During a 2021 Colorado Backcountry Hunters & Anglers (BHA) Rendezvous in southwest Colorado’s San Juan Mountains, we were joined by the local Colorado Parks and Wildlife (CPW) District Wildlife Manager. One of the topics we discussed was the increasing impact of off-road recreation on public lands habitat. 

As detailed in a 2018 Colorado BHA report (“Impacts of Off-Road Recreation on Public Lands Habitat”), “Wildlife habitat in Colorado is being significantly impacted by the proliferation of mechanized (i.e., mountain bike) and motorized (ATV/OHV) trails on public lands. Sportsmen and wildlife managers are finding that elk hunting opportunities, in particular, are being compromised by trail development in many parts of the state.”1  

Perry Will, a former CPW supervisor (now serving in the state legislature) said it’s not just more people living in what was once prime elk habitat, it’s more people venturing deeper into the backcountry all year long. Elk just don’t have the solitude they need any longer. “This is a major concern for us, with no easy solutions,” Will told CBS4 (in a 2018 interview).2  

For example, in a single decade, half of Eagle County’s elk population vanished. From Vail Pass to Glenwood Canyon—since 2007’s count by CPW, who use helicopters to check herd sizes in the winter—the numbers were down 50 percent. CPW previously issued about 2,000 hunting tags for the area. During 2018, 200 were issued. “It’s not like the elk are moving somewhere else, they are just dying off,” Will said.3  

Habitat Compression 

Publications based on data collected at the USDA Forest Service’s Starkey Experimental Forest and Range near La Grande, Oregon, from 2002 through 2004 show how motorized and non-motorized types of recreation––ATV use, mountain biking, horseback riding and hiking––affect elk.4  

Mike Wisdom is a research wildlife biologist with the Forest Service’s Pacific Northwest Research Station who worked on the project. His findings provide quantitative evidence about the effects of recreation on elk. In short: hunted elk populations generally don’t care to be around people, especially people on ATVs and mountain bikes, even during non-hunting seasons.5  

Elk avoid not only recreationists but also the trails associated with their activities. Their intolerance (as indicated by the distances they maintained) was highest for ATV riding, followed by mountain biking. To a lesser degree, the elk also avoided hikers and horseback riders. Some people participating in the study reported that they could see elk from the trails. However, telemetry data revealed that the elk that were seen represented a small portion of the larger population: most of the elk had retreated far enough to be hidden from view.6  

“When researchers in … Utah surveyed 640 hikers, mountain-bikers and horseback riders … they learned most recreationists thought they could approach wildlife far closer than what the flight distances showed,” explained American Hunter contributor Patrick Durkin. “In fact, half of the recreationists thought they had no impact on wildlife. Given such widespread lack of awareness of wildlife’s senses of smell, vision and hearing, silent-sports enthusiasts likely cause more harm than they’ll ever know.”7  

As people travel along a trail, wildlife tend to alter their behavior, avoiding or outright abandoning the area. Each time a human passes by, animals’ stress levels can increase and they are less likely to spend time eating, caring for young or sheltering. For many species, survival is strictly a mathematical equation.8 

Individuals feed as much as they can during the summer and fall, building up caloric reserves. During the winter, they are slowly starving. Human caused disturbance can lead to less time eating in the summer or fleeing in the winter (and possibly abandoning food) and unnecessarily burning calories.9 

 Hence, avoiding bikes and motors, in particular, takes a toll on elk (in two ways): increased energy expenditures and decreased access to food sources. Moving more than necessary and not having enough to eat can be detrimental to the viability of elk populations. For example, if females don’t put on enough body fat, they may not be able to reproduce.10 

Nearly half (44 percent) of all elk locations detected by telemetry during the recreation activities occurred in the 15 percent of the study area that was farthest from trails. In other words, a large number of elk sought refuge by crowding into a smaller range. “You’ve basically reduced what we call carrying capacity, the number of animals that can make a living on the landscape,” Wisdom said. He calls this type of habitat loss “habitat compression.”11 

A Biological Desert 

Jon Holst, a former CPW employee, is currently Colorado Field Representative for the Theodore Roosevelt Conservation Partnership. “According to Colorado Parks and Wildlife, there are nearly 40,000 miles of mapped motorized and non-motorized trails in Colorado,” he explained. “Some estimates suggest there exists an additional 25 to 30 percent of unmapped, user-created trails near popular mountain biking communities.”12 

And given that a whopping 85 percent of Colorado’s public lands are already open to biking, there are plenty of opportunities available without building new trails.13 In addition, most motorized routes are open to bikers. In fact, today some 98 percent of the lower 48 states is within one mile of a motorized route.14  

Ninety-two percent of all national forest lands in Colorado lie within one mile of a road and there are over 17,000 miles of roads in Colorado’s national forests.15 In the White River National Forest alone there are some 5,000 miles of system roads and trails.16 In the San Juan National Forest, where I hunt elk every fall, motorized road miles increased from 2,817 in the late 1990’s to more than 6,400 miles in 2008. How many miles are enough? 

“Researchers have clearly demonstrated the impacts that … trails have on wildlife—especially big game populations—because human activity drives wildlife away from preferred habitats,” Holst added. “For example, dramatic increases in trail development and use in elk summer habitat near Vail corresponded to a nearly 50 percent decline in the elk population between 2001 and 2015.”17 

Research comparing the effect of hikers, horse riders and “thrillcraft” (mountain bikes and ATVs/OHVs) on elk flight demonstrates significant differences in impact to wildlife. Hikers can clear a swath of disturbed animals 1/2-mile wide, especially if they have a dog. Equestrians may impact a swath 3/4th-to-1 mile wide, and ATV’s and mountain bikes clear a swath a full 2 miles wide!18 

Many mountain valleys are not more than two miles wide, so essentially if there is significant motorized or mountain biking activity it can preclude wildlife usage of that area. Furthermore, the flight response of elk is 15 percent faster from mountain bikes in comparison to hikers and equestrians.19  

A Colorado State University (CSU) study performed in the Vail area observed that the elk calf-to-cow ratio plummeted by nearly 40 percent as a result of simulated recreation use in elk calving areas. Reproduction levels during the treatment period were determined insufficient to maintain a stable elk population. With just over 8 disturbances per cow elk resulting in nearly 40 percent fewer surviving calves, each disturbance averaged nearly 5 percent probability of the death of a calf.20  

“… studies have established that big game, especially elk, are displaced by over a half mile from high use trails, and that the elk calf survival rate drops to zero when elk are repeatedly disturbed during critical times of the year,” Holst said.21 Another study of human disturbance of elk calving grounds found that with an average of 10 disturbances/cow above ambient levels, the elk herd showed no growth.22 

It’s also worth pointing out that hunting brings in over a billion dollars a year annually to Colorado, rivaling the income generated by the ski industry. We are eroding that business and income as we progressively eliminate lands where big game can birth and rear their young safely.23 

Biologists used to count over 1,000 head of elk from the air near Vail, Colorado, but when researchers flew the same area in February 2019 for an annual elk count, they saw only 53. According to CPW District Wildlife Manager Devin Duval, if trail building and closure violations in critical habitat continue, “It will be a biological desert.”24  

The Future of Elk Hunting 

In an article titled “The Future of Elk Hunting” (Traditional Bowhunter: December/January 2013), Durango resident David Petersen—a former U.S. Marine Corps helicopter pilot and Colorado BHA founder—wrote, “The three-part formula for assuring a rich elk hunting future … could hardly be simpler … Those three essential elements are: habitat, habitat, and habitat.”25   

Unfortunately, some mountain bikers in the Durango area (and elsewhere) are building illegal trails, and it’s causing an issue for land managers, wildlife officials and trail advocates that can’t rein in the longstanding problem. “We’re not talking small connector trails,” said Shannon Borders, spokeswoman for the Bureau of Land Management. “We’re talking miles of illegally built trails. And it’s not like there’s not a ton of recreational opportunities around town.”26 

CPW District Wildlife Managers, BLM and Forest Service public land managers, hunters and others are increasingly concerned about the impacts of off-road recreation on elk herds. “I had to leave one area due to ATVs. Then the great new area I found was recently designated semi-roadless instead of roadless, meaning mountain biking was allowed. The elk left,” said Durango area hunter Bryan Peterson. “I hunted an area for years that always held elk. When they expanded the trails the elk vanished,” added Johnny Rothones.27   

In addition, closing or decommissioning roads has been found to increase elk survival and the number of bulls, extend the age structure, increase hunter success and allow elk to remain in preferred habitat longer.28 Wilderness designation—the gold standard for wildlife habitat and backcountry hunting grounds—protects mostly high-elevation mountaintops in Colorado. A mere 3 percent of the lower 48 is protected as wilderness.  

Which is why Colorado BHA supports bills like HR 803 (Protecting America’s Wilderness and Public Lands Act).29 The legislation is a collection of nine separate public lands bills the House approved last year–including Rep Diana DeGette’s Colorado Wilderness Act and Rep. Joe Neguse’s Colorado Outdoor Recreation and Economy (CORE) Act.30 Conservation Colorado’s 2021 Conservation in the West survey found that 81 percent of Coloradans support a national goal of protecting 30 percent of America’s lands and oceans by 2030.31 

Backcountry Hunters & Anglers President and CEO Land Tawney praised efforts to conserve a minimum of 30 percent of U.S. lands and waters by 2030. “…we commend the Biden administration for taking a bold step forward toward their long-term conservation,” Tawney said. “We share a commitment to securing important landscapes, maintaining biodiversity and advancing durable policy solutions to mitigate the impacts of climate change.”32  

Dead And Gone 
It’s well documented that the combined hammer blows of expanding mechanized and motorized trails (and related recreation) on public lands is resulting in ongoing big game (and other) habitat degradation and compression that’s contributing to the decline—and expiration, in some places—of elk and other big game herds. 

Big game winter ranges in the valleys and foothills are already being lost to development, and new trails are extending this habitat loss. In theory, seasonal use restrictions can mitigate some disturbance-related impacts, but in practice there is very poor compliance and public lands agencies don’t have the resources to enforce closures.  

 During the 2017 Colorado BHA Rendezvous at Sylvan Lake near Eagle, Colorado, CPW District Wildlife Manager Craig Wescoatt stopped by. He’s concerned that elk are being displaced by mountain bike trails in the Eagle area.33 We are too. Many hunters are also mountain bikers, but we’re satisfied with being able to ride on the 85 percent of Colorado’s public lands, and thousands of miles of trails, already open to us.  

With so much of Colorado’s public lands base crisscrossed with trails and roads, “access” has become “excess” and the end result for hunters, big game and other wildlife is decidedly negative, with elk feeling the heat first and foremost. It’s a slippery slope from more mechanized and motorized trails to fewer elk and hunting opportunities, but here in Colorado we’re already getting a disturbing preview of how it ends.34 

“I don’t think people realize the dramatic amount the elk population has decreased,” said Craig Wescoatt. “The numbers we have counted have dropped some 50 (percent) to 60 percent in the last 10 years. We are not seeing the animals migrate to another area or permanently move somewhere else. They are just dead and gone.”35 

Additional/related information: 

• “Colorado BHA Report: Impacts of Off-Road Recreation on Public Lands Habitat.” Backcountry Hunters & Anglers: 5/21/18.  
• Sylvia Kantor. “Seeking Ground Less Traveled: Elk Responses to Recreation.” Science Findings #219 (U.S. Department of Agriculture-Forest Service Pacific Northwest Research Station): September 2019. https://www.fs.fed.us/pnw/sciencef/scifi219.pdf  
• Colorado Parks and Wildlife (CPW). “Emblems of the West: Colorado Parks and Wildlife researchers have set out to evaluate how human recreation may be influencing Colorado’s elk populations.” Colorado Outdoors: 3/22/21. 
• A set of related studies compiled by Keep Routt Wild.  
• Colorado Parks and Wildlife. “Colorado’s 2021 Guide for Planning Trails with Wildlife in Mind.” Appendix A includes standard protocols for how and where the trails are developed (i.e., Avoid, Minimize, Mitigate). 
• “Opportunities to Improve Sensitive Habitat and Movement Route Connectivity for Colorado’s Big Game Species.” Colorado Department of Natural Resources: 9/7/21.  
• Colorado Parks and Wildlife (CPW). “2020 Status Report: Big Game Winter Range and Migration Corridors.” CPW: May 2020.  
• Jon Holst, Colorado Field Representative for the Theodore Roosevelt Conservation Partnership. “Proposed management plan prioritizes wildlife.” Grand Junction (Colo.) Daily Sentinel: 11/7/21. 
• Jeremy Dertien, Courtney Larson and Sarah Reed. “Don’t hike so close to me: How the presence of humans can disturb wildlife up to half a mile away.” The Conversation: 7/14/21. 
• Christine Peterson. “Resort Town Blues.” Backcountry Journal: Winter 2021, p. 44. 
• Ryan Stuart. “Study: Mountain Bikes Disturb Wildlife More Than Previously Thought.” Men’s Journal: December 2020. 
• Jim Mimiaga. “Local elk herds decline; Colorado Parks and Wildlife seeks solution.” The Journal: 2/5/20. 
• Scott Condon. “Elk herd population plummets in Aspen, Vail areas as human use grows.” The Aspen Times: 2/1/20.  
• Christine Peterson. “Hiking trails are a path to destruction for Colorado elk: Recreationalists in Vail are having a devastating impact on the local herd.” High Country News: 8/27/19. 
• Christine Peterson. “Americans' love of hiking has driven elk to the brink, scientists say.” The Guardian: 8/25/19.  
• Patrick Durkin. “Silent Fight: ‘Non-Consumptive Users’ Disturb Wildlife.” American Hunter: July 2019. 
• Judith Kohler. “Elk vs. trails: Proposal in Steamboat Springs highlights conflicts over public lands (Mountain bikers want to ride in Routt National Forest, but others are concerned about the impacts on wildlife).” The Denver Post: 2/24/19.  
• Jonathan Romeo. “Where have all the elk gone? In Southwest Colorado, herds show distressing signs.” The Durango Herald: 11/15/18.   
• Matt Kroschel. “‘They’re Just Dying Off’: Elk Herds Disappearing In Eagle Valley.” CBS4-Denver: 6/22/18. 
• Pam Boyd. “Where has all the wildlife gone: CPW officials cite 50 percent drop in Eagle Valley’s elk population.” Vail Daily: 6/16/18. 
• Jonathan Romeo. “Illegal trail building a vexing problem for public land managers: Mountain bike paths built in recent years.” The Durango Herald: 3/20/18.  
• Editorial. “Do we truly value wildlife? Then it’s time to acknowledge that it’s up to everyone to help.” Vail Daily: 2/27/18.  
• Christine Peterson. “Conservation Groups Urge Biden to Boost Existing Programs for 30 by 30 Initiative.” Outdoor Life: 10/19/21.  
• “The 10th Mountain Division & HR 803 (Protecting America’s Wilderness and Public Lands Act).” Backcountry Hunters & Anglers: 9/27/21. 
• “Preserve Camp Hale and other public lands for future generations: Wilderness bill will protect Colorado’s robust outdoor recreation economy.” Colorado Newsline: 9/24/21. 
• Also see: https://www.huntfish3030.com/ 

Founded by Mike Beagle, a former U.S. Army field artillery officer, and formed around an Oregon campfire, in 2004, Backcountry Hunters & Anglers is the voice for our nation’s wild public lands, waters and wildlife. With over 40,000 members spread out across all 50 states and 13 Canadian provinces and territories—including chapters in 48 states, two Canadian provinces and one territory, and Washington, D.C.—BHA brings an authentic, informed, boots-on-the-ground voice to the conservation of public lands. Since the Colorado BHA chapter was founded by David Petersen (a former U.S. Marine Corps helicopter pilot) in 2005 (the first official BHA chapter), they’ve grown their boots-on-the-ground presence to some 2,000 dedicated hunters and anglers.