Tree Squirrels

Taxonomy

Domain	Eukarya
Kingdom	Animalia
Phylum	Chordata
Class	Mammalia
Subclass	Theria
Order	Rodentia
Suborder	Sciuromorpha
Family	Sciuridae
Subfamily	Sciurinae
Genus	Sciurus

Scientific Name

Sciurus niger

Common Name

fox squirrel

Compiled by Whitney Cranshaw, Colorado State University:

Fox Squirrel, Sciurus niger (L.)
Other arboreal mammals such as Pine (=“Red”) Squirrel, Tamiasciurus hudsonicus (Erxleben)
Abert's (= “Tassel-eared”) Squirrel Sciurus aberti Woodhouse
Chipmunk species, Eutamias spp.
Rock Squirrel, Citellus variegatus (Erxleben)
Golden-mantled Ground Squirrel, Citellus lateralis (Say)

Hosts

The fox squirrel debarks many species of deciduous trees, with elms, hackberry, honey locust, and Russian-olive being common hosts. Twig clipping follows a similar pattern. Both deciduous and coniferous fruits and cones are eaten, particularly oak acorns, walnuts, elm seeds, fruit-tree fruits, and honey locust pods, plus pine and spruce cones. The red squirrel strongly favors conifers in Colorado and mostly feeds on fleshy fungi and spruce and pine cones. The Abert's squirrel relies heavily on ponderosa pine for shelter and food. Rock squirrels spend a surprising amount of time in trees and occasionally feed on the bark of elms, Gambel oak and other trees. Chipmunks and the other ground squirrels spend most of their time on the ground but often can be seen feeding on various types of tree bark or fruits and cones.

Damage and Diagnosis

The feeding habits of these mammals, particularly the fox squirrel, are quite variable according to location, season and food availability. Squirrel damage to trees could be confused with that of insect in three cases: when they debark branches or trunks, clip twigs, or feed on fruits/cones. With debarking, incisor marks on the outer wood are characteristic. Squirrel clipped twigs littering the ground usually show missing parts, such as chewed buds. Squirrel damage to fruit and cones is usually indicated by teeth marks and the season in which it occurs (fall/winter). Prior to periods of brood-rearing (early spring and early summer), some fox and rock squirrels strip bark from Russian olive, honeysuckle and other live, woody plants for use as nest bedding.

The fox squirrel has a ten to 15-inch long body with a bushy tail about equally as long. Its body is rusty yellowish with a yellow to orange belly and a rusty brown tail. (For a description of the others, refer to a mammal book such as the Peterson Field Guide to the Mammals or Mammals of Colorado.)

Life History and Habits

The fox squirrel generally has two broods per year. They spend most of their time in trees, traveling between trees or burying food items gathered from trees. Being very opportunistic, their feeding is strongly tied to food available at the time. Thus, in spring they commonly feed on swelling flower and foliage buds. Later in spring, seeds and fresh foliage are commonly eaten. In summer all manner of food items are taken including insects, eggs, and plant parts including bark/phloem tissue. In fall, fruits and cones are heavily relied on. A common food item in early fall is hackberry nipplegall psyllid nymphs, taken by biting off the tops of the galls. In winter it is back to buds, bark and stored items from fall foraging activities.

Management

This can be a controversial issue. Squirrels are loved and even imported by some tree owners, despised by others. Live-trapping and relocation can be a lifelong operation, as new squirrels often fill in as fast as problem animals are removed. Seamless metal skirts can be wrapped around trunks to prevent squirrel access to tree crowns, provided the target trees do not have branches within jumping distance of adjacent trees.

With bird feeders often being a source of attraction to rodents, converting to squirrel-proof designs may be helpful (although “squirrel-proof” has proven to be an elusive concept). Squirrel-killed branches should be pruned to prevent human hazard and breeding by the smaller European elm bark beetle (insect vector of Dutch elm disease). Most squirrel damage is of a minor nuisance or cosmetic nature and should be tolerated.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.