Critter Proofing Your Home

Critter Proofing Your Home

Be proactive

Start each year with a physical examination of your home, checking for potential problem areas such as small holes through which animals can gain access to your attic or a chimney cap that needs replacing. Conduct this survey and make all repairs early before pregnant females begin looking for sites in which to have their young.

Bird nest in attic louver

Check nest for babies. If present, check weekly until vacated, which will usually be 2–3 weeks. Once vacant, clean out the debris and screen the entire vent with ½ -inch mesh hardware cloth.

Squirrels or raccoons in attic

Check attic for babies, particularly in the spring and early summer. If present, allow them to grow big enough to leave the nest, which will be 6–7 weeks. If adults only are present, use mild harassment such as ammonia in open bowls, mothballs or loud music. Once the animals are gone, repair the entry point immediately.

Raccoons in chimney

Using a flashlight check the chimney for babies, particularly in the spring and early summer. If present allow them to grow big enough to leave, usually in 6–7 weeks. If you can hear them “chattering” in the chimney, they are probably already 2–3 weeks old. Do NOT set a fire in the fireplace; the babies cannot get out and will be burned. Adult raccoons will leave every night at dusk. Once all animals are gone, install a chimney cap.

Bird nest in dryer or stove exhaust vents

These are usually starlings. They raise young year-round but typically are active from early spring through early fall. When the young have vacated the nest, which will be in 2–3 weeks (and before the next clutch is laid), clean out debris. A vacuum cleaner hose is helpful. Cover vent opening with hardware cloth.

Bats entering attic

The only effective way to prevent bats from entering attics is to seal any gap greater than 1/2 inch and check the attic screening every winter. In addition to preventing bats from entering your attic, it helps you save money by saving energy. If bats are discovered, wait to exclude them until the young are able to fly, which will be by September 1st; otherwise desperate mothers will try to reunite with their young through any opening, meaning they are very likely to enter your living spaces. In addition, the young will starve to death and decompose in the attic, resulting in smells, stains and days of piteous crying.

Mice entering garage under door

Mice can enter ¼-inch gaps. Check doors for weather stripping. If chewed through, wrap metal flashing around bottom edge of door. Caulk and fill in any cracks around foundation of house. Do not use glue traps; they might catch a few mice but do not solve the underlying problem. They also catch other, innocent animals such as birds and bats.

Wildlife eating pet food

Do not feed pets outside, or if absolutely necessary, leave food out only during daylight hours. Pet food WILL attract wildlife.

Groundhogs burrowing under concrete slab, deck, porch, etc.

Do not attempt to evict groundhogs during winter months as they are true hibernators or during the spring to mid-summer when there are babies. At other times, use mild harassment techniques such as helium balloons tethered around the yard a few feet from the ground or a beach ball that will move with the wind around the yard. Groundhogs are cautious animals that are easily frightened. When you are sure the animal is gone, dig a trench along the slab 1 ½ feet wide and 1 ½ feet deep. Fold an appropriate length of 3-footwide hardware cloth into an “L” shape and bury in the trench. Tamp soil firmly and cover with a 1-inch layer of gravel, 6 inches wide and 6 inches deep.

Snake entering basement around duct or dryer vent

Caulk around all pipes, vents and ductwork that lead from outside to inside the house. Fill large gaps with steel wool before caulking.

General housekeeping

Keep shrubs and tree branches trimmed at least 1 foot away from the house or roof. Keep grass cut short. Check window screens for tears. Check attic vents for screens. Screen exhaust fans with hardware cloth. Check concrete patios and porches for signs of soil erosion away from the side and fill any gaps with 1-inch gravel if necessary.


  • Wildlife Rescue League Hotline Manual, 2003
  • Wild Neighbors, The Humane Approach to Living with Wildlife, by John Hadidian, 2007
  • Healers of the Wild, by Shannon Jacobs, 1998

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Wildlife Rescue League - Viriginia
Wildlife Helpline 703-440-0800
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