Wyoming Mule Deer Migration Project

To Migrate, Or Not To Migrate?

Each spring, mule deer from Wyoming’s Sublette Herd migrate up to 150 miles, one-way, from the Red Desert to the Hoback and Upper Green River Basins—the world’s longest mule deer migration. Anna Ortega, PhD candidate at the University of Wyoming, has spent the past five years studying three migration strategies used by these deer of the West.

Ortega has learned that not every member of the herd makes the long journey. Instead, the herd incorporates different migration strategies: long distance, medium distance and short distance. Some individuals don’t migrate at all. Migrations can be beneficial for many species, so why are some mule deer deciding to shorten their journeys or to not go at all? One of Ortega’s goals is to understand the costs and benefits of different strategies, as well as the potential benefit of a diverse migration strategy on herd-level performance

“The diversity of these migrations may be beneficial for the entire herd,” Ortega reported. “In some years, one strategy might perform poorly while another strategy does well. In the end, these strategies balance each other out and the herd can continue to thrive even in lean years.” Even though individual mule deer in this population may not migrate together, they do spend the winter together and breed together.

Before beginning her doctoral career, Ortega had worked on a variety of field projects ranging from plants and birds, to other mammals. While working as a wildlife technician she transitioned to the Kauffman Lab where she began her work with migration studies and fell in love with it. “It’s almost like the project found me,” Ortega said. “I didn’t understand I had that passion until I immersed myself in it.”

Ortega’s research will have applied benefits for conserving mule deer migration and improving the management of mule deer herds across the American West.

Ortega’s work is part of an ongoing migration assessment conducted by the Wyoming Migration Initiative. The research of the longest mule deer migration in the world is expected to continue after Ortega wraps up her doctoral work.

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