TREE SQUIRRELS OF CALIFORNIA

Welcome, Squirrel Friends and Foes!

We find ourselves in an odd situation here on the West Coast of the United States.

Many humans love seeing squirrels. So much so that when urban development pushed out our native species, well-meaning efforts brought in squirrels from east of the Mississippi.

Today, most squirrels seen in California’s cities, suburbs, campuses, and parks are not native.

What You’ll Find on This Site

Species profiles — photos and facts about each California tree squirrel, native and non-native
Identification guide — how to tell squirrels apart by appearance, behavior, and habitat
Our Evolutionary Ancestor — survival traits essential after the asteroid impact
Frequently asked questions — myths, facts, and common concerns
Additional resources — reports, squirrels in the news, and wildlife agency links

What’s Native ... and What’s Not?

Pacific Coast Native Tree Squirrels

Western Gray Squirrel (Sciurus griseus)
Douglas Squirrel (Tamiasciurus douglasii)

Western Gray Squirrel and Douglas Squirrel (click images for more info)

Non-native Squirrels - Introduced from Eastern US - early 1900's

Eastern Gray Squirrel (Sciurus carolinensis)
Fox Squirrel (Sciurus niger)

Eastern Gray Squirrel and Fox Squirrel (click images for more info)

Why Identify My Tree Squirrel?

Non-native squirrels typically cause more problems than natives!

It’s important to know what kind of squirrel you’re looking at. Some species can be managed with humane deterrents, but others are protected by law.

Knowing the difference matters.

The Squirrels Are Here to Stay

The Cute Factor: Public sympathy complicates management of charismatic invasive species.

Western Gray, Eastern Gray and Fox Squirrel

Squirrels' playful antics are endearing. That's why they were introduced in the first place. (see sidebar)

But when the squirrels get out of hand, as they do when introduced into a non-native habitat, they become too cute to remove. At T.S.O.C., we are advocates for squirrels, and now that the non-natives are here, we don't expect them to be "sent home." At the same time, they are displacing our native squirrels, so we are faced with a social, political and moral challenge.

“However, eradications of charismatic mammals may encounter strong opposition… Considering the case study of the eastern grey squirrel… when the model was expanded to integrate the attitude of citizens… citizens’ support was limited, and this resulted in a reduced overall utility of intervention.” La Morgia, Paoloni & Genovesi, 2016. PubMed

“The social acceptance of attractive invasive species with charisma is higher than that of unattractive invasive species… An appearance perceived as beautiful or cute can make the management of species invasions more difficult, because then public support is often lacking.” CABI News, summarizing research in Frontiers in Ecology and the Environment

What is a Tree Squirrel?

Tree Squirrels Nest in Trees

Tree squirrels typically build their nests in trees, rather than underground. They are agile climbers, have long bushy tails for balance, and rely on a tree canopy to stay safe from predators.

Close Cousins – NOT Tree Squirrels

Ground Squirrels and Chipmunks nest underground, have stripes or spots, and sport cheek pouches for food collecting.

Tree squirrels do not.

If it nests in a tree, it’s likely a tree squirrel.
If it lives underground or in rock piles, it’s probably a ground squirrel or a chipmunk.

Did you know?

California's native tree squirrels need connected tree canopies.

Why don't we see the native squirrels in our cities, suburbs and parks?

Eastern Grays were introduced in the early 1900s after habitat loss and disease reduced native populations on the West Coast. The native Western Gray squirrels need tree canopy to live and were pushed back with the receding forest as the cities and suburbs grew.

A mange epidemic compounded the loss, nearly destroying the Western Grays. City planners wanted to "re-nature" the cities and introduced the Eastern Gray Squirrel.

The urbanization of Eastern Gray squirrels was a national movement that had begun in Philidelphia, Boston, and Manhattan's Central Park, but humans had to provide the food for them to survive there, so their populations were contained. When they got out of hand (which they did) extermination efforts had little opposition - in fact, hunting the squirrels was embraced by many.

Western Grays are shy around humans but fierce when defending against the non-natives.

See the Research Studies

The Urban Pet

A Cultural Shift in American Cities

In the late 1800s and early 1900s, city parks were carefully designed as peaceful escapes from growing urban chaos.

Squirrels were intentionally added to these green spaces, first on the East Coast and soon after across the country. Squirrels were seen as 'morally upstanding citizens' - as living symbols of civility, kindness, and connection to nature.

Urban planners and park officials began introducing squirrels into public parks as part of broader efforts to cultivate green spaces and promote civic virtue. These efforts weren’t only aesthetic, they reflected a deeper cultural shift.

“The urbanization of the gray squirrel in the United States... was an ecological and cultural process that changed the squirrels’ ways of life, altered the urban landscape, and adjusted human understandings of nature, the city, and the boundaries of community.” Etienne Benson, Journal of American History

“The gray squirrel was seen as a particularly desirable park resident... an ‘elegant creature, so cleanly in its habits, so graceful in its carriage, so nimble and daring in its movements,’ one that ‘excites feelings of admiration akin to those awakened by the birds and the fairer forms of nature.’” John Burroughs, quoted in Benson, 2013

From Beloved to Blamed

When City Squirrels Wore Out Their Welcome

Early efforts to introduce squirrels into cities were idealistic, but short-lived in some places. Within a few years, the same animals celebrated as moral symbols and charming entertainers were suddenly viewed as destructive, lazy, or overfed nuisances. Cities responded swiftly.

In 1865, the squirrels of New Haven Green had ‘become so obese from good living that they are continually missing their hold and falling from the tree tops’
(Providence Evening Press, Nov. 3, 1865), quoted in Etienne Benson.

When insect populations rose in city parks, squirrels were unfairly blamed for eating the eggs of insect-eating birds. Such claims lacked scientific grounding and were discredited over time, but the squirrels were culled, nonetheless.

the squirrels must go

Gone as Quickly as They Came

“Philadelphia’s squirrels were captured or killed, their nest boxes were removed, and the city made an attempt to establish insectivorous European and American songbirds in their place.” Etienne Benson, Journal of American History

In those days, city parks were not designed with animals in mind. The trees and plantings offered little in the way of food or shelter, so the squirrels relied on handouts from visitors. When that feeding ended, there was nothing in the parks to sustain them, and they were left to forage wherever they could — often in trash bins and street refuse.

“Boston’s experiment with squirrels also came to an end... the squirrels simply died out.” Benson, 2013

“Squirrels were increasingly accused of becoming ‘lazy’ or ‘pauperized’ and dependent on human handouts during the winter.” Etienne Benson, quoting contemporary press reactions

Even Central Park, which had the most success with the squirrel re-wilding movement, took measures to cull them. Officials launched early-morning hunts, with no public outcry.

“Despite opposition... a series of early-morning hunts... resulted in a take of ‘fully a hundred fine fat squirrels.’” Etienne Benson, Journal of American History

Then the tide turned. Frederick Law Olmsted began a new era of park design in the U.S., shaping places where trees could thrive—and squirrels could live without handouts. In the early 1900s, his work helped remake parks into wooded retreats, not just for people, but for animals too.