Four resident species share California's forests, parks, and neighborhoods. Two are native to the state, two were introduced from the eastern United States.
Sciurus griseus
A shy forest and oak-savannah dweller with elegant silver-gray fur, a white belly, and an extraordinarily lush, feathery tail. Requires large connected tree canopies to survive.
One combination no other California tree squirrel shares.
The Western Gray is still widespread up and down the Pacific Coast, from Baja California into British Columbia. Yet many Californians have never knowingly seen one, because it does not live where most of us live. Washington's wildlife biologists describe the species as "typically secretive and wary by nature," and it rarely habituates to people the way the Eastern Gray does. It is a squirrel of the canopy. It avoids large open spaces, travels tree to tree, and is almost always within a second or two of a trunk, whereas a lawn, a road, or an open lot is a barrier it will not readily cross.
The introduced squirrels have no such rule. Eastern Grays and Fox Squirrels cross open ground freely and are perfectly comfortable in a city. So when development fragments the canopy, the two species respond in opposite ways. The Western Gray retreats to wherever continuous canopy remains. The Eastern Gray moves into the gaps. A multi-year study in the Santa Cruz area (Jessen et al. 2018) found that in developed, fragmented forest the Eastern Gray does not merely outlast the native squirrel but actively excludes it from viable habitat, and identified the Eastern Gray as a "driver" of the Western Gray's decline. In Southern California, Fox Squirrels have replaced Western Grays in lowland oak woodlands wherever those woodlands became urbanized (Cooper and Muchlinski 2015).
Habitat loss alone would not have done this. Western Grays withdrew because they are wild, and the newcomers thrived because they are not. In Washington the combination has been severe: forest clearing has isolated populations from one another, introduced squirrels have moved in, and the state now lists the species as endangered, uplisted from threatened in 2023. Oregon classifies it as a vulnerable sensitive species, a step short of that. It is not protected under the federal Endangered Species Act. California still holds the species in real numbers, but in quiet, heavily wooded country and along the wildland edge, which is to say, not where most people are looking.
The species ranges from the Sierra Nevada foothills and coastal ranges of California through Oregon and Washington into Baja California Norte. In southern California, populations are largely restricted to mountain ranges and surrounding foothill communities with intact tree canopy.
Western Gray Squirrels appear docile and keep their distance from people, but in the forest they are fierce and highly territorial. Studies at Griffith Park show they actively displace Fox and Eastern Gray Squirrels from prime habitat, forming a living buffer that also shelters the smaller Douglas Squirrel.
Searching "Western Gray Squirrel" on major stock photo platforms returns the wrong species most of the time, sometimes tagged with the correct scientific name Sciurus griseus while showing a Fox or Eastern Gray. An audit across three platforms found mislabeling rates of 78–95%.
The Western Gray Squirrel remains widespread across much of California, Oregon, Washington, Nevada, and Baja California Norte, and is not currently listed under the U.S. Endangered Species Act. Conservation organizations and state wildlife agencies report continuing declines across portions of its range.
Ongoing challenges include habitat loss, fragmentation of forest canopies, disease outbreaks such as notoedric mange, and competition from introduced Eastern Gray and Fox Squirrels. In urban areas, introduced species have displaced Western Grays from parks and residential neighborhoods, restricting many native populations to larger forested habitats where continuous canopy remains intact.
Conservation efforts focus on maintaining connected tree canopies, protecting oak woodland and conifer habitats, and limiting the spread of introduced squirrel species in areas occupied by native populations.
NatureServe currently ranks the Western Gray Squirrel as globally secure (G5), while recognizing regional declines and conservation concerns in portions of its range.
Tamiasciurus douglasii
Small, bold, and impossibly loud, the Douglas Squirrel is the sound of California's conifer forests. Half the size of the other tree squirrels, with a coat that shifts color with the seasons. Found only where conifers grow.
Small, warm-colored, and unmistakably loud.
The Douglas Squirrel is native to the Pacific Coast of North America, named after the botanist David Douglas, who explored the Pacific Northwest in the 1820s. In California, it is found in the Sierra Nevada, the Coast Ranges of the north, and the Cascades, closely tied to wherever conifers grow.
Unlike the Western Gray, which can use oak woodlands and mixed-forest edges, the Douglas Squirrel is almost entirely dependent on conifer habitat. Its range in California can reach sea level in the northern part of the state, but it keeps to the higher elevations in the south, and can be found in high forests as far south as Baja California.
In The Mountains of California (1894), Muir wrote of the Douglas Squirrel: "He is, without exception, the wildest animal I ever saw — a fiery, sputtering little bolt of life, luxuriating in quick oxygen and the woods' best juices." He called it "the mocking-bird of squirrels" for its astonishing vocal range. That characterization still holds today.
The Douglas Squirrel is the only California tree squirrel whose belly color changes seasonally: creamy beige in winter and spring, shifting to a warm burnt orange by late summer and fall. The upper coat also deepens in tone. The mechanism reflects hormonal and molting cycles timed to the conifer forest calendar.
The Douglas Squirrel is not currently listed as threatened or endangered at the federal level. Its deep dependence on conifer forest habitat, particularly old-growth and mature second-growth stands, makes it sensitive to timber harvest, wildfire, and forest fragmentation. Where large conifers remain, the Douglas Squirrel remains a reliable presence.
Douglas-fir seeds are winged and travel mainly on the wind. Douglas Squirrels cut the cones and store them unopened in cool, moist middens. That keeps the seeds fresh for the squirrel, but there is little evidence that cached cones grow into new trees, and forest researchers count this caching among the causes of seed loss.
Fungi are a large part of the diet. In a study in Lassen County, California, they made up between a third and nine-tenths of the squirrels' monthly stomach contents, including underground truffles. The squirrels spread the spores of these fungi in their droppings, and many are mycorrhizal: they grow in partnership with tree roots. Douglas Squirrels are also reported to hang mushrooms in branches to dry, a habit well documented in their close relative, the American Red Squirrel.
Eating fungi is an old habit among mammals. After the asteroid impact 66 million years ago, the small mammals that survived may have relied partly on fungi and insects, long before the first squirrels appeared. More on that, and on other animals that dry their food, on the Squirrel Evolution page.
Sciurus carolinensis
A curious, persistent, and people-friendly squirrel strongly associated with city parks, campuses, and urban neighborhoods. Frequently featured in urban wildlife studies and behavioral research, and frequently mistaken for California's native Western Gray Squirrel. Notable for an unusually wide range of color forms.
Many people are surprised to learn that California has both a native Western Gray Squirrel and an introduced Eastern Gray Squirrel. Because the two species are similar in size and both often show a gray coat with a white belly, they are easily taken for the same animal.
All four are Eastern Gray Squirrels, the same species.
Eastern Gray Squirrels show more color variation than any other tree squirrel in California. The white individuals seen in some parks are almost always leucistic (white coat, normal dark eyes), not true albinos, which are far rarer and have pink or red eyes. The black form is melanistic, caused by a variant in the MC1R gene. All are the same species.
In California, Eastern Gray Squirrels are found almost exclusively in urban and suburban settings: city parks, campuses, residential neighborhoods with mature deciduous trees, and landscaped green spaces. They have not spread broadly into the conifer forests, oak woodlands, or wildland areas where native squirrel species are established.
Known populations include Sacramento, parts of the San Francisco Bay Area (particularly south of the Golden Gate), the East Bay, Santa Cruz, and Stockton. Their range in California is more geographically limited than the Fox Squirrel's, though populations can be dense in the urban areas where they occur.
Eastern Gray Squirrels are the squirrels most commonly photographed, hand-fed, and featured in viral videos. Eastern Grays habituate to people readily; it is part of who they are. One study even found that Eastern Grays living among people, on university campuses for example, carried lower baseline stress hormones than those in wilder habitat (Rimbach et al. 2022). That comfort makes them far more visible than the native species. In California, most people who "see squirrels" in the city are seeing Eastern Grays, not Western Grays.
Black squirrels are Eastern Grays. The melanistic form results from a Mendelian MC1R gene variant and appears at higher rates in some urban populations than in rural ones. Many people who encounter a black squirrel assume it is a different species. It is not.
The Eastern Gray Squirrel is native to the deciduous forests of eastern North America, from the Great Plains east to the Atlantic coast. It was introduced to parts of the Pacific Coast, including California, in the late 19th and early 20th centuries, typically through deliberate releases in city parks.
In California, established populations occupy urban and suburban environments in the Bay Area, Sacramento Valley, and Central Coast. Their range is more geographically limited than the Fox Squirrel's, but populations can be dense and conspicuous where they occur.
In the urban areas where Eastern and Western Gray Squirrels overlap, Eastern Grays have displaced Western Grays in many neighborhoods. A multi-year study in the Santa Cruz area found that Eastern Grays can competitively exclude Western Grays from developed, fragmented forest (Jessen et al. 2018), suggesting they may pose a greater long-term challenge to California's native tree squirrels than previously recognized.
Management of Eastern Gray Squirrels in California requires a permit from the California Department of Fish and Wildlife if land or property is being damaged.
Sciurus niger
The largest tree squirrel in California and the dominant squirrel across much of Southern California’s cities and suburbs. Fox Squirrels thrive in human-altered landscapes and continue expanding through many urban regions of the state. Identified by vivid rusty orange tones that no native California squirrel shares: most visibly, an orange belly and a broadly rusty orange tail. Brought to California in the early 1900s and now well established across much of the state, the Fox Squirrel is considered a significant pest species.
The Fox Squirrel is frequently encountered alongside Eastern Gray Squirrels in Southern California parks and neighborhoods. Both are introduced species sharing the same urban habitat, but the Fox Squirrel is unmistakably orange where the gray squirrels are not.
The Fox Squirrel has a broader urban footprint in California than the Eastern Gray Squirrel. Populations are firmly established throughout Southern California (Los Angeles County, the San Gabriel Valley, Orange County, and surrounding areas) as well as in the San Francisco Bay Area, the Sacramento Valley, and other scattered urban centers. Their range continues to expand into suburban and foothill environments.
In much of Southern California, the Fox Squirrel is the most visible tree squirrel in parks and neighborhoods, so common that many residents assume it is native. The native Western Gray Squirrel is still present in surrounding wildland and foothill areas but has largely withdrawn from the urban core, which the introduced species now dominate.
"Of the four tree squirrels, the eastern fox squirrel is by far the most serious pest to homes and gardens in urban and suburban situations. In some cities, eastern fox squirrels have moved outward into agricultural land where they have become a pest of commercial crops."
University of California — Agriculture and Natural Resources, UC IPM Pest Notes: Tree Squirrels
The Fox Squirrel's size, confidence around people, and willingness to enter structures make it the most frequently reported squirrel pest in California. It causes damage to buildings, gardens, and commercial crops at a rate exceeding all other tree squirrel species in the state.
The first documented release of Fox Squirrels in California occurred around 1904 at the Veterans' Home in Sawtelle, in what is now West Los Angeles. Civil War and Spanish-American War veterans had brought them from the Midwest as pets and released them on the grounds.
From that single origin point, Fox Squirrels have spread across Southern California over the following century, a textbook example of how a small, localized introduction can establish a permanent wild population.
The Fox Squirrel is native to the eastern and midwestern United States, from the Great Plains east to the Atlantic coast. It was introduced to California in the early 20th century and has since established populations across much of the state's urban and suburban landscape.
Unlike the native Western Gray Squirrel, which requires connected forest canopy and is sensitive to habitat fragmentation, the Fox Squirrel thrives in the fragmented, human-altered environments of California's cities and suburbs. Its comfort with people, willingness to den in structures, and broad diet make it exceptionally adaptable.
Fox Squirrels have been documented displacing native squirrel species from urban parks and edge habitats. In areas where they co-occur with Western Gray Squirrels, competition for food and nesting sites may disadvantage the native species.
Management of Fox Squirrels in California does not require a permit from the California Department of Fish and Wildlife if land or property is being damaged. Legal lethal control methods must be observed.
This page covers California's four resident tree squirrel species. California is also home to Humboldt's Flying Squirrel, several ground squirrel species, and chipmunks, all members of the squirrel family, but ecologically and behaviorally distinct from the arboreal species covered here.
Those species are covered in the FAQ: flying squirrels and ground squirrels and chipmunks.
Other Squirrels of California →
.jpg){kind=link}