Several hours into the Yellowstone backcountry, a group of researchers stops along a planned route. On their backs are packs filled with water, food and audio recording equipment. One of them slides the pack off, pulls out a small, hard-shell box and tests whether the recorder works. Then, another affixes the box to a cottonwood tree before the group packs up their belongings and moves on to the next stop. The installed devices they leave behind will capture the sounds and howls of a wolf pack, giving scientists more data to decipher how one of America’s most elusive apex predators communicates.
Elsewhere, equally remote, a veterinarian assesses the health of a young tranquilized wolf while a biologist secures a loose, but not too loose, satellite collar around the animal’s neck. Equipped with a battery-powered transmitter, that collar will allow researchers to follow the wolf and better understand its movement, predation and use of the landscape. Motion-triggered trail cameras, also strategically placed throughout these wild spaces, will offer another window into the lives of wolves, capturing moments that would otherwise go unseen.
Each tool offers a different piece of the same puzzle, helping scientists build a more complete picture of how wolves live and, ultimately, how humans can better coexist with them.
VHF and satellite tracking collars
Wildlife biologists have used radio collars for decades, with the first-ever radio collar for a large mammal attached to a grizzly bear in Yellowstone National Park in the late 1950s by renowned biologists and brothers Frank and John Craighead.
The collar, called a Very High Frequency (VHF) collar, is strapped onto a sedated animal using a leather adjustable strap, a battery box and a radio emitter. A radio telemetry receiver, a handheld device with a small antenna at the end, can track that signal. If the receiver is pointed in the general direction of an animal’s location, it picks up signals emitted from its collar. When the Craigheads first introduced VHF collars to large mammal research, they sparked a scientific revolution whose ripple effects would shape wildlife research and conservation for generations.
Taylor Rabe, a former biological science technician with Yellowstone National Park and current education director with Conservation Nation, regularly relied on VHF collars to track wolves in the frontcountry. From the roadside, she’d scan the landscape with a receiver and wait for a signal picked up from a distance.
“I think a big misconception about radio telemetry is that it does not tell distance,” Rabe explained. “The signal’s going to sound the same. It’s all line of sight, whether that animal is 100 yards off the road, in view or 12 miles away on top of a mountain. We still have to know behavior, travel routes, places that you would expect to see whatever animal you’re looking for to be able to find them.”
While VHF collars remain an important and cost-effective tool, technological advances have produced more precise, though more expensive, GPS satellite collars. These collars have enabled extensive data collection on animal movement and behavior, including mapping GPS clusters. These clusters occur when a collar reports several locations in a specific area – indicating that the animal uses that area for an extended period – and can help scientists predict predation sites, dens and territories.
VHF and GPS collars are widely used in wolf management efforts across the country and are particularly useful in densely forested areas or vast backcountry where spotting a wolf can be challenging.
Yet radio collaring has drawbacks. The process can be invasive, as it requires scientists to tranquilize the animal. Still, Rabe emphasizes its importance in collecting invaluable data. “Scientists are shifting to implement different methods that can provide some of the same information as our radio collaring, but I don’t think collaring will ever go away,” she said.
Some wolf collars have even been altered to carry cameras. In 2021, Voyageurs National Park staff tracked a wild wolf wearing a camera collar and captured first-of-its-kind footage of the predator’s movements, including fishing in a freshwater stream, gnawing on deer bones, resting in an obscure den and exploring its territory freely. The recordings offered a rare, uninterrupted and up-close view of a wolf’s life in the national park’s forests.
Motion-triggered trail cameras
While collars help scientists understand where wolves travel, trail cameras offer a closer look at their behavior.
Strategically placed trail cameras in areas with wolf activity capture moments scientists might otherwise miss. A 2022 study funded by the Idaho Department of Fish and Game used motion-triggered cameras to estimate wolf populations across three areas of the state, demonstrating their potential as a cost-effective monitoring tool. Beyond monitoring wolves, cameras can capture images of other wildlife and remain unattended for extended periods, allowing researchers to collect data on multiple species with a single device.
To ensure they have enough information, scientists program trail cameras to record video or capture photos in burst mode, generating thousands of images and ample footage. Relying on the human eye to manually sort and filter these images can be time-consuming and error-prone. Artificial intelligence is helping streamline this process, though further advances are needed to improve its accuracy.
Improvements to AI may not be too far away. In 2025, researchers at Oregon State University trained an AI agent to identify bighorn sheep more accurately by rigorously training it on different photos of that single species in the ecosystem over time. The project challenged a one-size-fits-all approach to AI and recommended training models to specialize in identifying specific species.
Autonomous recording units and bioacoustics
Beyond tracking movement and capturing behavior on camera, researchers are exploring another way to understand wolves: listening to them.
Bioacoustics research on wolf vocalizations could be groundbreaking for understanding the species. During her time at Yellowstone National Park, Rabe spent countless hours helping researchers deploy autonomous recording units (ARUs) throughout wolves’ territories for passive acoustic monitoring. She was among the first researchers to install ARUs in Yellowstone in 2022 for what is now called the Cry Wolf Project.
Dr. Jeffrey Reed and Dr. Dan Stahler of Yellowstone’s Wolf Project founded the Cry Wolf Project, the National Park Service’s long-term study of Yellowstone’s wolves. It aims to build the world’s largest database of wild wolf vocalizations by collecting and analyzing ARU data and recordings and leveraging artificial intelligence to identify patterns and develop unique profiles.
“Scientists are really focusing on wolf vocalizations and how they differ from one another. We are trying to understand what they are saying, when they are vocalizing, how often they are vocalizing and even how many of them there are. It’s kind of like being in a room full of a thousand people. If your mom or sister spoke, would you recognize her voice?” Rabe noted. She estimated that the technology is about 90% effective. Still, Yellowstone, famous for its open vistas and passionate wolf-watching community, has served as the ideal place to test the accuracy of an AI agent’s data.
“Yellowstone is perfect to test our theories in bioacoustics. There, we know exact pack compositions and the exact number of wolves in these packs. So we could take these ARUs, pull the spectrograms off of them, which are pictures of the wolf vocalizations, and put them into AI to then count the number of wolves,” she added. Those results can then be pressure-tested with real-time observations.
“Maybe we have an ARU in a rendezvous site where all the wolves are, and we get this epic chorus howl vocalization recorded. I’m tracking the wolves from the road with a spotting scope, seeing it happen in real time, and also recording it on my phone. We could pull the data, throw it into AI and see if this AI model can tell me how many wolves were howling. It could tell me 16 wolves were howling, but in real time, I know I only saw 10. This testing allows us to tweak the programming and figure out what we need to make it more accurate.”
ARUs have also shed light on how humans affect wolf behavior. Recordings have captured human activity, alerting scientists to hikers who may be too close to den areas or rendezvous sites.
Advances in bioacoustics could help researchers better understand wolf populations and pack dynamics in remote landscapes, providing valuable insights to inform conservation, public education and conflict mitigation efforts.