Scientists Reveal One Mule Deer Has Migrated Further Than Any Other on Record

by Caitlin Berard
(Photo by James F. via Getty Images)

When you think of migration, masses of birds flying south for the winter are likely what comes to mind. Totally fair. The majority of migratory animals are, in fact, birds! However, they’re far from the only creatures to seek out warmer climates when the weather turns cold. Bats, seals, whales, reindeer, butterflies, and bison also seek refuge from the brutal winter months by migrating to warmer locations.

One rather surprising migratory species is the mule deer. Unlike their relatives, the whitetail deer, who are homebodies and prefer to hunker down for the winter, mule deer will travel upwards of 100 miles in search of warmer weather.

Scientists have tracked the migration of mule deer for years, attempting to understand more about their seasonal movements using collars equipped with GPS technology. Back in 2016, they collared a muley doe, dubbed Deer 255, and what they found shocked even the most knowledgable deer experts.

Like all mule deer, Deer 255 migrated in summer and winter, seeking higher, cooler elevations in summer and lower, warmer regions in winter. Unlike the other collared deer, however, Deer 255 traveled exceptionally far with the change of the seasons.

“What makes this deer really special is that her bi-annual migrations from, the start to end point, is over 242 miles,” Gregory Nickerson, a Wyoming Migration Initiative rep, told Field & Stream. “Of all the deer we’ve collared, she’s the one that’s had the longest yearly migration.”

“When we started tracking her in 2016, she went up 160 miles from Red Desert to the Hoback Basin, which a large herd does,” Nickerson continued. “That in and of itself is a long migration. But then she continued on further for almost 100 more miles up into Idaho.”

Researchers Fascinated by Mule Deer’s Extreme Migration Route

Scientists remain baffled by the mule deer’s extreme migration route. By studying her movements and that of deer like her, they hope to learn more about why certain mule deer travel farther than others.

They know that most deer migrate the route learned from their mothers, and Deer 255’s mother must have been uncommonly sharp. Rather than harming the doe, her ultra-long migration route appears to be beneficial to her health and that of her fawns.

“It’s really hard to say why she does it,” Nickerson explained. “Mule deer migration is driven by memory. This migration must’ve been a successful strategy in the past, and so she’s continuing it.”

“There are good habitats that she could’ve stopped at earlier,” he continued. “But by making the super long spring migration, she’s extending the amount of time she can gorge on freshly sprouted plants. She’s a very big deer compared to the average.”

Now that they have the unusual yet successful example of Deer 255, researchers hope to find more deer with unique migratory strategies.

“She’s a unique individual,” Nickerson said. “Migration for mule deer really drives their summer weight gain, reproductive success, and overall abundance. She’s showing us the costs and benefits of this ultra-long migration strategy.”

“As research continues, I’d love to find a deer that travels even further than Deer 255,” he added. “More research will yield even more fascinating examples of deer migration.”