By John Hadidian, Ph.D.

The idea of using exclusion techniques or devices to keep wild animals out of places where they come into conflict with humans has been around for a long, long time. The Roman historian Josephus described structures placed on rooftops in Jerusalem to keep birds—possibly storks, who could have caused structural damage from the heavy nests they build—from roosting on the roofs. A much more contemporary application of exclusion technology can be seen by taking a look at the chimney on your house. It should be topped with a stainless steel cap both to keep weather out and to prevent unwanted visitors—usually birds, raccoons, and squirrels—from finding their way down the flue. Like all conflict resolution strategies, however, there can be drawbacks, particularly with birds such as chimney swifts.

In general, though, the merits of exclusion far exceed any harm caused by its unintended effects. Exclusion is a proactive, humane, and enduring way to avoid conflicts with wildlife. If a conflict already has occurred, exclusion is also the most promising way of resolving it. Exclusion tactics can be applied to species as small as a mouse or as large as a moose and to situations as varied as individual homes to the expanse of the open range. We could write a book about it and, in fact, we have—Wild Neighbors: The Humane Approach to Living with Wildlife. For this discussion, however, we'll keep to a few basic principles and focus on typical situations you might encounter around your home.

A Proactive Approach

Excluding wild animals from our homes and property can be viewed in a hierarchical fashion. First, problems are addressed before they occur, and then the level of involvement is gradually raised to the point where the animals are evicted before permanent exclusion can take place. For example, through a little judicious housekeeping, potential problems with the wild animals who move into or under our houses can be headed off before they occur. Homeowners should constantly be aware of wildlife activity in and around their homes, not only because of the enjoyment this can bring, but also to intercept any potential problems before they happen. At a minimum, try to conduct a biannual survey of your home and property. Look for signs of wildlife activity, and examine the condition of your home, sheds, and outbuildings.

What to Look For

People often don't look up to see what's going on above their heads, and it's a good idea for every homeowner to do that once in a while. Look for loose siding, deterioration of boards along the roof line, and loss of integrity in the screening used behind attic louvers. An often overlooked portal into the house can occur where electrical lines or air conditioning conduits enter the building. These are usually sealed with a putty material that can deteriorate, or it may not be replaced after repair work has been done. Once that happens, any passing mouse may be powerfully tempted to explore the welcoming hole into the curious new world of a basement. Fast on the scent trail of the mouse, there may be a snake, and it is usually when one or both of these creatures are discovered inside a house that domestic harmony begins to deteriorate. While window wells don't provide access into a building, animals do sometimes get trapped in them while exploring.

Looking down can help too, since a lot of activity can take place at ground level or below. Areas under decks and along foundations are common sites of animal activity. Skunks often find the area under a deck very inviting, and sometimes even a fox will utilize such places. Chipmunks will burrow near or along foundations.

Taking Appropriate Action

So what are we to do when we actually discover a wild creature inside our house? Usually technology comes to the rescue, but we must proceed with caution. We need to take particular care in determining when to employ an exclusion strategy, because one of the most common reasons wild animals invade our homes is to seek secure places to give birth and raise their offspring. It is absolutely critical in any exclusion effort to remember there may be dependent young present. Beyond that, there simply are times during the year when exclusion could be inhumane, given conditions outside and the availability of adequate shelter.

That said, there are some fairly simple solutions for the homeowner who wants to head off problems before they occur, or to fix the conditions that contributed to an existing conflict so that it doesn't happen again. For example, take a skunk in the window well. Assuming you've encountered this particular situation and want to avoid a repeat experience, we recommend that you consider purchasing one of the clear plastic shields that are made to cover these areas. For a few dollars, these shields provide perfect exclusion capabilities, as well as insulation. If you need to lure a skunk out of your window well, it is useful to know that skunks can and will climb a rough board if the ascent is not too steep, and they can always be coaxed into a carrier, such as a large plastic wastebasket baited with a little cheese (the smellier the better), usually with no trauma to all concerned parties.

The area under a deck can be secured from wildlife use by installing garden fencing (such as one-inch by two-inch metal cloth, sold in rolls). To be effective, you will need to bend it so that you create an apron of fence material that projects in front of the vertical fence, forming an "L" that prevents an animal from digging under it.

Work above ground can be more complicated if dependent young are present and may require professional expertise. Generally, the invasion of an attic by squirrels or raccoons merits professional intervention or carefully planned work done by the homeowner. You will need to ensure that young are not present, develop an appropriate and humane strategy if they are, and make certain that human safety is taken into account through exercising extreme care on ladders and in places when a misstep could mean injury.

Exclusion is one of the most humane and appropriate responses we can take when conflicts with wildlife occur in or around our homes or buildings. While the concept of exclusion is fairly simple, the exact type necessary in any given situation depends on many variables. Does this mean that homeowners cannot perform their own exclusion work? Of course not. It just means that, to be effective, homeowners need to be armed with the right information so that they will be able to choose the right approach for their particular circumstances.

John Hadidian is director of The HSUS Urban Wildlife Program