On a brisk summer morning, many moons ago, I awoke to the sudden pelting of pebbles on my sleeping bag. Rubbing sleep from my eyes, I rolled over to see my friend pointing wildly across the meadow. Tracking her silent gesture, I witnessed a stunning display of wildlife: two great Alces alces shirasi, the Shiras moose, slowly picking their way across the dewey alpine meadow. As we snuggled deeper into our bags, I was overcome with joy to have simply observed the moment.
Moose encounters are on the rise in Colorado, leading to questions about their origins, ecosystem stability and safety. Interestingly, moose are not native to Colorado. In 1978, 24 moose were transplanted to Colorado from Utah and Wyoming.
“Historical records dating back to the 1850s indicate that moose wandered into northern Colorado from Wyoming,” said Rachael Gonzales, Colorado Parks and Wildlife (CPW) northwest region public information officer. “But [they] were transient and never established a stable breeding population.”
In the 1950s, Colorado wildlife officials considered moose introduction for “hunting opportunities,” according to the National Park Service website. Formal discussions began nearly a decade later between the former Colorado Division of Wildlife (now CPW), U.S. Forest Service, Bureau of Land Management, National Park Service, local ranchers and the general public. Concerns were raised regarding winter foraging competition between elk, mule deer and moose, but aerial observations of Utah moose easily navigating deeper snow showed that they ultimately wintered in different areas. It was decided: Colorado’s remote North Park region near Walden in the Routt National Forest would be an ideal habitat for the large ungulate.
As expected, the original 24 moose thrived in northern Colorado. The area was essentially unoccupied, rich in the moose’s ideal diet of willow, fir and aspen, and natural predators, such as the wolf and grizzly bear, were absent.
In a 1988 Division of Wildlife report, entitled “Colorado Moose: Reintroduction and Management” and written by wildlife biologists André Duvall and the late Gene Schoonfield, it was found that by 1980, the cows had a twinning rate of 17% and averaged 95 calves per 100 cows. This birthing rate showed transplant success, and since “the public enjoys observing moose in the wild,” multiple Colorado counties expressed interest in moose introduction.
As the population soared, hunting was identified as the primary solution for population management once “the moose reached a verifiable 100 animals.” That number was achieved in 1985, and five licenses to hunt mature bulls were issued for Colorado residents during November, avoiding the rut.
Over the next four decades 235 more moose arrived in Colorado, including Garfield County, resulting in a current-day statewide population of around 3,000. In the Roaring Fork and Crystal River valleys, Gonzales said the local population is in alignment with the state’s growth trajectory and estimated that moose have increased three-fold over the past 20 years.

The human variable
Migrating from Grand Mesa and originating from a Utah transplant, local moose are categorized as the Shiras subspecies. The Shiras is the smallest moose, but still enormous. Bulls can range up to nine and a half feet long, six feet at the shoulder, and over 1,000 pounds. Top running speeds have been recorded at 35 miles per hour, making them a formidable opponent in a footrace.
Moose prefer to occupy dense forests near lakes and marshes where willow, their favored food source, is abundant. However, in the arid Southern Rockies, wetlands represent only about 2-3% of the landscape, raising concerns about over-browsing, explained Delia Malone, vice-chair of Roaring Fork Audubon and ecologist with the Colorado Natural Heritage Program.
“Moose introduction did not take into account the inappropriateness of the Southern Rockies,” said Malone. “Willow vegetation is critical for critters like beavers, who are important factors in maintaining and growing our wetlands, which so many riparian bird species absolutely rely on for their lives.”
In the Kawuneeche Valley of Rocky Mountain National Park, rigorous, long-term research has shown that as the moose population increases, critical vegetation declines. The moose are thriving and eating up to 60 pounds of vegetation daily. Without natural predators, Malone said moose face “bottom-up control” — a natural phenomena where an animal depletes its food source and is thus forced out or dies. Ongoing efforts for vegetation restoration are underway, but overconsumption leaves bare soil vulnerable to the warming climate, making it difficult for regrowth.
“Moose [introduction is] an additional component of why and how we have thrown natural systems out of balance,” said Malone. “To put our natural world back into balance, we need to be aware of the complexity and the value of all of the components of a natural ecosystem.”
She added, “In this particular case that means restoring our large carnivores, including wolves, to ecologically effective populations.”
Increasing moose numbers also means an increase in the potential for moose-human conflict. Off-leash dogs and moose interactions often have poor outcomes since moose instinctively react to dogs as they would a wolf. Moose are extremely territorial and will defend their area by either standing their ground or charging. If you encounter a moose, try to find an alternate route or allow the moose to leave the area. Signs of aggression, such as ears back, raised hairs and snout licking, mean you are too close. If the moose charges, run fast and hide behind a large object.
Moose populations are growing faster in Colorado than any of the other lower 48 states. Brought to a fragile ecosystem for the sake of human pleasure, the introduction’s impact is proving to be significant. Without human interference it is possible moose would have made it here eventually, but it would have been on their own terms and, possibly, in the natural order.