Using GPS to Track the Health of an Ecosystem

Steam rises as yellow sunlight burns off the morning mist. Silence gives way to early morning bird calls. Out of the silhouette of trees into the lightening grass steps a dark shape, followed closely by a smaller shadow. A mother elk and her calf have come to graze the meadow. Any change of sound or shape will speed the mother’s head upright. She is wary, ready to move to safety if danger appears. Other animals begin to move toward the sunlight. The herd is stepping forward to eat, thrive, breed, and survive. As the herd moves, other eyes are watching them. But they are not being observed by the concentrated gaze of a predator, as might be expected. This herd of elk is being tracked by researchers using Global Positioning System (GPS) devices.

Through careful observation, researchers have come to understand the importance of elk migration patterns in Yellowstone National Park to the health of the surrounding ecosystem. The elk may serve as a tourist attraction, but their population reflects the condition of all living things in this area.

How Do the Habits of Elk Predict the Health of an Ecosystem?

In Yellowstone National Park, elk serve as food for eagles, wolves, and grizzly bears. But their purpose extends beyond that of prey. Researchers found that the habits of elk have a greater impact on the health of the environment than they previously realized.

Ecologist William Ripple, of Oregon State University, began studying wolves as their populations slowly returned to Yellowstone National Park. “Back in 1997, I became aware that the aspen trees in Yellowstone were declining,” Ripple explains. “There was disagreement and confusion as to why these trees were disappearing, so I set out with graduate students to unravel this mystery.”

What they discovered was that the browsing patterns of elk either helped or hurt plant life around the area. Places where the elk felt secure from the wolves were more heavily foraged, while those areas with a denser wolf population had taller tree growth. And where the trees grew taller, other animal populations, such as beavers, increased.

Years later, another study corroborated Ripple’s findings. Reno scientist Kelley Stewart and her team studied the effects of differing sizes of elk populations on their food and habitats at the Starkey Experimental Forest and Range in northeastern Oregon, University of Nevada.

The team created two populations of elk with different densities. One herd had a low density of about 10 elk/mile (24 elk in a 1500-acre study area), and another had a very high density of about 60 elk/mile (200 elk in a 2100-acre study area).

What they concluded was that areas that experienced low levels of foraging by elk showed greater plant growth than either those areas not foraged or those that were highly foraged by elk. Low populations of elk encouraged greater plant growth and diversity. High populations of elk had negative effects on the elk herd’s population itself as well as their territory.

Researchers determined that a well-managed elk population promotes biodiversity and ecosystem functioning. So if the elk populations of Yellowstone could be tracked, they would give ecologists a good idea of the condition of other animal and plant populations. The question became how to manage a migratory population that moves around and beyond park boundaries.

How GPS Tracking Helps Scientists Manage Yellowstone National Park

In Yellowstone National Park, the elk population serves as a gage of the health of the ecosystem. Whatever happens to them creates a ripple effect on the rest of the plant and animal life. By using GPS tracking devices, researchers can record reliable data from the elk’s migration habits.

In the past, researchers have been inclined to look at the elk individually while the animals were contained within the park’s borders during their winter or summer range. Arthur Middleton, a Yale ecologist who is also a research associate with the Wyoming Migration Initiative at the University of Wyoming, decided that he wanted to take a less fragmented approach. His desire is to try to get a larger picture of the herd’s migratory movements and how they might be impacted by climate change.

In March of 2014, he and his team began tracking the elk with GPS collars that signal the elk’s exact location every 45 minutes. The precision of these measurements will give researchers the necessary information to map the herd’s route by time and location. Middleton hopes to learn the elk population’s migration patterns and how to better oversee them in the future. He also hopes to learn whether changes in elk migratory habits will be reflected in the herd’s health and numbers.

In addition to using GPS to track the elk, cameras posted along the route will allow researchers and the public alike to see when and how the animals move as they migrate along their route. By educating others about the importance of herd migrations, Middleton desires to reinforce the importance of saving preserved lands to serve the needs of these animals. And he predicts that this information will eventually allow for remote monitoring that will conserve park resources.

The migration of the elk is critical to the balance of the ecosystem at Yellowstone National Park. Good management of the animal populations will serve the health of the park, and information gained may be used to improve management at other important wildlife territories.

Using GPS to Track the Health of an Ecosystem