How Hunters Can Understand Migration Routes Better

Brian Wakeling has a hot tip for hunters looking to leverage a growing body of knowledge about how, when, and where big-game animals move across Western landscapes: Pay attention as you drive. Wakeling, wildlife management bureau chief for Montana’s Department of Fish, Wildlife & Parks, says those yellow signs depicting a jumping deer aren’t arbitrarily placed on highway shoulders. Instead, they’re literal signs signaling a hot spot for wildlife crossing, placed there either because of a demonstrated history of vehicle collisions with elk, deer, pronghorns, and even bighorn sheep or because GPS collars indicate that big-game animals routinely cross there.

For hunters, they’re signs that wildlife abundance is higher in that particular spot than in adjacent areas. “We have thousands of [GPS] collared animals on the landscape, and what we’ve learned from them is invaluable,” says Wakeling. “Internally, we use that data to understand migration patterns, but also to recognize impediments to movement across the landscape, whether a fence or a highway.” But individual waypoints from Montana’s collared critters aren’t publicly available.

What can be viewed, on department websites or shared with department partners, are aggregations of data that have been edited to remove hyper-seasonal use of specific topography. Just as wildlife departments generally don’t share with the public the real-time waypoints of individual collared animals, they are also careful not to “hot spot” wildlife movement.

“We’re cognizant of the sensitivity of our data, which can identify where and when individual animals are moving through very specific places,” says Wakeling. “You could understand the value [of that data] to outfitters or to real estate developers or to hunters doing remote scouting, but we have a policy that keeps the publicly available scale at a level that doesn’t highlight specific animals or properties, but at a level that reveals important trends that can help us with management decisions.” Instead of mining waypoints, Wakeling suggests hunters pay attention to those road signs.

“Our history certainly indicates that roadkill data corresponds very closely with GPS telemetry data,” he says. The tension between the collection of migration data and its availability to the public is growing as hunters demand more granular information as they plan what could be once-in-a-lifetime hunts. The digital platform GoHunt, for instance, includes a “migration layer” that color-codes elevations with seasonal use by big-game animals. The digital mapping app onX includes a Colorado-specific layer that shows the summer and winter ranges of nine big-game species in the Centennial State, along with their migration routes. Utah Division of Natural Resources, which has some of the most robust migration data of any state, routinely updates a webpage that shows migration routes and the movements of specific animals.

BUILDING A COMPOSITE PICTURE

Simply recognizing the connectivity of habitats is one portion of the knowledge hunters need to acquire as they plan hunts. But that’s at best a quarter of the whole picture. The second quarter is seasonal use. Migration is triggered by changes in weather that don’t always arrive at the same places at the same time. The variation depends on latitude, elevation—both unchangeable— combined with the highly erratic weather conditions. The third quarter is species-dependent, and here’s where GPS data can be highly useful.

Mountain mule deer tend to tolerate more snow than elk, which become physically depleted from the rut, which causes an earlier migration to lower, snow-free elevations. So, if you’re expecting to use elk migration data to inform your mule deer plans, you may be disappointed.

The last portion of knowledge to plug into your personal planner is how your target species responds to adversity, expressed either as an impassable highway or fence, or hunting pressure that they encounter on the interface of a land-use change. Here’s where GPS data, even at the rough scale that most states present it, can be extremely useful.

Look at specific, abrupt changes in migration routes. That’s an indication of an impediment, whether physical (a woven-wire sheep fence or a highway) or social, maybe a spot where they’re vulnerable to hunters, or a rural subdivision with so much human activity that wildlife veers around it. Even the presence of a barking dog can cause wildlife to adjust their migrations for as long as 10 years, or as long as that irritating dog is expressing its frustration to the world. Smart hunters will build a composite picture, using each of these layers of knowledge, to be at the right place, at the right time, to intercept the right animal. The rest of the challenge, stalking into range and placing a killing shot, is entirely up to the hunter, and for most of us that’s the fat half of the equation.

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USEFUL TOOLS TO MIGRATION DATA

“There’s no shortage of publicly available data that illustrates what’s become the most dynamic part of space-age wildlife management: tracking GPS-collared animals. Most Western states share maps that show how big-game species move across their landscapes, thanks to the satellite-delivered waypoints that can be downloaded every week, every day, or even every hour, depending on the needs of the agency that collared the animal.

The mother lode of migration data is contained in the master document, Ungulate Migrations of the Western United States, Volume 1, published by the U.S. Geological Service that synthesizes work done across the region: pubs.er.usgs.gov</p

The Wyoming Migration Initiative, the first and still the best synthesis of Cowboy State migration efforts, has more maps and information than you have time: migrationinitiative.org

In Montana, digital scouters might consult a website (mdt.mt.gov) that funnels GPS data from collared animals, along with wildlife collision data, into a site that informs where transportation managers might build wildlife-excluding fences or wildlife-friendly overpasses.

Colorado’s Parks and Wildlife Department has a similar aggregation of migration data: cpw.state.co.us

Utah has more collared animals—more than 11,000—and more waypoints (41 million) than any other Western state. The Division of Wildlife Resources aggregates all this information in a series of fascinating maps available on a DWR website: wildlifemigration.utah.gov

Idaho’s migration data is available from a number of digital sources, but a fascinating window into the world of mule deer in the Boise River drainage shows how elevation, terrain, and seasonality all combine to put bucks on the winter range: hub.arcgis.com

Lastly, if you want to get at the primary document that fueled most of this big-game migration energy, visit the Department of Interior’s guide to implementing Secretarial Order 3362 that authorized research into migration corridors: wafwa.org/so3362/