[Mallis Excerpt] Movin' In

As more homes are built in wooded areas and surrounding semi-rural communities merge with cities to become suburbs, people are increasingly coming into conflict with wildlife. Animals that previously were "in the country" are now regular backyard visitors. Urban wildlife management is currently one of the fastest-growing segments of the pest control industry. Services to control wildlife, however, require special training and experience and are not for every pest control company. Regulatory concerns can be a major issue in dealing with wildlife as many of these animals may be protected under local, state and federal statutes. Permits are often needed to trap many of the animals discussed in this story.

Structural pest management professionals are frequently called upon to resolve pest or nuisance problems involving a wide range of vertebrates. Vertebrate pests and nuisance wildlife can be defined as any vertebrates, native or introduced, domestic or feral, that adversely affect human health or well-being or conflict in some significant way with human activity or interests. A particular species may be a pest in one situation but in other circumstances be considered desirable or beneficial. Hence, the categorization of certain vertebrates as pests is done primarily to define a situation or as a reference from which to resolve a particular biological or ecological problem. Social, cultural and political factors often play significant roles in the strategy and methodology of resolving some pest management problems associated with these animals.

Numerous laws and regulations govern how, when, where or why you can manage or control vertebrate species. They may occur in many different codes or bodies of law and reflect federal, state, county or city authority. Some are restrictive and deny control options; others are mandatory and compel actions that will resolve the pest problem. An example of the latter is the Food and Drug Administration’s enforcement of laws and regulations concerning bird contamination of food. Laws and regulations governing pesticide registrations and their use are extensive and sometimes complex and pesticide regulations change constantly and special effort is required to remain abreast of the current statutes.

Where feasible, most pest problems are best resolved through prevention. Animal-proofing of buildings or the use of other exclusion methods is paramount for preventing damage from pests, such as tree squirrels, bats and pigeons. Sanitation and methods for modifying or manipulating habitats to reduce food and/or water availability or harborage of the unwanted species are of significant importance and represent a major component of integrated pest management. Even before this management term was adopted, IPM approaches played a vital role in vertebrate pest management and control because total dependence on chemical control or other single-method strategies have never been possible with many pest animal problems. Concurrent and multiple techniques and methodologies are commonly used in preventive and animal suppression management strategies of vertebrate pests in a wide array of settings.

SQUIRRELS. Tree squirrels and flying squirrels can cause damage or become a nuisance to the homeowner when they use buildings for nesting sites and food storage or when they gnaw into attics to take up residence. They also may move into spaces between walls and floors. Squirrels often gain access through vents, broken windows, knotholes and construction gaps under eaves and gables. Occasionally, the chimney and fireplace provide an entry route.

Squirrels have a remarkable ability to destroy wooden shakes and shingles, with cedar seeming to be a favored wood. The amount of structural damage may at times be severe. They can be particularly destructive to summer or vacation cabins left vacant during part of the year, as they are free to continue their activities until the owner returns. Garages, barns, stables, tool sheds and other buildings often serve as homes for tree squirrels.

Rarely do tree squirrels take up residence inside an occupied building without being seen or heard at once. A possible exception is flying squirrels, whose presence in an area may be unsuspected because they are only active at night. The typical evidence of tree squirrels includes droppings, gnawed holes, nest materials, food stores, shells, nut hulls, pits and other food remnants. If squirrels are in the attic or garage, the occupant will likely hear them moving about, even if the animals are unseen.

In backyards and landscaped areas, squirrels will dig up vegetable and flower gardens, primarily for seeds and bulbs. Seasonally, they will clip flower buds and leaves and often strip the bark from trees and various ornamental plants. They are particularly fond of maturing nuts and fruit; and where only a few trees exist in a backyard, they can literally strip them of a crop of walnuts, almonds, pecans, etc. Tree squirrels are fond of burying food items, such as acorns and nuts, and their diggings can be destructive to turf and other landscaped areas.

Utility companies report that tree squirrels often cause loss of electrical and telephone service by gnawing into cables and stripping insulation. This damage causes shorting, sometimes resulting in fires or grounding and can be difficult and costly to repair. Power outages cause significant economic losses. Special cables with protective metal sheaths that cannot be gnawed through are available but they are considerably more costly than standard cables. Overhead power and communication lines are frequently used by tree squirrels to travel from one site to another. Rodent fleas, ticks and mites are common ectoparasites of tree squirrels. When squirrels take up residence in dwellings, their ectoparasites may prove troublesome to humans.

CONTROLLING SQUIRRELS. Tree squirrels can be a challenging pest to control. Options pest management professionals should consider include:

Pruning. Tree branches should be pruned at least 6 feet from all building surfaces. The removal of tree limbs that overhang the roof will sometimes eliminate access by squirrels. (Any distance of 6 feet or less can be considered an easy jump for most tree squirrels.)

Refraining From Feeding. Feeding squirrels and coaxing them to approach dwellings and people is a sure way to encourage nesting in nearby trees or the dwelling itself, if accessible. Those who have squirrels invading or damaging structures should be admonished to refrain from feeding squirrels close to occupied buildings. Likewise, squirrels that routinely gain access to backyard or window bird feeders can be discouraged from continuing their raids as a result of installing squirrel excluder devices on bird feeder poles and brackets, if done correctly.

Exclusion. Exclusion (rodent-proofing) is the best and most permanent solution to squirrels gaining access to dwellings. Sheet metal or wire hardware cloth is most often used to close openings. It is important when closing all possible entry routes not to trap animals inside. Therefore, a thorough trapping effort must precede any exclusion procedure in order to achieve lasting results.

Squirrels may be prevented from climbing trees by attaching a wide metal band or collar around the trunk at least 6 feet from the ground. Aluminum roof flashing, fitted snugly, works well but must allow for growth to prevent damage to the trees. These collars should be about 18 to 20 inches wide with no gaps or rough surfaces to permit climbing. Collars are useless if tree limbs are within jumping distance of the ground, nearby trees, fences or other structures accessible to squirrels.

Live-Trapping. If the population of tree squirrels must be reduced, trapping is most often the method of choice. Live-catch 24- by 8- by 7-inch and 16- by 5- by 5-inch or similar-size wire cage traps are effective. If squirrels are entering the premises via overhead routes, such as trees or power lines, trap placement on roof-tops at gutter level or secured to tree limbs may be the most appropriate settings. For best results in dealing with trap-shy squirrels, traps should be prebaited for several days with the doors secured in the open position; when the bait is readily taken, the traps can be rebaited and set. A wide variety of baits may be acceptable: peanuts, walnuts, pecans, acorns, sunflower seeds and raisins have all been effective. Live-catch traps should always be checked at least once daily to remove squirrels or to release other animals accidentally captured.

Lethal-Trapping. Where legal, smaller tree squirrels can be killed with ordinary wood snap traps used for rats. The same baits suggested for live traps can be used. All baits should be tied to the trigger with thread or light string; otherwise, some squirrels will become proficient at stealing baits without being caught. These traps can be nailed or fastened to fences, tree limbs and rooftops to increase trap effectiveness. In outdoor situations, unless snap traps are placed with considerable foresight, they will occasionally catch birds. An exception to this would be the use of snap traps in attics or other indoor locations frequented by tree squirrels. If traps are set on a flat surface in a building, a strong string or light wire should be used to secure them to heavy or fixed objects to prevent them from being dragged away. Like cage-type traps, kill traps should be placed in position and baited for several days before setting.

Modified box-type pocket gopher traps are also effective kill traps for tree squirrels when baited with nuts. Body-grip kill traps or tunnel-type lethal traps can give excellent results, but care must be taken to avoid capturing non-target species.

Repellents. Non-toxic sticky repellents (e.g., polybutene) may be helpful in discouraging tree squirrels from walking or climbing on some surfaces. At least one tacky repellent is currently registered for tree squirrels.

Toxic Baiting. No EPA-registered rodenticides are available for tree squirrel control and the poisoning of tree squirrels is not permissible in many states. Before even considering this approach, it is important to check with wildlife or conservation officials. Tree squirrels are susceptible to most of the same rodenticides used for Norway and roof rat control.

Editor’s note: This story was excerpted from the upcoming ninth edition of the Mallis Handbook of Pest Control. For more information visit www.mallishandbook.com.

The author is vice president and technical director of Varment Guard Environmental Services, Columbus, Ohio. He can be reached at gwegner@pctonline.com.