Discover the lively world of Riverside's most frequent wildlife visitors—eastern fox squirrels and California ground squirrels. Learn about their habitats, behaviors, and the unique challenges they pose in our neighborhoods, all while appreciating their role in the city’s diverse ecosystem.
One of Riverside's most frequent wildlife encounters is with our squirrels. The two large squirrels are the eastern fox squirrel (Sciurus niger = "The black squirrel," even if it is all black in a tiny part of its range) and the California ground squirrel (Otospermophilus beecheyi = "Beechey's eared seed-lover"). The fox squirrel is the one that occurs in the well-treed parts of town (e.g. the Wood Streets, Fairmont Park). The ground squirrel is abundant in natural areas and adjacent neighborhoods (Sycamore Canyon Park, Tequesquite Arroyo, Hidden Valley, etc.). A friend lives a few blocks from the Box Springs Mountains and reports fox squirrels in her backyard and ground squirrels in her front yard!
Both species are what most folks would consider typical squirrels, good-sized fluffy rodents with bushy tails. The squirrel family includes tree squirrels, ground squirrels, mini-squirrels like chipmunks, flying squirrels (Rocky!), and some not-so-squirrely species, like groundhogs, prairie dogs, and marmots.
(Courtesy of Mark Winford)
In case you aren't sure which is which, there are several ways to distinguish these guys. The eastern fox squirrel is a tree squirrel, the biggest tree squirrel in North America, about 20-30 inches from nose to tail tip. If not in a tree, fox squirrels are rarely far from a tree. In my neighborhood, the only time I note one more than a couple of dozen feet from a tree is when it is trying, kamikaze-style, to cross the street, often hesitating directly in the path of my car! Fox squirrels have brown-gray coats with golden-creamy undersides. When a fox squirrel sits, it often loops its luxuriantly bushy tail into a question mark. For shelter, fox squirrels build leafy nests in trees or use natural cavities.
The smaller California ground squirrel is about 18 inches long. The ground squirrel is often found, well, on the ground, underground, or perched on a boulder. Likewise, they are well-spaced atop fence posts on Interstate 5 through the San Joaquin Valley. California ground squirrels are a mottled mix of gray and light brown on the back and lighter below. The neck and shoulders have a whitish mantle. Their bushy tail is far from luxuriant, more bottlebrush-like or what you might expect from a fox squirrel with a mild case of the mange. The tail flops when the California Ground Squirrel is sitting. California ground squirrels spend a lot of time building or hanging out in their burrows.
The California ground squirrel is a California old-timer, part of the native fauna for thousands of years. The eastern fox squirrel is a carpet-bagger; it has been living in SoCal only 120 years. It is native to the eastern half of the United States, from North Dakota and New York south to Texas and Florida. In 1904, Civil War veterans at the Sawtelle Veterans Home near Westwood pined for the native squirrels of the East. According to some accounts, the veterans simply wanted to make their surroundings a bit more like where they grew up; others say they missed eating squirrel stew. In any case, the introduced squirrels escaped or were released. They found the Southland to their liking.
The range of the fox squirrels expanded mostly east and west. They were established in Hollywood in 1947 and in Oxnard in 1970. In 2002, they took up residence in an area as far south as Irvine. By 2004, they had made it to Claremont. It's hard to say exactly when they got to Riverside, but by 2012, they were present in great enough numbers to start annoying some Riversiders. In 2015, the squirrels proved pesky enough that the Riverside City Council passed an ordinance allowing city residents to trap and kill (but not shoot) the critters. Because of other city and state laws restrict their control within the city to humane traps for release elsewhere or lethal traps for a permanent solution.
Eastern fox squirrels dine on various fruits, seeds, nuts, and flowers. Avocadoes are a favorite. Annually, they harvest mandarins from our seedless Kishu Tree and appear to grin as they peel and munch the fruits on our patio table. They can wreak havoc in flower beds by burying acorns at one time of the year and harvesting the cached nuts later. They can dominate bird feeders, leading to the invention of "squirrel-proof" feeders, including battery-powered feeders that spin when activated by a weight sensor, thereby flinging unsuspecting squirrels. Fox squirrels even eat things that offer no nutrition.
About a dozen days into working on this article, our landline and internet went out simultaneously. Troubleshooting by phone revealed the problem was outside. A few days later, an AT&T repairman started tracing the problem and realized several homes over multiple blocks had the same problem. After climbing a pole, it was found that one or more fox squirrels had stripped a long stretch of fiber optic line of its protective coating. He reported that such squirrel-based problems are not uncommon. My guess is that, like other rodents, squirrels have teeth that grow continuously and need the right texture to wear them down – even if it's a synthetic coating on fiber optic lines.
(Courtesy of William M. Cornell and Linsee Ramsay)
Likewise, California ground squirrels are sometimes far from angels. They are a long-standing California agricultural pest (Grinnell and Dixon 1918). Ground squirrel burrowing can ruin gardens and threaten foundations. Roger and Connie Ransom watched a potted tree begin to list increasingly on their brick patio nested in the sand. When it reached a crazed angle, they inspected the patio to find a portion undermined by a "city" of ground squirrel tunnels through the soft sand, requiring an eviction and patio makeover to exclude future subterranean tenants. Likewise, ground squirrel foraging and burrowing can disrupt gardens. Ground squirrel control is straightforward and largely legally unrestricted (pngroundsquirrel.pdf (ucanr.edu).
Do squirrels have natural enemies? For tree squirrels, these would include cats, owls, and hawks. I have noticed an increase in the Cooper's Hawk population in the Wood Streets concurrent with Riverside's squirrel invasion. Predators of California ground Squirrels include hawks, owls, coyotes, badgers, cats, dogs, raccoons, and snakes, particularly rattlesnakes.
The non-native eastern fox squirrel might be perceived as an exotic introduced species, making it "invasive." The California ground squirrel is a native. This couple of species illustrates that whether a species is "good" or "bad" depends less on how they got someplace and more on how they interact with humans and human values. For example, the fox squirrel eating the eggs of our favorite birds, nibbling on fiber optic lines, or digging up a lawn might be seen differently than the fox squirrel eating the eggs of noxious birds or capering in the back yard or simmering in the stewpot. Likewise, a California ground squirrel family reducing a population of weeds might be seen in a different light than a family eating up a recently planted crop. The context is what conservation decision-makers call the "human-natural interface" matters.
At the moment, both species of squirrels are here to stay as part of Riverside's natural environment. Until Riverside is paved end-to-end, eastern fox squirrels will persist in our forested neighborhoods, and California ground squirrels will persist in natural vegetation and nearby neighborhoods. Both species will occasionally present challenges, but at the same time, we can appreciate them as part of the diversity that is naturally Riverside's.
Resources Used for This Article
Grinnell, J., and J. Dixon. 1918. Natural History of the Ground Squirrels of California. Monthly Bulletin of the State Commission of Agriculture 7:597-708.
Norm Ellstrand is an emeritus Distinguished Professor of Genetics and former Director of the California Agriculture and Food Enterprise at the University of California Riverside.
Dr. Howard Brett Frost’s groundbreaking citrus research, including the Frost Washington Navel Orange, transformed the industry and continues to impact the fruit we enjoy today.
