Anderson, mammals research leader with Colorado Parks and Wildlife, has come to this spot in western Colorado’s Piceance (pronounced PEE-awnts) Basin for nine years to radio-collar does and check their health before winter sets in. Since the 1980s, Anderson says the Basin’s mule deer population has dropped by 40-50 percent. “Mule deer throughout the West have experienced decline during the same times as here,” says Anderson, “and that’s left a lot of people puzzled.”
What’s happening here echoes what is happening in many other Western states, where oil and gas extraction and housing development have put more and more pressure on wildlife populations. State wildlife departments in Utah, Idaho, Wyoming and other states have been trying to boost declining mule deer numbers for decades. In Colorado, the latest proposal has already created controversy: killing cougars and bears in the Piceance Basin and the Upper Arkansas River in hopes of increasing deer numbers. Critics argue that the primary cause of the deer decline is massive habitat loss, rather than predation, and say that Colorado Park and Wildlife’s own research supports that thesis.
The agency’s studies seem like a thinly veiled attempt to appease hunters and blame predators rather than development, says Delia Malone, wildlife committee chair for the Sierra Club’s Rocky Mountain Chapter. “There’s a whole host of human causes that have diminished the ability for mule deer to thrive,” Malone says. “Historically, we’ve tried to scapegoat large carnivores as the bane of our existence.”
On the Roan Plateau, the seven-member field team is bundled up to ward off the numbing cold. At dawn it was 8 degrees, and in between helicopter drop-offs, the team members chat and stamp their feet to stay warm. Anderson wears a navy-blue baseball hat that hides his short silvery hair, and his light blue eyes squint in the cold sunlight. Before tackling Colorado’s mule deer problem, he worked with large carnivores in Wyoming in the 1990s, crafting the state’s first wolf plan and studying grizzlies and cougars, work that acquainted him with the politicized nature of wildlife management, especially when it comes to predator management in the West. He’s since studied energy development’s impacts on mule deer, along with restoration of the ungulates habitat, and now, predator control. “It makes it difficult to do objective research when you’ve got all these political entities pushing these different directions,” Anderson says. “We’re not pushing any agenda here; we’re just trying to learn how these systems work.”
The Piceance Basin, Colorado’s “mule deer factory,” is home to the state’s largest migratory mule deer herd. Mule deer are considered a good indicator species of ecosystem health because they require a wide array of plants for forage and shelter, including sagebrush, juniper, mountain mahogany and piñon trees – the same plants that other wildlife species, such as sage grouse, also rely on. The deer are also an important revenue source for the state, bringing in millions of recreation dollars annually from hunting and wildlife watching. Hunting licenses for all game species provide about 60 percent of the Colorado agency’s wildlife-related revenue, funding research, hatcheries and education.
Mule deer face some serious human competition. From 1980 to 2010, 2.5 million acres of their Colorado habitat were lost to housing development and oil and gas fields. The Piceance Basin, where Anderson studies mule deer, contains the nation’s second-largest natural gas reserve: It’s already dotted with oil and gas wells, and over the next 20 years, 15,000 more have been proposed by the federal Bureau of Land Management.
A study published in July by Colorado Parks and Wildlife, Colorado State University and the Wildlife Conservation Society found that both low-density rural housing and energy development harmed mule deer herds. It correlated 30 years of land-use changes with mule deer declines, finding that houses, roads and oil wells all encroached on the winter range essential to deer survival. Housing had the biggest negative effect on the number of deer, more than oil and gas development. But because researchers don’t know what specifically caused the decline – whether it was fragmented habitat, noise, reduced forage, or a combination of all three – they say the issue needs further study.
In the 1990s, following aggressive, state-funded feeding programs and predator control, the state’s mule deer population skyrocketed to over 600,000. But then, at the end of the decade, the population crashed, and since then it has continued downward. Since 2007, Colorado Parks and Wildlife has reduced the number of hunting tags by 85 percent to help their recovery. Statewide, the mule deer population in 2015 was at 436,000, below the 557,000-target range set by the agency.
The studies won’t be the first time the state has targeted carnivores in an attempt to hike deer numbers. In 1992, a predator-control study conducted in the Piceance Basin found that even after coyotes, the dominant predator in that area at the time, were reduced, many fawns died from disease or starvation, because the deer were at carrying capacity, at a population density three times higher than they are now. “They showed habitat conditions were the biggest limitations,” Anderson says.
Here on the Roan Plateau, researchers are seeing hefty fawns in the fall, and starvation is rare during winter. But fewer of the young deer are making it to winter in the first place; Anderson says about 50 percent of radio-collared fawns are eaten, primarily by mountain lions and black bears. Researchers will consider predator control a success if fawn survival increases by around 15 percent, determining whether predation is a main limiting factor for mule deer populations in those areas, or if other conditions, like habitat, would cause fawns to die anyway.
The predator removals by the state will start in spring 2017 and cost $4.5 million for both sites, partly funded by federal aid. Up to 25 black bears and 15 mountain lions (1-2 percent of either animal’s total state population) will be killed in May and June for three years in the Piceance Basin and the Upper Arkansas River. The predators will be caught by snares, traps or hunting dogs, and then shot. Parks and Wildlife says that it will use remote cameras at trapping sites to identify females with young and attempt to relocate the families at least 30 miles away instead of killing them; any female lions or bears that show signs of nursing will be released back into the area.
The study has been met with strong resistance from conservationists and Colorado scientists who have worked with Parks and Wildlife before. They say that the state agency’s new study is at odds with what its own past studies have found. “This seems both illogical and a waste of public funds,” wrote three scientists in a letter to the agency. “The scientific consensus is clear and compelling – predator control is a costly and ineffective management tool to increase mule deer populations.” Killing predators may temporarily boost mule deer numbers, but critics say it’s not a sustainable solution because it further disrupts an ecological system already off-balance from human activities.
Other Western states with the same problem have taken different approaches. A 2011 study in Idaho found that killing predators did not increase mule deer herds significantly; rather, severe winters and reduced forage were bigger problems. Utah has a $50 bounty on coyotes and contracts with Wildlife Services to gun down coyotes during the winter. But the state also has a habitat-restoration program and has seen mule deer numbers trend upwards the past five years, though no one is sure of the specific cause. In Wyoming, where populations dropped 39 percent from 1991 to 2012, ongoing research is looking at how much competition from elk is harming mule deer. But it’s difficult to extrapolate much from these place-based studies, because so many factors converge: habitat quality and quantity, disease, competition, predation, drought and severe winters. “What people in Colorado have to figure out is you can’t keep building and put in roads and pipelines without losing wildlife. It’s a zero-sum game,” says Barry Noon, one of the scientists behind the letter to the state wildlife agency.
If the three-year study proves fruitful in increasing fawn survival, predator control could be used as a way to boost mule deer populations in other places in the state. Either way, Anderson says the agency’s next research project will see if Colorado’s booming outdoor recreation scene – with its growing numbers of mountain bikers and hikers – affects mule deer and other wildlife. “This is true throughout the Western U.S.: There are lots of things that influence mule deer populations, and predation is just one of them.”