Squirrels |
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History and Biology: Tree squirrels are well known animals commonly seen scampering about in forests and parks. There are several species of tree squirrels in the United States . The most commonly encountered tree squirrels are the gray squirrel (Sciurus carolinensis) , the red squirrel (Tamiasciurus hudsonicus) , the flying squirrel (Glaucomys spp.) , and the fox squirrel (Sciurus niger ) . One or more of the species of tree squirrels are found throughout the United States . Because of their aesthetic value and importance as a game animal, the Sciurus species of tree squirrels have been deliberately introduced into areas where they did not occur previously. They prefer wooded areas and build their nests in trees. However, they frequently invade the attics and garages of houses for shelter, nesting, and to store food. They can become troublesome around structures by gnawing on exterior and interior walls, shingles, timbers, insulation, and electrical wiring. They may be very noisy in their activities such as running and chattering over roofs and through attics and walls. The flying squirrel is nocturnal while all other tree squirrels are diurnal. They all feed on a variety of materials such as fruit, bark, leaves, fungi, insects, bird eggs, small mammals, nuts, acorns, pecans, buds, bulbs, and young shoots. Their feeding activity can damage trees, gardens, and ornamental plants. They do not hibernate but tend to store large quantities of food in excess of that needed to survive the winter. Tree squirrels build nests in tree hollows and in the limbs of trees. Flying squirrels nearly always build in hollows. Nests are made of leaves, twigs, and bark. Tree squirrels have 2 to 7 young per litter and 1 or 2 litters per year, one early spring and one late summer. Flying squirrels usually only have one litter per year. Public Health Damage: Tree squirrels may bite when cornered. They have been observed to be aggressive in parks when being fed by people, to the point that they sometimes bite the hand that feeds them. The red squirrel and the flying squirrel have been implicated in zoonotic diseases, but direct disease transmission is rare. Tree squirrels are not regarded as significant vectors of human disease. However, plague has been isolated from the flying squirrel in Nevada . Relapsing fever has been transmitted to humans by contact with a red squirrel. Colorado tick-fever and antibodies to Powassan virus have also been found in the red squirrel. Tree squirrels also harbor a number of ectoparasites such as, fleas, ticks, mites, and chiggers. When tree squirrels nest in attics and other parts of human structures, their ectoparasites may become troublesome for humans. Structural Damage: Tree squirrels can become troublesome around structures by gnawing on exterior and interior walls, shingles, timbers, insulation, and electrical wiring. They may cause shorts in power transformers during their activities around power lines. Agricultural Damage: Although rare and not considered significant, tree squirrels may threaten the health of humans and livestock in the United States because they may be a reservoir for potentially transmittable disease to both humans and livestock such as, plague, relapsing fever, and Colorado tick-fever. Additionally, they do damage through the consumption and contamination of agricultural seed, nut, fruit, and grain products in the field, storage facilities, and wholesale and retail outlets. Environmental Damage: Because of its commensal relationship with humans and its potential for inquisitive investigations into structures and food supplies, the tree squirrel is a constant public health and property damage problem. In nature, tree squirrels feed on small mammals, birds, eggs, trees, plants, and bulbs and may have a negative impact on the population richness and densities of native songbird, small mammal, and plant species. Economic Damage: Economic damage from the tree squirrel is difficult to assess when you consider the intangible costs of the impact of zoonotic diseases on the public health of humans, livestock, domestic animals, and wildlife. Additionally, it is also difficult to determine the real cost of equipment and structural damages from chewing, gnawing, and nesting. Also, there is a significant cost to American consumers and business from the consumption and contamination of seed, grain, fruits, nuts, and vegetables damaged by tree squirrels. It is difficult to evaluate the damage to populations of native songbirds and small mammal species. References: Mallis, A. 1997. Handbook of Pest Control: The behavior, Life History, and Control of Household Pests, Eighth Edition. Mallis Handbook and Technical Training Company. Bennett, G. W., Owens, J. M., and Corrigan, R. M., 1988, Truman's Scientific Guide To Pest Control Operators, Harcourt Brace Jovanovich, Inc., One East First St. , Duluth , MN . 55802 |
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