Introduction
The eastern gray squirrel (Sciurus carolinensis) is a common sight across the eastern United States and beyond. Recognizable by its bushy tail and grayish fur, this adaptable rodent plays a significant role in its environment. Understanding its diet is key to appreciating its ecological impact and managing its interactions with humans. This article delves into the intricate details of the eastern gray squirrel's diet, exploring its preferred foods, seasonal variations, and the occasional deviations driven by scarcity.
Description and Range
The eastern gray squirrel is a bushy-tailed rodent with a mixture of brown, black, and white fur, which, when viewed from a distance, blend together to look gray. Their belly fur is white or light gray. The tail is flattened, bushy, and gray with silvery-tipped hairs. Some gray squirrels may be black, white, or blond in color. These color morphs can be common in some locales. Gray squirrels are typically 16-20 inches in length and can weigh up to 1.5 pounds.
Gray squirrels can be found throughout the eastern United States, ranging from southern Quebec, New Brunswick, and Ontario to Florida, west into eastern Texas, and north into southern Manitoba. This species has also been introduced to many locations outside of its native range, including Washington and British Columbia. Eastern gray squirrels can be found in every county in Maryland.
Habitat and Behavior
Gray squirrels generally are found in mixed hardwood forests as well as suburban and urban areas. The trees most commonly used by gray squirrels are white oak, American beech, American elm, red maple, and sweet gum. The eastern gray squirrel is most active during the day and can be seen all year, even digging through snow in intense cold to retrieve buried nuts. The squirrels can make hundreds of caches. Most nuts are buried at the surface, with few more than 1/4 inch below the ground. About 85% of the nuts may be recovered, while the remainder occasionally germinates. The gray squirrel can smell buried nuts under a foot of snow; when snow is deep, the squirrel tunnels under it to get closer to the scent.
Primary Food Sources: Nuts, Seeds, and Berries
The gray squirrel's diet primarily consists of nuts, seeds, and berries. Acorns, hickory nuts, walnuts, beechnuts, and pine seeds form the cornerstone of their food supply. These items are rich in fats and proteins, providing the energy needed for survival, especially during the colder months.
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- Acorns: A staple food, particularly from oak trees.
- Hickory Nuts: Another favored nut source, offering high nutritional value.
- Walnuts: Consumed when available, adding variety to their diet.
- Beechnuts: A smaller nut that can be an important food source in certain regions.
- Pine Seeds: Especially important in areas with abundant pine trees.
In addition to nuts, gray squirrels consume a variety of seeds and berries. Maple samaras (the winged seeds of maple trees), wild grapes, and American holly berries are among the many options they exploit.
Seasonal Dietary Variations
The diet of the eastern gray squirrel is not static; it changes with the seasons, reflecting the availability of different food sources.
Spring
In the spring, as nuts and seeds stored from the previous fall become scarce, gray squirrels turn to alternative food sources. Buds of maple, tulip poplar, flowering dogwood, and black cherry become important at this time. These buds provide essential nutrients as the squirrels prepare for the breeding season.
Summer
During the summer months, the diet expands to include a wider variety of fruits, berries, and other vegetation. Availability of these items ensures a balanced intake of vitamins and minerals.
Autumn
Autumn is a critical period for gray squirrels. It is during this time that they gather and store nuts and seeds to sustain them through the winter. This behavior, known as caching, involves burying food in numerous locations throughout their territory.
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Winter
In winter, the gray squirrel relies heavily on the nuts and seeds they cached in the fall. Their ability to locate these buried food stores, even under a blanket of snow, is crucial for their survival.
Opportunistic Feeding Habits
While primarily herbivorous, eastern gray squirrels are opportunistic feeders and will occasionally consume non-plant-based foods. When their typical food sources are scarce, they may supplement their diet with insects (adults and larvae), juvenile birds, bird eggs, and amphibians. This adaptability allows them to survive in environments where food availability may fluctuate.
The Role of Gray Squirrels in Seed Dispersal
Eastern gray squirrels play an important role in what’s known as seed dispersal. As winter approaches, squirrels carry their food and bury it in several locations, but they sometimes forget exactly where. That helps the environment because these buried seeds and nuts sprout and grow the following spring. Their habit of burying nuts and seeds contributes significantly to forest regeneration.
Communication and Sensory Abilities
Eastern gray squirrels have an excellent sense of smell, which they use to help locate food that they’ve hidden away. They can also pick up information about their fellow squirrels by smelling them. They communicate with each other by making sounds and body movements, such as tail flicking. When predators such as red foxes and red-tailed hawks are nearby, eastern gray squirrels will sound warning calls to alert other squirrels.
Gray squirrels are quite vocal. The most familiar sound they make is a bark. Buzzing, wailing, squealing, trills, squeaks, and purrs are other common squirrel sounds. Squirrels use their tails for balance and for communication.
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Habitat and Den Use
Gray squirrels generally are found in mixed hardwood forests as well as suburban and urban areas. The trees most commonly used by gray squirrels are white oak, American beech, American elm, red maple, and sweet gum. Gray squirrels will use old woodpecker holes or natural tree cavities as dens to live in and raise young. Eastern gray squirrels will also build large nests composed of leaves and twigs. Generally, dens are made at least 20 feet off the ground. Gray squirrels are often social and will share their nests with other gray squirrels during certain times of the year.
Den trees are essential to squirrels for winter shelter, escape cover from predators, and rearing of young. Natural den cavities begin to appear in 40-50 year old stands. Although leaf nests are also used, the survival rate of young is 40% lower in leaf nests compared to cavities. Frequently, squirrels will claim 2 or 3 dens at the same time. Moderate to dense cover, including midstory and canopy trees, is preferred for concealment from aerial predators such as hawks and owls. Dense tree cover also allows gray squirrels to move freely through the canopy. On average, about half of the den cavities identifiable from the ground are suitable for raising young.
Reproduction and Life Cycle
Eastern gray squirrels males reach breeding age at 9-11 months and females are about to breed around 6-8 months of age. After that, the eastern gray squirrel mates twice a year from December to February and from May to June. A mating "chase" is often involved, with several males following a female as she moves about during the day. Gray squirrels are polygamous, with one male mating with several females. After mating, gestation takes around 40-45 days. Eastern gray squirrel litters range from 2-6 young that are born hairless and helpless. Frequently, the spring litter of young is born in a tree cavity, while the second, late-summer litter is born in a leaf nest. Females often move their litters back and forth between cavity dens and leaf nests, generally to escape predation or parasite infestation as well as due to weather changes. The young are weaned in about 50 days. Typically, gray squirrels have 2 litters per year. The second litter stays with the female over the winter.
Female eastern gray squirrels may start having babies at as young as five and a half months old. Females can have litters twice a year, each usually consisting of two to four babies. They gather leaves and twigs and build nests high in the trees to house their young offspring, or use tree cavities as dens.
Newborn eastern gray squirrels don’t have fur when they are born and are not able to see. They often weigh as little as half an ounce (14 grams).
Mortality is high in young gray squirrels. A nestling gray squirrel has a 25 percent chance of surviving its first year. Survival increases to 50 percent once they are around one year old. In the fall, about half of the population is composed of young squirrels.
Management and Conservation
Gray squirrels are managed as small game species in Maryland and North Carolina. Squirrel populations fluctuate with changing yields of hard mast, especially acorns. When mast is not available, squirrels will eat other fruits and berries, flower parts, buds, bark, roots, mushrooms, and animal matter. Variety in tree species is essential for habitat stability.
Numerous game and nongame species with habitat requirements similar to squirrels benefit from squirrel management. Rather than focusing on a single species, habitat management plans should emphasize the communities of which squirrels are a part.
Conflicts and Solutions
Squirrels are often abundant in many urban and suburban areas and are comfortable living near humans. Conflicts can occur when squirrels feed on garden or nut crops, move into occupied dwellings or chew on structures. The most effective way to reduce squirrel damage is by modifying the habitat. Pruning tree branches near homes can prevent squirrels from accessing and entering dwellings. Metal flashing around tree trunks can prevent depredation of fruit and nut trees if the canopies of surrounding trees are not within jumping distance of a squirrel.