Who, What, Where, When, and Wolverines in Colorado
- Tim
- Feb 24
- 5 min read
In 2024, the Colorado General Assembly passed a bill authorizing the reintroduction of North American wolverines (Gulo gulo) back into the state. In January, Colorado Parks and Wildlife (CPW) published the Colorado Wolverine Reintroduction Plan. Due to Park County's remote, high-elevation environment, it is likely wolverines will call South Park home in the near future.
Who is the Wolverine
Despite their resemblance to bears, wolverines are part of the weasel family and are more closely related to badgers, ferrets, and otters. They weigh an average 40 pounds and measure 30 inches from head to the base of their tail - about the size of a border collie.
Today, wolverines can be found in the northwestern contiguous states, Alaska, Canada, Russia, Norway, Sweden, Finland, China, and Mongolia.
They are listed as federally threatened and endangered by the State of Colorado.
Wolverines have historically inhabited Colorado, but were extirpated in the early 1900s due to hunting, trapping, and poison baiting common to eliminate predators at the time. Ever since, only a few potential tracks and observations have been made in the state. Colorado does not currently have a breeding population of wolverines.
What is Their Ecological Significance
Wolverine behavior is well personified by the X-Man of the same name: ferocious and nearly indestructible, but highly reclusive, avoiding people and confrontation whenever possible.
While a wolverine is capable of taking down prey multiple times their size, including deer, they are primarily scavengers. Scavengers do one of nature's most important dirty jobs by consuming carrion that can harbor disease while cycling nutrients back into the ecosystem. Wolverines also help manage rodent populations.
Wolverines thrive in the high elevation mountainous habitats that make up much of Colorado. Studies suggest that they take advantage of harsh environments where spring snow persists because other predators struggle to compete. They between alpine habitats above timberline during the summer to hunt live prey and subalpine forests in the winter to scavenge winterkill - a testament to their tenacity.
Despite their small size, wolverines have large home territories. Adult female territories average 60 - 250 square miles (100 - 400 square kilometers) and do not typically overlap. This is similar to the home range of female grizzly bears or Zion National Park. A single male's territory will overlap with 2 - 3 adult females. They move across rugged terrain quickly, capable of traveling 95 miles (150 kilometers) in a single week. The Restoration Plan estimates that Colorado could sustain approximately 100 wolverines when their population stabilizes.
Where Will the Wolverine be Reintroduced
There is not a lot of research on wolverine reintroduction. Therefore, this effort will be a valuable learning experience for wildlife biologists globally.
To determine where reintroduction may be most successful, CPW generated 300 square kilometer hexagons across suitable Primary Habitat to model potential adult female territories. From these, CPW identified three Release Zones:
Northern Zone includes the mountainous region north of Interstate 70
Central Zone sits south of I-70 and north of Highway 50
Park County is the northern and easternmost portion of the Central Zone, which includes the Mosquito Range and Boreas Pass.
Southern Zone encompasses the San Juan Range of southwest Colorado, south of Highway 50
CPW has not yet determined where wolverines will be relocated from.
When - We're Up First
The Reintroduction Plan indicates that the first round of releases will occur in the Central Release Zone staring in 2027, followed by the Southern then Northern Release Zones in subsequent years. Approximately 15 wolverines will be released each year.
CPW has not yet publicly stated where the releases will actually occur. However, the Reintroduction Plan outlines CPW's strategy, which includes an adaptable multi-tiered approach:
Wild Births protocol will be initiated around February 1. This involves releasing pregnant females into a den-like structure with an ungulate carcass in or near the den to promote success.
Captive Births protocol comes next. These females will have pups in captivity, and the family group will be released near active marmot colonies around June 1.
Females without litters will be released following acclimatization.
Males will be captured and released near a female that his original home range overlapped with, unless antagonistic behavior is observed in captivity.
What does that mean for us in Park County and other communities in wolverine habitat?
Based on CPW's timeline, and typical dispersal rates, it is possible that wolverines will live in Park County by the end of the decade. If the 2027 release occurs in the western portion of the Central Zone, further from Park County and where the largest contiguous habitat exists, we might expect to see wolverines move into the Park County within 5-10 years.
There are still a lot of hurdles to overcome, such as permitting, governmental coordination, and the successful transfer and survival of animals. CO Rev Stat § 33-2-105.9 states that reintroduction will not occur until the Colorado population of wolverines is designated as a "non-essential experimental" population under the Endangered Species Act. This affords greater flexibility in how wolverine populations and their habitats are managed.
Considering Park County's rich ranching heritage and the controversial grey wolf reintroduction starting in 2023, many may wonder if the proliferation of wolverines may be a new threat to their families, pets, or livestock.
Luckily, due to their solitary nature, human-wolverine conflicts are virtually nonexistent. Wolverines prefer to avoid human settlements. Conflicts between wolverines and pets are rare. Pet owners with small dogs and cats should keep their pets indoors or a secure location when unattended, which is already good practice living in an area with coyotes, bears, bobcats and mountain lions.
There is a small threat to livestock, particularly sheep, and wild ungulates. Full grown cattle and elk are too large for wolverine to prey upon. While not as widely reported, it should be noted that goats, chickens, and ducks are small enough to be potential prey and should be appropriately secured for protection.
There is some depredation recorded on newborn elk, deer, bighorn sheep, mountain goats and moose; however, these incidences tend to be opportunistic and do not occur frequently enough to impact wildlife populations. Wolverines much prefer to consume carcasses left behind by larger predators capable of taking down a big meal. While newborn cattle may be at risk, "calves are generally large enough to avoid predation by the time they are turned out in alpine areas where wolverines exist" (Reintroduction Plan). Ranchers and livestock owners may reduce predation risk by avoiding pasture-based birthing and neonatal rearing in areas occupied by wolverines and other predators.
Ultimately, the impact of wolverine reintroduction to high mountain living will likely be negligible. Few of us will even spot our new neighbors in the wild. While we may not see them, they will be working to control rodents, including the packrats that like to occupy our engine bays, and breaking down carcasses of animals that do not make it through our harsh winters.
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