WILDLIFE : Putting Out the Unwelcome Mat

You may find a mouse in the house, bats in your belfry, opossums in the garage or squirrels in the attic when wildlife seeks warmer creature comforts.

Uninvited wildlife is best managed with a policy of exclusion, conservationists say.

With exclusion, you find a way to discourage, or exclude, animals from your territory. It is a low-impact method of dealing with wild visitors that results in fewer injuries to the animals than trapping does and is much less likely to cause them undue stress.

Many people try live-trapping a marauder, transporting it several miles and then depositing it into a new environment. That method is not recommended, though, because the animal will not know where to find food and water in the new location and is often injured fighting with another adult as it tries to carve out a new territorial niche.

Conservationists urge people to block unwelcome animals from their homes and to remove obvious outdoor attractions such as a dish of pet food. Otherwise they advise leaving alone those that pose no threat.

Entry holes, once located, can usually be blocked with sheet metal, foam insulation or metal screening.

Finding the entry hole is not always easy. Some bats, for instance, can squeeze through an opening less than three-quarters of an inch in diameter. If these nocturnal creatures take up residence in your attic and you feel compelled to evict them, you can best determine their exit sites at dusk, when they generally leave their roost to feed.

Bats are much more benign than their reputation suggests. They consume hundreds of tons of destructive insects each year and help pollinate many plants.

Unlike squirrels and raccoons, one or two bats in a seldom-used attic will provide few clues that they are there. They don’t chew holes in your home or destroy insulation. Robert Benson, public information officer for Bat Conservation International, estimated that 80% of bats living in buildings and outbuildings go undetected.

Single bats that get into living quarters are most often misplaced youngsters. Open a window and close all doors--after the bat gets its bearings, it will generally fly out the window. This technique works with birds as well.

If the bat alights and you can get close, Benson suggested putting a coffee can over it. The bat will most likely crawl into it because it is a dark, safe place. Put on gloves, cover the end of the can with a piece of cardboard and carry it outside to release the bat.

If you have a whole colony in your attic, you probably want to exclude them. Find their entry point, wait until all the animals have vacated for the night, then hang a piece of bird netting over the outside of the hole.

Fasten the netting in place across the top and part way down the sides but leave the bottom open. This will allow the bats to fly out--they hit the net and drop down--but they won’t be able to re-enter.

Wait three or four days to make sure all the animals have vacated, then seal the hole.