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5 Things Researchers Learn From GPS Collars

Here’s how hunter-funded GPS collaring affects big game management in the West
group of people tagging a dear with a collar.
Huggers are usually volunteers wanting a close encounter with wildlife. They have to maintain a full-body hold on animals whiles scientists attach trackable GPS collars. Kris Millgate/

Two types of people are on the mountain during wildlife round-ups. Runners and huggers. I’m a hugger, an intense hugger, and I must hug until a runner arrives. I’m helping the Idaho Department of Fish & Game capture big game animals. It’s my job to keep a mule deer doe wrapped tightly in my arms until a wildlife biologist, or runner, comes to collar it. Two feet of snow padded my fall when I jumped on the deer, but it’s also delaying the biologists. That’s why I’m hugging for all I’m worth. The doe is in fight mode. It screams in my face—similar to the vocal range of a goat—and I know a kick is coming. I tighten my grip, close my eyes and hide my face in fur.

It takes 10 minutes to put an $800 GPS collar on a deer. During that time, the animal is also weighed, measured, and tagged. Just ten minutes of touchy grabby then the kicker runs away wearing a new necklace. That necklace sends a pile of location points for years to come, which is the kind of information useful to biologists and, in turn, hunters alike.

A helicopter flying over a hillside covered in snow.
Drive netting involves a helicopter pilot flying at low elevation while funneling wildlife toward nets for capture. The operation is conducted with snow on the ground for extra padding during falls. Kris Millgate/

To learn more about how this kind of technology leads to your next buck, we spoke with Daryl Lutz, the wildlife management coordinator for the Wyoming Game and Fish Department, and Jon Rachael, Idaho Department of Fish and Game state game manager.

Idaho and Wyoming share a border, but wildlife doesn’t recognize borders so collared animals in one state can end up in a neighboring state, especially in the Greater Yellowstone Ecosystem (GYE). The GYE includes Yellowstone National Park and Grand Teton National Park plus portions of Idaho, Montana, and Wyoming. Animals collared for research in the GYE favor long migration routes. That’s one of the things we now know thanks to collars.

Here are five questions GPS collars answer for wildlife researchers.

Where The Animals are Going

The main motivator for collaring wildlife is tracking movement. Before GPS, researchers knew animals moved between points A and B, but exactly when and how was unknown. Now we know there are specific migration corridors for big game, especially in the West, that are lengthy and complicated.

Wyoming went for discovering migration routes in a big way. Researchers documented deer migration in 2013 by installing trail cameras along a route mapped by points relayed via GPS collars. It was groundbreaking scientifically and visually.

“[Tracking migration] ensures long-term sustainability in a herd that hunters are interested in,” Lutz says. “Preserving migration corridors and the ability to access important habitat ensures hunters continue to have the gift to pursue.”

How Many Animals are on the Landscape

Collars within a herd help wildlife researchers more accurately estimate how many animals are on the mountain. Like Wyoming, Idaho maps migration routes through data points sent from GPS collars. They also fly planes over winter range to count animals when they’re more likely to bunch up.

By pairing collar data with flight data, population estimates are more accurate. Population estimates determine harvest potential. That’s what hunters are interested in. Setting seasons based on more accurate information means the number of hunters on a hill won’t outpace harvest potential.

A collared and tagged deer.
Captured wildlife get three things in 10 minutes: a blindfold, an ear tag, and a GPS collar. Trackable collars help scientists set hunting seasons. Kris Millgate/

By knowing the numbers are low before the hunt starts, game managers can adjust the season or bag limit. It might change where and when you can hunt, but it doesn’t waste your time and money. This leads to less disappointment in the field.

“The thing that’s most valuable to us is monitoring the survival of animals we have collared. What percentage survives the year,” says Rachael. “We put collars out so we have a representation of what life is like for animals across a large area.”

To count the herd, you have to find the herd, and collars have always helped with that. In the 1980s, VHF (very high frequency) collars were used. They required someone on the ground, tracking signals with radio antennae. Those first VHF collars, along with aerial surveys, created the population models still used today. But it was more labor-intensive than GPS collars that send data via satellite to offices.

VHF collars served the same purpose black sheep serve for herders. For every 100 white sheep, there’s one black sheep. In a herd of 500 sheep, it’s faster to count the five black sheep than it is to count all 500 sheep. Additionally, if you know how the black sheep (collar) is doing, you have a pretty good idea of how the rest of the herd is doing. If half of the black sheep die, something is wrong with the whole herd, and it’s time to get on the ground and see what’s going on.

GPS collars track much more than population, but population was the original purpose and it continues to be an important harvest predictor as technology advances and models are refined.

A deer tagged with a deer collar.
GPS collars help researchers learn about how deer and other animals are utilizing their summer range. Wildlife GMBH/Alamy

How Migrating Animals are Using the Landscape

Layer GPS data points on top of a topography map and you’ll notice the points aren’t evenly spaced. That’s because animals don’t move at the same speed non-stop. A cluster of location points stacked on one another is common, and it indicates a stopover—or a place where animals eat and rest. Migrating big game rely on land stopovers just like migrating waterfowl rely on ponds. If you know the forage available at a particular stopover, you know what the animals are eating. You also know when they’re not eating.

When wildfire blackened nearly 75 percent of Idaho’s Tex Creek WMA in August of 2016, food for wild grazing went up in flames too. When snow fell four months later, Deer and elk migrating to Tex had nothing to eat when they reached their documented winter range. Researchers knew the animals would arrive. The collars told them that. But the animals didn’t know they would arrive on fruitless ground. The grasses and brush had burned. The stopover was gone.

To keep those wild animals from pushing into agricultural land, the Idaho Department of Fish & Game put out hay. This kept herds in one place and out of trouble. The department also enacted an emergency hunt because even with hay, some animals would starve. Harvest when healthy is preferred over letting the animals starve to death. Hay and emergency hunts haven’t happened at Tex since then, but knowing what was coming helped managers deal with the situation in real-time, rather than reacting a few years later when hunters had no harvest.

“We’ve had to take a bigger look based on tens of thousands of location points to really get a better grasp on how deer use the landscape,” Rachael says. “Knowing where deer are during hunting season versus where we count them on winter range is absolutely critical, but so is understanding where they are in summer.”

Following game animals on summer range matters because it determines how well they’ll hold up in winter. When natural food sources go up in summer smoke, as it’s prone to do during wildfire season, herds either shift their range or starve. Because so many animals are collared, from grouse to grizzlies, their stopovers along with what they eat is starting to create a grid of data across developed and undeveloped areas. When fire smothers an area, researchers already know which animals will be impacted based on an area’s specific collar history.

How Many Animals are Dying

Wyoming has about 2,300 animals collared right now. Idaho has nearly 2,000. The bulk of both totals include deer and elk and a few dozen bighorn, moose, pronghorn, lions, wolves, and bears too. When a collared animal doesn’t move for an extended period of time, the GPS signal changes (like an E.R. heart monitor switching from a continuous beep to a flat-line). When that happens, it means one of two things: The collar fell off or the animal is dead.

“During hard winters, you find them curled up and skinny,” says Rachael. “When we have high losses due to malnutrition, we know we’re having a rough winter without having to do a flight survey.”

deer wrapped in a blindfold.
Blindfolds, similar to the soft sleeve of a t-shirt, cover an animal’s eyes during live capture. It protects their eyes during the chaos and it also tends to calm them down. Kris Millgate/

Flight surveys typically operate in a three to five-year rotation. Before GPS collars, season setters had to wait for these surveys to adjust bag limits appropriately. If a bad winter killed enough animals to impact the limits, they wouldn’t know until too late.

“We would know [before GPS collars existed] winter kind of sucked and people reported finding winterkill, but we had no real count of impact until the next fall when [hunter success] would tank,” Rachael says. “Sometimes it was pretty sobering. We didn’t appreciate the severity of winter loss back in the 90s. We lost a good portion of populations and we did not respond.”

Now research from GPS collars allows for a quicker response. In the winter of 2016-17, Idaho was buried in snow. It stacked deep and stayed for a long time. Only 41 percent of collared mule deer fawns made it to March 31, 2017. It was a season of terrible returns suffered at the hands of Mother Nature, but the department knew it right away.

With more than half of the collared fawns dead by spring 2017, The Idaho Department of Fish & Game responded. For fall 2017, they reduced hunts in some areas and completely eliminated hunts in others. That’s how rapid response to winter conditions and real-time mortality data ultimately helps hunters.

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Non-residents and residents can find information on what hunting will be like in a particular region in the future by studying annual wildlife reports available to the public. Collar data, flight surveys, survival rates and harvest statistics go back to the 1970s in Idaho. Hunters can avoid applying for draw hunts in areas that have low concentrations of animals by looking at mortality data or eliminating areas that have experienced draught or bad winters years prior.

“It’s a whole new world of landscape use and how we as humans, whether we’re hunting or developing, affect wildlife,” says Lutz. “Our ability to balance how we use the landscape and make sure animals persist on the landscape is only getting better.”

How Many Animals are Being Born

While the location and mortality signals generated from GPS collars are helpful on adult animals, researchers are taking an even more in-depth approach with bighorn sheep lambs. Respiratory disease is suspected of causing the chronic decline of Wyoming’s bighorns in the last 30 years, and keeping a close watch on sheep maternity is important. To get ahead of the disease, researchers there are implanting transmitters in ewes. When the ewe delivers a lamb, it also delivers the transmitter which sends a signal to researchers.

A bighorn ram in the snow.
A collared female bighorn sheep in Yellowstone National Park. Chritine Ney/Alamy

“Now you ask, ‘Why do we need to know that?’” Lutz says. “Well, it gives us the opportunity to collar that lamb. We can get to the little bugger before we can’t catch it. There’s a team on location as fast as possible. They capture it by hand and employ a smaller collar on a lamb through the first several months of life to determine how it does. If it doesn’t survive, we get back on that collar ASAP because it sends a mortality signal.”

More than half of the lambs wearing collars in 2019 died of pneumonia. Wyoming knows that because crews traced mortality signals back to collared carcasses. Those carcasses went to the state lab for a necropsy. With the cause of death confirmed, researchers plan to expand sample size for two more years while also trying to better understand where the cause of death is coming from so they can take action. If more lambs survive, there will be more huntable adults.

“Most hunters are interested in conservation,” Lutz says. “They want to know as much as we do. They want to know why there aren’t as many sheep as there once was. And it’s their money that funds this work.”

A mule deer doe running away after recieving a GPS collar.
A mule deer doe running away after receiving a GPS collar. Kris Millgate/

Hunter dollars paid for the collar being secured around the neck of the deer I’m hugging. The GPS unit is already sending a signal so the deer’s first location point is also where I’m laying. In a quick two-step move, I open my arms and legs while rolling my torso and face away from the action. The deer explodes to its feet and sprints through the sagebrush. Its belly, still thick with summer forage, bounces between its front and back legs as it rushes away from the human huddle. That’s a good sign. It means this muley has enough fat reserves to make it through the rest of winter.

If you harvest a collared animal

You can legally harvest an animal wearing a collar during hunting season, but wildlife agencies ask that you turn that collar in. GPS units cost $800 to $2,000 each depending on how programmable they are. Plus, data is stored on collars and they can be reprogrammed for another round of fieldwork on a different animal.