Squirrels are a diverse group of mammals, often observed scampering and climbing with remarkable agility. While many people associate squirrels with their arboreal antics, not all squirrels can fly in the way birds or bats do. Only a specialized group, known as flying squirrels, possess a unique anatomical adaptation that allows them to glide through the air, a distinct form of locomotion from powered flight. This gliding enables them to travel efficiently between trees without the energy expenditure of climbing down and up.
The Gliding Masters
Flying squirrels utilize a specialized membrane called the patagium for their aerial movements. This membrane stretches from their wrists to their ankles, creating a wing-like surface. When a flying squirrel leaps from a high vantage point, it spreads its limbs to form a parachute-like structure. This generates lift and controls their glide trajectory.
The mechanics of their glide involve sophisticated control. Flying squirrels can steer and adjust their glide path by changing the positions of their limbs and body, using their long, flattened tail as a stabilizer and an airfoil. Cartilaginous extensions from their wrists help to support the patagium and allow for precise aerodynamic adjustments, even enabling turns of up to 90 degrees in mid-air. These animals are primarily nocturnal, using their large eyes for excellent vision in low-light conditions. Their omnivorous diet includes a variety of foods such as seeds, nuts, fungi, fruits, insects, and occasionally bird eggs.
Ground and Tree Dwellers
In contrast to gliding squirrels, most squirrel species are either tree dwellers or ground dwellers, lacking the patagium. Tree squirrels, such as grey and red squirrels, are adept climbers and jumpers. They possess strong claws for gripping bark and highly flexible ankle joints that allow them to rotate their hind feet 180 degrees, enabling them to descend trees head-first. Their bushy tails are crucial for balance during acrobatic maneuvers and quick turns between branches.
Ground squirrels, which include chipmunks and prairie dogs, primarily inhabit burrows and open grassy areas. These squirrels are built for terrestrial movement, relying on running and burrowing for foraging and predator evasion. Their diets are varied, including nuts, seeds, fruits, insects, and sometimes small vertebrates or carrion. Unlike flying squirrels, many tree and ground squirrels are diurnal.
Key Differences and Shared Traits
The primary distinction between flying squirrels and their non-gliding relatives is the patagium. This specialized membrane allows flying squirrels to glide, a movement not possible for tree or ground squirrels. Flying squirrels are also nocturnal, with larger eyes adapted for low-light conditions, while many other squirrel species are diurnal. Their mode of locomotion differs significantly, with flying squirrels relying on controlled descents and non-gliding squirrels utilizing climbing, running, and jumping.
Despite these differences, all squirrels share fundamental characteristics as rodents. They possess continuously growing incisors, which they must gnaw on to maintain a functional length. Most squirrels also have a bushy tail, which serves various functions including balance, communication, and thermoregulation. Their diets include a mix of plant matter, such as nuts, seeds, and fruits, and sometimes insects or other small animal matter.