Gray and Fox Squirrels

The gray squirrel (Sciurus carolinensis) and the fox squirrel (Sciurus niger) are members of the order Rodentia and family Sciuridae. Both are arboreal species that require mature forests for shelter and food. They spend the majority of their time in native hardwood trees such as oaks and hickories, and occasionally in pines.

 

They can be distinguished from one another by size and color characteristics. Size ranges from one to 1.5 pounds for adult gray squirrels and from 1.5 to 2.5 pounds for adult fox squirrels. Gray squirrels vary in length from17 to 20 inches and fox squirrels vary from 18 to 27 inches in length.

 

The gray squirrel varies in color from gray to brownish-gray with a noted for its characteristic salt and pepper coloration with yellowish to white underbelly and white tips on the tail hairs. The fox squirrel is orange pigments on its upper body parts, and pale yellow to orange underside and orange tips on the tail hairs.

 

 

Habitat Requirements

Gray and fox squirrels require mid- to late-succession forests, however, they will
forage in some early successional stages such as clearcuts, forest openings, or cropland. Both species can be found in bottomlands, on bluffs, and along rivers.

 

Suitable habitat must contain food sources through all seasons. Food is provided
by fruit- and nut-producing hardwoods, fungi, conifers, agricultural crops, and the
buds, flowers, and inner bark of some trees and shrubs. The most productive habitats have a variety of tree species.

 

Gray Squirrel

Gray squirrels are somewhat more restricted in distribution and habitat preference in Oklahoma than the fox squirrel. The gray squirrel is found only east of the 97th meridian in mature bottomland forests, hardwood uplands, forested ridges and oak-hickory-pine forests. Gray squirrels apparently prefer areas with denser understories than fox squirrels. In east-central Oklahoma, the gray squirrel will not be found in post oak-blackjack oak uplands or open pecan orchards, both of which are prime habitat for the fox squirrel. Gray squirrel habitat in Oklahoma is being lost because of the following: 1) continual conversion of bottomland forests to grasslands, croplands, and pecan orchards; 2) clearing of forests along tributary streams to make room for agricultural production; and 3) channeling of streams. Thus, the species distribution and abundance may continue to decline.

 

The gray squirrel requires a variety of trees and shrubs that provide adequate hard
mast (e.g., acorns and nuts), floral parts, buds, fruit (also called soft mast), cones, or
samaras as supplemental diet resources. An ample supply of potential den cavities must also be present for escape from predators, shelter from weather, and a place to rear their young.

 

Food

In fall and winter, the major food source for both squirrel species is hard mast such as pecans, acorns, and hickory nuts. The mast produced by heavy-seeded tree species
generally determine carrying capacity for squirrels in a given area. As a result, squirrel
populations often fluctuate with changes in hard mast yields.

 

In Oklahoma, hard mast trees often produce sporadically in a five- to seven-year cycle. During this cycle, there may be one excellent hard mast crop, one mast crop failure, and three to five years of poor to moderate mast production. Because of the periodic nature of mast crops, a variety of flora species must be present to provide alternate food sources and more stable habitat conditions. Important soft mast producing species include mulberry and blackberry. Maple, black gum, Osage orange, black cherry, and grape are also good food sources. Squirrels often ingest fruits, berries, bark, fungi,
roots, bulbs, floral parts, and in some cases animal parts (insects, other invertebrates,
etc.). A more inclusive list is shown in Table 1.

 

Squirrels consume an average of 1.5 pounds of mast (dry weight) per week. It takes
30 to 40 pounds of mast to sustain one squirrel through the breeding season. In the event of a hard mast failure, competition for food becomes intense and subadults will be forced from their home ranges by adults. This increases mortality in the subadult class, seriously affecting recruitment and population stability.

 

 

Table 1: Seasonal Food Preferences of Fox and Gray Squirrel

 

 

Water

Both fox and gray squirrels will readily drink free-standing water. Although available water is attractive to squirrels, it is not a limiting factor. Squirrels generally fulfill their daily water requirements from dew and succulent vegetation in their diet.

 

Cover

Den sites are preferred over leaf nests by both species for escape from predators and protection from weather, and for rearing their young. Preferred cavities are predominantly in 40 to 50 year old stands, have entrance holes two to four inches in diameter, are 12 to 20 inches deep, and are situated in the trunk or in a large limb of the tree. Limb cavities seem to be preferred over large hollow trees with large openings.

 

Radio tracking has shown that up to nine different shelters may be used on an annual basis by one animal. If there is a high population density, two to three all weather shelters should be available per squirrel per acre.

 

Fox squirrels are more likely than gray squirrels to use leaf nests in winter to raise their young. Leaf nests are usually built in trees with supporting grapevines. Fox squirrels need access to three or four trees with grapevines per acre, whereas grays need two or three.

 

 

Man-Made Squirrel Boxes

Nest structures can be made of wood, used rubber tires, or old ammunition boxes. Inner dimensions should be approximately 9.5 inches by seven inches by 18 inches. The entrance hole should be near three inches in diameter.

 

Gray Squirrels

Shelters should be situated 18 to 20 feet high in trees with no cavities or dens, arranged so that the entrance faces away from prevailing winds, and placed at a density of two to four per acre.

 

Fox Squirrels

Adult females tend to use shelters if they are anchored securely in the canopy of a tree with a limb above the structure, and close to a field edge. Subadults of both sexes and adult males are more likely to use them if they are placed below the canopy and away from the forest edge.

 

 

Home Range

Home ranges for fox and gray squirrels can span one to 20 acres. The overall shape of the minimum home range is non-circular and somewhat linear, with lengths up to four times greater than the width.

 

Gray Squirrels

Gray squirrel populations have definite social hierarchies with dominant individuals possessing and defending the largest home ranges. Males range further than females. In fall, subadults may disperse up to a mile to find a new home range.

 

Fox Squirrels

Fox squirrels tend to be less gregarious in nature than the gray squirrel. Generally, individual territories are not defended except near nest and den sites.

 

 

Intermediate Treatments

 

Thinning

Stand composition should reflect an array of tree species that will assure year-round food supplies. Oaks should comprise 50 percent of the tree species in key areas. Thinning should be done early and frequently to ensure rapid development of full crowns. Recognized den trees should be retained.

 

Prescribed Burning

 

Gray Squirrels

Generally, prescribed fire has limited but important application in gray squirrel habitat management. However, prescribed burning may be used to rejuvenate and improve production of decadent soft mast producers and sporadically to perpetuate den tree formation. Perhaps fire’s most important role in gray squirrel management is for site preparation for oak regeneration. Fire puts oak seedlings and saplings at a competitive advantage over less fire-tolerant species. Oaks also require mineral soil for germination, a condition created following some prescribed fires.

 

Fox Squirrels

Prescribed fire improves habitat conditions for the fox squirrel by reducing understory density. Winter burns may be conducted at three- to five-year intervals in pine types. If burns are more frequent than three-year intervals, understory fruit production may decline. Prescribed fire is an important tool in perpetuating a continual supply of den trees. As with the gray squirrel, fire is an important tool to manage for oak regeneration.

 

 

Direct Habitat Improvements

Full crown release of selected hard mast-producing species can improve mast production by reducing competition from surrounding trees for nutrients, light, and space. Mast production can be increased by nurturing mature trees with full crowns and by using selection cutting to encourage preferred mast production. Food and cover species may be planted but are of limited benefit compared to other practices. Nest boxes can be used but are not recommended on a large scale because of destruction caused by weather, vandalism, and the high cost of installation and maintenance. Road access within hardwood habitats should be minimized.

 

Other Species That Benefit From Squirrel Management

 

 

 

Manageent Options / SIP Cost-Share Opportunities

 

Low Intensity

Building of man made nest boxes (SIP-8; WH3)
Prescribed burning (SIP-8; PB3, PB4)

 

Medium Intensity

Building of man made nest boxes (SIP-8; WH3)
Planting of food and cover species (SIP-8; DH3, FP3, NG3, SL3, WA3)
Planting herbaceous and woody understory plants (SIP-8; UH3, US3)
Prescribed burning (SIP-8; PB3, PB4)

 

High Intensity

Building of man made nest boxes (SIP-8; WH3)
Planting of food and cover species (SIP-8; DH3, FP3, NG3, SL3, WA3)
Planting herbaceous and woody understory plants (SIP-8; UH3, US3)
Planting hardwoods (SIP-8; PT4)
Wildlife thinning (SIP-8; HT3, NT3)
Releasing mast trees (SIP-8; MR3)
Prescribed burning (SIP-8; PB3, PB4)

 

Acknowledgments: The following were used as a basis for some of the material
contained in this publication: Wild Mammals of North America, by J. A. Chapman and
G. A. Feldhamer, USFS Wildlife Habitat Management Handbook, Service Foresters Handbook, Stewardship Wildlife Notes from North Carolina Cooperative Extension Service, and Managing Forests to Maintain Populations of Gray and Fox Squirrels by C. M. Nixon and L. P. Hansen. When available or different, Oklahoma-based research information was used. Ecology of Fox and Gray Squirrels (Sciurus niger and Sciurus carolinensis) in Oklahoma by D. L. Chesemore (1975) was used extensively.

 

Lori Lowe Nicholson
Wildlife Extension Program Assistant

 

Dr. Ron Masters
Wildlife Specialist