Squirrels, members of the Rodentia family Sciuridae, are a highly diverse group of mammals recognized by their long tails and nimble movements. With over 270 species worldwide, their habitat spans nearly every continent and climate. This adaptability has allowed them to colonize ecosystems from dense tropical rainforests to arid desert scrublands.
The Three Major Types of Squirrels
The Sciuridae family is broadly categorized into three main lifestyle groups based on where they spend most of their time. The most commonly observed are tree squirrels, recognized by their long, bushy tails and sharp, curved claws that enable them to climb rapidly and descend trees headfirst.
Ground squirrels form the second category. These species are generally more robust than their tree-dwelling relatives, featuring shorter, sturdier forelimbs adapted for digging. This group includes well-known species like chipmunks, prairie dogs, and marmots, defined by their terrestrial and fossorial (burrowing) habits.
The third, least-seen group is the flying squirrels, unique for their patagium—a specialized membrane of furred skin that stretches from the wrist to the ankle. This membrane allows them to glide efficiently between trees, giving them an advantage in dense forest environments.
Global Distribution and Specific Habitats
Squirrels are one of the most widespread mammal families, found natively across the Americas, Eurasia, and Africa. Their presence spans a massive range of terrestrial regions, from northern boreal forests to equatorial rainforests.
Tree squirrels inhabit a vast array of forested environments, utilizing both deciduous and coniferous woodlands across temperate zones. The Eastern gray squirrel, for instance, has adapted well to urban parks and suburban areas in North America, thriving close to human development. Other arboreal species range from the boreal forests of Canada to the tropical rainforests of South America, and across the Old World, from northern Europe and Asia to the woodland savannas of Africa. They rely on the vertical structure of trees for safety, shelter, and access to food sources like nuts and seeds.
In contrast, ground squirrels are specialized for life in open, treeless ecosystems where they dig extensive tunnel systems. Their habitats include the open plains and prairies of North America, rocky slopes, and arid desert scrub. Certain species, like those found in the Arctic, have adapted to the tundra, spending a significant portion of the year underground in hibernation. The ability of ground squirrels to dig provides protection from predators and the harsh temperature extremes characteristic of these open landscapes.
Flying squirrels require mature forests with tall, dense tree cover to maximize the distance of their glides. These nocturnal animals live in the high canopy, launching themselves from one tree and using their patagium to reach another trunk over distances that can exceed 150 feet. This reliance on older, established forests makes them less common in fragmented or newly developed areas compared to their more adaptable tree squirrel cousins.
Physical Homes Dreys Burrows and Cavities
A squirrel’s home is a micro-environment built for shelter, nesting, and protection from predators and weather. Tree squirrels construct a structure called a drey, which is a spherical nest of leaves, twigs, and shredded bark, typically built in the fork of a tree or close to the main trunk. These dreys are generally one to two feet in diameter and situated 20 to 40 feet above the ground, providing an enclosed space for resting and raising young year-round.
For better insulation during colder months, tree squirrels often seek out natural tree hollows or cavities, which offer superior protection from wind and water. These dens may be old woodpecker holes or natural fissures in the trunk, and the squirrel will line them with soft materials like moss, feathers, and grass. A single squirrel may maintain multiple dreys and cavities throughout its territory, using them interchangeably based on seasonal needs or disturbance.
Ground squirrels and their relatives construct complex networks of underground tunnels known as burrows. These subterranean homes are excavated using their strong forelimbs and serve as permanent residences for protection and reproduction. A typical burrow system features multiple entrances, which helps the squirrel escape predators, and includes a main nest chamber lined with insulating plant material. These burrows are also the sites where many ground squirrel species hibernate during the winter, sealing themselves off to survive prolonged periods of cold.