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BEASTS BEGONE! Excluding Animals

Before Excluding an Animal

The best way to avoid problems with animals in your home, school or office is to prevent them from entering in the first place. Raccoons, woodchucks, bats, mice, and snakes can do considerable damage once they find a way into your building. This section offers some options for animal-proofing or excluding animals from buildings. (Products mentioned throughout this section are provided as examples and do not constitute an endorsement on the part of the New York State IPM Program, Cornell Cooperative Extension, or Cornell University.)

Is it in or out?

Before closing animal entry sites in a building, be certain that animals will not be trapped inside. If you are uncertain whether an entry site is active, monitor it for at least two days. Placing newspaper in the hole, stapling cardboard over the hole, or placing duct tape over the hole works well. Animals that currently inhabit the building usually will need to be removed before proceeding with exclusion.

Time of year.

In winter, many animals (e.g., woodchucks, raccoons, chipmunks) are inactive for long periods. You may think that an entry hole is inactive only to be unpleasantly surprised in the spring or during a warm spell. Snow and ice also make it difficult to safely work on the outside of a building.

Watch for little ones!

During the spring and summer, the presence of young animals can complicate exclusion. Listen for sounds (such as high-pitched squealing or chirping) of the young in walls, fireplaces, etc. Another sign, if you can get close enough, are the teats of female mammals: they will usually appear enlarged and bare of hair when nursing. Although it is generally not illegal in New York State to remove young animals from buildings, special consideration should be given as to when and how it is done.

Keep it legal.

Building codes, fire codes, and other ordinances are important to keep in mind when deciding how to exclude animals. For example, many homemade chimney covers do not meet legal safety requirements.

Does it work?

The durability and effectiveness of a technique varies by species and situation. To illustrate, bats are generally not able to chew or claw their way through most exclusion materials. However, they are often persistent in finding small, over-looked holes. Raccoons and rodents, on the other hand, are capable of removing insufficient exclusion or opening new holes into a structure. Be sure your methods are appropriate to your situation.

How does it look?

Keeping aesthetics in mind, choose options that do not detract from the looks of the building. Efficacy, however, should not be sacrificed for attractiveness. Replacing damaged woodwork in a vulnerable location may look better without a metal covering but animals may quickly damage the wood again. Painting the metal can improve its appearance and keep the animals out.


General carpentry tools are sufficient for most exclusion projects. These include hammers, staple guns, screwdrivers, caulking guns, pliers, tin snips, safety goggles, etc. Some special tools are also helpful.

Power drills. Keep two drills available in case the battery runs low in one. Two drills can also speed up work if you keep different bits in each drill. For example, if you are drilling holes through sheet metal and then attaching the metal to the building with screws, one drill can be used to drill the holes while the second can be used to drive the screws.

Foam gun. Particularly useful in bat exclusion, a foam gun (such as the Todol® system) cleanly and quickly sprays expanding foam insulation into structural cavities and cracks.

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