Trees are fundamental to the lives of squirrels, providing resources necessary for their survival and well-being. These arboreal mammals rely on trees for a diverse range of purposes, from sustenance to sanctuary.
Trees for Food Sources
Trees serve as a primary food source for squirrels, offering a rich variety of nuts, seeds, buds, and sap throughout the year. Squirrels exhibit distinct preferences for certain tree species due to the nutritional content and accessibility of their provisions.
Oak trees are important, providing acorns that are a staple in a squirrel’s diet, especially in autumn and winter. Acorns contain amounts of protein, carbohydrates, fats, and minerals such as calcium, phosphorus, and potassium. Squirrels often prefer white oak acorns, which have a lower tannin content and a less bitter taste, consumed immediately upon discovery. Red oak acorns, with their higher tannin levels, are frequently cached for later consumption, allowing tannins to leach out.
Hickory and walnut trees are also favored for their energy-rich nuts. Hickory nuts are beneficial, offering a high fat content, sometimes exceeding 80%, which provides energy for squirrels. Walnuts are rich in healthy fats, proteins, vitamins, and minerals, making them a good energy source. The hard shells of these nuts also help squirrels maintain healthy teeth, as gnawing wears down their continuously growing incisors. Pecans, similar in nutritional profile to hickory nuts, are another popular choice.
Beyond nuts, squirrels consume seeds from various trees, including maple, pine, and elm; maple seeds, often called “helicopters,” are a popular food source, particularly in spring. Pine cones provide seeds that are a food source for red squirrels. In times of scarcity, in late winter and early spring, squirrels consume tree buds and even sap. They target swelling flower buds from trees like elm and maple, which offer nutrition before leaves emerge. Squirrels also tap into the sap of trees, especially sugar maples and black birches, by biting into the bark to access the sugary liquid, which provides sugars and minerals.
Trees for Shelter and Nesting
Trees provide squirrels with shelter from predators and weather, serving as locations for both dens and nests. The structural characteristics of different tree species determine their suitability for these protective purposes. Squirrels utilize natural tree cavities or construct elaborate nests, known as dreys, depending on availability and environmental needs.
Natural tree cavities, often found in older or larger trees, offer secure dens. These cavities can be pre-existing holes, perhaps created by woodpeckers, which squirrels then claim and adapt. These dens provide protection from rain, wind, and snow, making them preferred for winter lodging and raising young. Trees such as oak, hickory, and maple are frequently used for these cavity dens due to their size and propensity for forming hollows.
When natural cavities are unavailable, squirrels construct dreys, which are spherical nests typically built in the forks of branches or close to the tree trunk, usually at least 6 meters (20 ft) above the ground, with flying squirrels building even higher. They are constructed from an outer layer of twigs, leaves, and grass, woven into a ball-like shape, often around 30 centimeters (12 inches) in diameter. The inner lining of a drey consists of softer materials such as moss, shredded bark, leaves, and pine needles, providing insulation. Different tree species, including beech, elm, and oak, provide suitable materials for drey construction. While dreys offer shelter year-round, squirrels may build multiple nests and often prefer more protected cavities during colder months.
Trees for Movement and Safety
Trees are essential for squirrel movement, enabling efficient foraging, escaping predators, and social interactions within their habitat. The physical attributes of trees, such as bark texture, branch structure, and canopy connectivity, directly support these behaviors. Squirrels possess specialized adaptations that allow them to navigate their arboreal environment with agility.
Trees with rough bark provide good grip for squirrels as they ascend and descend trunks. Their sharp claws dig into the bark, providing a firm hold on both vertical and horizontal surfaces. This grip, combined with powerful hind legs, allows them to scale trees quickly. Squirrels can even descend trees headfirst, a unique ability enabled by their rotating ankle joints, which allow their hind feet to face backward and grip the bark from the opposite direction.
Interconnected canopies are important for movement, allowing squirrels to move between trees without descending to the ground. They use wide branches as “highways” for efficient movement. The flexibility of their limbs and joints enables a wide range of motion, essential for maneuvering through complex branch networks and making precise leaps. Their bushy tails act as balancing aids, maintaining stability on narrow branches and providing direction during jumps.
Trees also offer vantage points, allowing squirrels to survey their surroundings for food and threats. By moving strategically through the canopy, squirrels can evade predators. The density of branches and foliage provides cover, enhancing safety. This combination of structural features and specialized adaptations makes trees essential for a squirrel’s active and safe lifestyle.