The vibrant urban environment of Phoenix, Arizona, may seem like an unlikely place for squirrels to thrive, yet these resilient rodents are a common sight across the metropolitan area. Despite the Sonoran Desert’s arid climate, several species have successfully adapted to the city’s unique micro-habitats, utilizing the resources provided by landscaped parks, golf courses, and residential backyards.
Species Found in the Phoenix Area
The most frequently encountered ground squirrel in the Phoenix area is the Harris’s Antelope Squirrel (\(Ammospermophilus harrisii\)), a species native to the southwestern United States. This small, fast-moving rodent is often mistaken for a chipmunk due to its size and the single, narrow white stripe running along each side of its grayish-brown body from shoulder to rump. Unlike a chipmunk, however, the Harris’s Antelope Squirrel lacks stripes on its face and frequently carries its short, bushy tail arched over its back as it darts across the ground.
Another prominent species is the Rock Squirrel (\(Otospermophilus variegatus\)), which is the largest ground squirrel found in the region, weighing up to 1.5 pounds. Rock Squirrels have mottled brownish-gray fur and a long, bushy tail, giving them an appearance similar to that of a tree squirrel. They are often seen in areas with rocky outcrops but have readily moved into urban settings, utilizing human-made structures like retaining walls and foot bridges for burrowing. While tree squirrels like the Eastern Fox Squirrel (\(Sciurus niger\)) are not native to Phoenix, they have established localized populations in other parts of the Sonoran Desert due to human introduction and may be occasionally found in heavily vegetated urban corridors.
Surviving the Urban Desert Heat
Harris’s Antelope Squirrels, for instance, are known for their unusual diurnal activity, often scampering about even in the hottest part of the day. When their body temperature reaches its upper limit, they engage in a behavior known as “heat dumping.” They retreat to the shade and press their belly against the cooler ground to rapidly transfer excess heat away from their body.
Rock Squirrels and other ground dwellers primarily use their extensive burrow systems as a thermal refuge, retreating underground during the most intense midday heat. In the urban environment, these burrows are frequently excavated beneath concrete slabs, irrigation ditch banks, and artificial rock formations, which offer a more stable and cooler temperature than the open desert soil. They adjust their schedule to be most active during the cooler early mornings and late afternoons, utilizing the shade provided by non-native trees such as palm and citrus trees common in urban landscaping. These animals also obtain much of their necessary moisture from succulent vegetation, supplemented by artificial water sources like lawn irrigation and standing water.
Origin and Local Status of the Species
The presence of squirrels in the Phoenix area is largely a result of native species adapting to human-created habitats. Both the Harris’s Antelope Squirrel and the Rock Squirrel are indigenous to the Sonoran Desert and surrounding southwestern ecosystems. Their historical range naturally encompasses the area where the city of Phoenix developed, meaning they adapted to the rapidly changing environment rather than migrating into the region.
Urbanization, with its reliable access to water and non-native food sources, has inadvertently supported and expanded the populations of these native species. Rock Squirrels, for example, have thrived by utilizing the infrastructure of the city, such as burrowing under sidewalks and foundations, which mimic their natural rocky habitats. Their status in Arizona is secure, reflecting their successful adaptation to living alongside the human population.