complete the study, scientists use mapping tools called Geographic Information Systems (GIS) to create computer models of mule deer migration patterns in Wyoming. 

The resulting maps will allow land managers and conservationists to answer several key questions about where mule deer remain vulnerable to development impacts in Wyoming: 

  • Where do mule deer migration routes overlap or divert with Wyoming’s Sage-grouse Core Areas?
  • Where do mule deer migration corridors intersect with future risks from industrial and residential subdivision development?
  • How have conservation actions for sage-grouse benefited mule deer? 

These scientific models build on two previous Conservancy studies that show where energy development and wildlife habitat intersect, and how private-land conservation easements impact sage-grouse populations. 

Mule Deer on the Move 

Previously, says Copeland, biologists didn’t understand the timing of mule deer migrations. Now, through research by scientists Matt Kauffman and Hall Sawyer, they have a much better picture. Their findings suggest a “stop-over” pattern, where mule deer travel to an area and remain for several days before moving on.

Mule deer are likely following Wyoming’s greening-up in the spring, timing their movements to hit areas with new vegetation growth. 

In the winter months, mule deer converge on Wyoming’s lower elevation valleys, where they rely on sagebrush to survive

These basins are also where they encounter the greatest human impacts—energy development, roads, rural subdivisions and more. 

Studies suggest that mule deer are particularly sensitive to human activity, with one report showing an overall decline of over 40% in mule deer abundance on the Pinedale Mesa, an area of heavy oil and gas development.

As mule deer move to avoid certain areas, they risk crowding out others, effectively reducing the amount of habitat available. 

Putting Our Findings to Work 

Conservancy scientists hope the new study will give land managers and conservation organizations tools to make decisions that protect the most important mule deer routes. 

The new study will also reinforce the Sage Grouse Initiative, a Natural Resources Conservation Service program to halt sage-grouse declines in the West. 

"By finding out where mule deer are most vulnerable,” says Copeland, “we’re giving them a better chance to survive in an ever-changing landscape.” 

You can help! Support our science and make a difference for mule deer and other wildlife in Wyoming.

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