Invasive Fox Squirrels Move into Utah, Pushing out Native Red Squirrels 

Fox squirrels, the largest tree squirrels in North America, have made their way into Utah and are quickly becoming noticeable residents along the Wasatch Front. According to Utah State University Extension wildlife specialists Nicki Frey and David Stoner, these orange-bellied squirrels (Sciurus niger) were first seen in Utah in 2011 and have become increasingly pervasive in the Salt Lake City area.

Although they are native to the eastern United States, fox squirrels have gradually migrated west into Colorado and Utah. They are easy to distinguish from the native red squirrels (Tamiasciuris hudsonicus), Utah’s only native tree-dwelling squirrel. At 17 to 28 inches long, fox squirrels are substantially larger than the 11 to 14-inch native red squirrels. Red squirrels are grayish-red with white bellies. Fox squirrels have bushy red tails and red bellies. Also, unlike rock squirrels, which live in burrows among cliffs and boulders, fox squirrels nest and spend most of their time in trees.

Fox squirrels have adapted well to Utah’s urban landscape, thriving in neighborhoods filled with oaks, maples, and other food-bearing trees. They prefer to nest in tree cavities but will construct leafy nests when needed. According to Stoner, in Utah, most litters are born between February and April, though in warmer areas, or years with abundant food, fox squirrels may produce a second litter in the fall.

While their adaptability makes them successful survivors, it also brings them into conflict with people. Fox squirrels can cause significant damage to yards and orchards by eating fruit, stripping tree bark, digging up lawns, and chewing irrigation lines and cable wires. 

“They can become quite a nuisance if left unchecked,” Frey said. “They also compete with our native red squirrels, which are only half their size and less aggressive. They may overlap in urban areas within the mountainous areas of Utah, where red squirrels are commonly found.”

Frey said red squirrels are an important part of Utah’s native ecosystem, balanced with the plants and animal species in its community. Fox squirrels aggressively oust red squirrels when they are in the same area, stealing their nests and food. Through their foraging process, red squirrels distribute a native fungi that is critical to the health of our forests. Conversely, fox squirrels harbor a disease that can kill red squirrels. The loss of red squirrels from an area can mean the loss of forest health. 

“Because fox squirrels readily adapt to eating human-sourced food and thrive in urban areas, they can exist at higher densities than red squirrels,” Frey said. “With their much larger body and litter size, this means they have the potential to cause more damage to human resources than red squirrels.”

Frey and Stoner recommend several management strategies, including exclusion, habitat modification, and trapping. Simple steps such as installing wire-mesh fences around garden boxes, trimming tree branches away from houses and power lines, and using smooth metal barriers on tree trunks can help deter squirrel activity. Covering fruit trees or gardens with fabric netting can also provide temporary protection during ripening seasons.

Lethal traps may be used legally since fox squirrels are considered an invasive species in Utah and are therefore not protected by state law. Traps should be set carefully to avoid harming native species, birds, or pets. Lethal traps should not be used in areas that also have red squirrels; it is not legal to lethally trap red squirrels. Live traps are also an option. Note that moving trapped animals to new environments is not permitted due to ecological risks and low survival rates for relocated animals. Translocated animals may also spread disease. Exceptions exist for species with conservation status, such as the Utah prairie dog and beavers, which may be relocated by wildlife professionals only. In such cases, residents should contact UDWR regional offices for assistance.

Most trapped nuisance wildlife are euthanized. There are humane and ethical ways to do this, and, in most cases, state agencies will assist. A publication by USU Extension colleagues Nicki Frey and Cory Farnsworth gives specific guidelines on euthanizing and disposal of nuisance wildlife.

Utah residents can assist scientists in tracking fox squirrel expansion by reporting sightings to the Utah Natural Heritage Program.

Find out more information about fox squirrels.