Virginia Opossums (Didelphis virginiana) are found in Wyoming, but they are not a stable, permanent part of the state’s wildlife. The species, often called a “possum,” is a marsupial that has been steadily expanding its range northward. While individual animals are occasionally sighted, Wyoming’s harsh climate prevents them from establishing self-sustaining populations. Their presence is generally considered transient, with animals migrating or hitchhiking from states further south and east.
The Confirmed Status of Opossums in Wyoming
The Wyoming Game and Fish Department (WGFD) does not recognize the Virginia Opossum as having an established, wild population within the state. They are officially classified as a non-native species. Individuals found are considered peripheral wanderers or transient arrivals, reflecting a lack of successful, long-term breeding groups capable of surviving the state’s winters.
The opossum’s presence is often an extension of population growth in adjacent states like Nebraska and Colorado, where the species is well-established. These animals are typically solitary explorers pushing the boundaries of their natural range. Because they are non-native, their importation or possession as live warm-blooded wildlife is heavily regulated and requires a state permit. Occasional sightings represent a failure to colonize the state rather than a successful range expansion.
Specific Geographic Areas of Sighting
Opossum sightings in Wyoming are heavily concentrated in the southeastern corner, particularly in counties bordering Nebraska and Colorado. Regions like Goshen and Laramie County, which includes Cheyenne and Pine Bluffs, report the most frequent encounters. This geographical pattern results from the species migrating from established populations immediately across the state lines.
Sightings are also clustered around urban centers and major transportation corridors, such as Interstates and rail lines. Opossums are known to be opportunistic hitchhikers, sometimes traveling long distances unknowingly within trucks or trains. Individuals have been found as far west as Rock Springs in Sweetwater County, suggesting arrival by vehicular transport outside the typical migration path. These sightings illustrate the transient and accidental nature of the opossum’s wider distribution.
Limiting Factors to Opossum Survival
The primary barrier preventing the opossum from establishing a stable population across Wyoming is its poor physiological tolerance for prolonged cold. Unlike many northern mammals, the Virginia Opossum does not hibernate and possesses poor fur insulation. Their internal metabolism is insufficient to generate the heat needed to survive extended periods of sub-zero temperatures.
The most visible sign of this cold sensitivity is the vulnerability of their bare, uninsulated extremities (tail, ears, and toes), which are highly susceptible to frostbite. This damage severely limits an animal’s ability to forage and reproduce, leading to high mortality rates during winter. Opossums must drastically reduce activity when temperatures drop below freezing, often struggling to forage when the maximum daily temperature does not exceed 0°C (32°F).
For a population to become stable, juvenile overwinter survival must be high enough to replace the adult population, but Wyoming’s extreme winter conditions make this nearly impossible. Deep snow and prolonged cold periods dramatically reduce the foraging success for the omnivorous marsupial, often leading to starvation. This combination of inadequate physiological defense and limited access to food ensures the species remains a rare and transient visitor rather than an established resident.