As Idaho’s population grows, land managers, recreation groups and scientists are working to solve a delicate problem. They’re balancing the need to preserve the federally protected golden eagle population that nests on public lands and are sensitive to human encroachment with maintaining networks of hiking, biking and riding trails that are becoming more popular with every passing season.
“The trend in Idaho, the U.S. and the world in general is that recreation on public lands is rapidly increasing,” explained Dr. Kathryn Demps, an assistant professor of anthropology at Boise State.
Raptor biologists noticed that golden eagles in the Owyhee Front south of Boise were abandoning nests in close proximity to trail networks and areas with high off-highway vehicle (OHV) use.
“Wildlife doesn’t ignore human activity; it responds to it,” said Dr. Julie Heath, an associate professor of biology. “In the case of these raptors, it appears they are responding by abandoning nests.”
According to the Bald and Golden Eagle Protection Act, it’s illegal to engage in any behavior or action that disrupts the raptors’ nesting and reproduction cycles. As stewards of the land, this means the Bureau of Land Management (BLM) is responsible for identifying and mitigating activities that affect eagles. But accomplishing that task isn’t as simple as alerting the public to the alarming fact that human presence might compromise eagle populations.
“Research in the last several years indicates that education isn’t sufficient to create eco-friendly behavior,” Demps said. “There are not a lot of restrictions on public lands and even if you tell people that they’re harming golden eagles, that’s not enough to remove conflicts with wildlife. Instead, we need to identify management strategies that will allow for recreation and protect eagles.”
One possible solution the BLM explored was closing trails near golden eagle habitats. However, land managers are keenly aware that they also have a responsibility to provide recreation opportunities to the public.
“Closing trails has a lot of local political ramifications,” explains summer 2015 graduate Rob Spaul. Spaul studied the influences of recreation on golden eagles for his master’s thesis and continues to work on the project as a Boise State research assistant in partnership with the U.S. Fish and Wildlife Service. “Land managers didn’t want to go full bore without sound science to back it up.”
In 2011, Heath received a three-year $58,000 grant from the BLM to study the effects of trail closures on golden eagle populations. Heath assembled an interdisciplinary team of biologists, anthropologists and geoscientists to also study human behavior, and why and how recreationists utilize the landscape. In addition to Demps and Spaul, now a research assistant at Boise State, biology graduate student Eric Frey joined the team to specifically study how people use OHVs on trails.
Golden eagles are native to many areas in the Northwest. That’s not to say they’re common – there are only about 80 breeding pairs in the Owyhee Front, which is where the Boise State team focused its research.
The raptors are similar in size to bald eagles – male wingspans can reach up to seven feet and females eight feet – with large bodies and long, broad wings tipped with distinct finger-like feathers. Their name derives from the golden-brown helmet of feathers covering their heads and necks.
The raptors aren’t migratory. They live in territories year round, rotating between several nests in their area over the years. That means there isn’t a time of year when they aren’t susceptible to human disturbance. Within their territory, golden eagles prefer to nest in open terrain, like rocky plateaus, outcrops or ledges cut from cliff faces, and other habitats where upwind drafts help them take off and soar. In other words, the same beautiful viewpoints that attract recreationists.
“Those landscape features are valued by people, but not because eagles are there,” Heath explained. “That may create a point of conflict that’s not deliberate on the parts of people or eagles, obviously, but our team was interested in understanding what drives human behavior on the landscape and what ways we can influence it and the decisions people make.”
Compounding the problem, golden eagles have a relatively long breeding season. After a February courtship, golden eagles lay between one and four eggs in late February or March. It then takes the eggs 45 days to hatch and another two months for the offspring to become fledglings that are ready to leave the nest.
“You’ve got about 130 days to manage for where eagles are susceptible to disturbance. That’s a long time to account for when you’re talking about trail closures,” Spaul explained.
In January 2013, team members began their field research, which included intense four-hour behavioral monitoring of 23 eagle territories. The team also set up trail cameras in territories for 45-day periods during breeding season and even monitored closed trails, noting that some people complied with trail closure signs while others did not.
“We sat and watched how close to the nests people got, how close they got to the eagles and the eagles’ responses,” explained Spaul. “Did the eagles watch from their nests or flush?”
From the data collected and interpreted, the team reached these conclusions:
- The number of pedestrians, horse riders and mountain bike riders in the breeding pre-season (January-February) had a negative influence if the eagles laid eggs.
- The seasonal average OHV use negatively influenced the likelihood that eagle territories would be occupied.
- Acute peaks in OHV use negatively impacted nest survival.
- Ninety-six percent of pedestrians on the landscape were delivered there by motorized vehicles (trucks, SUVs and OHVs).
- The volume of pedestrians on the landscape reduced nest attendance. The less time eagles spent on their nests, the less likely their young would survive.
Using temporal and spatial data collected from the OHVs, and their observations, the team built a simulation model to predict how golden eagles might respond to sustained levels of recreation, versus increased recreation or even decreased recreation, over a 50-year span.
“Our simulations showed that if we kept recreation the same as it is now, there wouldn’t necessarily be a decline in eagle populations,” Heath explained. “For the most part, eagle populations would be stable. But the smallest increase – 1 percent a year – leads populations to decline by half in the study areas.”
People often ask Heath and other biologists if wildlife couldn’t simply get used to humans.
“There’s a lot of variation among species on what will get used to humans and what won’t,” she explained. “Eagles are long-lived animals with few offspring. It would take a long time with many generational changes for eagles to get used to humans.” Simulations have shown that becoming desensitized to human disturbance wouldn’t happen fast enough to keep eagle populations steady.
“This all underlines the need for BLM to manage recreation,” Heath said. “Based on what we have learned from eagles and people, there are several options that will allow both to coexist.”
The group’s next step is using Frey’s OHV user data to interpret how people use the trail systems, what they want in an outdoor experience and how that relates to eagle habitats.
“We need to improve the level of understanding people have about their influences on wildlife,” Spaul said. “There’s a persistent misconception that non-motorized users don’t have as much of an impact on the landscape. We all have an impact and we need to manage our use so our grandchildren can hike, ride and bike and not just see a devastated landscape.”
Spaul points out that we already have a robust model for recreational management in the form of rafting and even hunting permits, which control how many people can enjoy a resource during peak seasons. The same type of model could be adopted on trails to help give people more of a “wild” experience, while simultaneously protecting wildlife.
The team’s research is far from done. Raptors are top predators; as such, they’re good indicators of ripples in the environment and among prey species. Heath and Demps, in collaboration with Dr. Neil Carter, an associate professor with the College of Innovation and Design who studies human-environment systems, are writing a proposal to study how human activities affect prey species in Idaho and Indiana, in conjunction with researchers from Purdue University.
“There’s some evidence to show that in areas with a lot of people, wildlife become more wary, and that actually makes it harder for predators to capture prey,” Heath explained.
“We still don’t know how recreation influences prey or habitat degradation,” Spaul said. “No one’s studied it yet. The case is not closed.”
“Only by having these different types of scientists work together can we solve these complex environmental changes that are happening so rapidly,” Heath added. “We have our students work across disciplines so the next generation of scientists can be well equipped to address the complex environmental problems that we’re beginning to face today.”
In a related study, Julie Heath studies the impacts of road noise on nesting kestrels. Learn more in the video below.
Hometown: Williamsport, Pennsylvania
Degree Program: Master of Science in Biology
Advisor: Dr. Kathryn Demps
Research: “Factors affecting special and temporal distributions of OHV recreationists in a complex open trail system”
Eric Frey studies how people’s use of natural landscapes may impact wildlife — particularly federally protected golden eagles. The Owyhee Front Management Area, about an hour southwest of Boise, boasts more than 800 miles of trails open to off highway vehicles (OHVs). Frey spent this past spring at busy trailheads, counting recreationists and attaching GPS systems to their OHVs, which catalogued vehicle locations every five seconds.
Frey is analyzing how riders use the complex trail system and what might influence differences in riding behaviors, including where people stop and for how long.
“Ideally, we’ll better understand the behaviors of OHV riders and what drives trail use patterns, giving land managers a more complete picture of how to provide great recreation opportunities while still maintaining healthy habitats for wildlife.”