Preventing Problems

Handbook Contents | Best Practices Learning Objectives | Assess the Situation | Choose Management Options | Tools and Techniques | Preventing Problems | Evaluating Success | Resources | ICWDM | Wildlife Species Information


Best Practices: A step-by-step guide

Step four: Prevent future problems

Most nuisance wildlife control work is in response to a problem that has already happened. Is there a way to turn that around, to actually prevent problems? Or at least, to prevent them from happening over and over and over again? Absolutely, and this is emerging as a more important part of nuisance wildlife control.

There are two major approaches to preventing wildlife conflicts: habitat modification and exclusion. We’ll also discuss one strategy that’s common in agricultural pest management, which we believe may become an important service offered by some NWCOs: monitoring.

Prevent future problems: Habitat modification

Animals look for food, water, and shelter. When practical, modifying the environment to reduce the amount of available food, water, or shelter will make the site less attractive to an animal.

For additional wildlife control information on various species visit the Wildlife Species Information link. Each account describes some of the basic biology you need to know to work with this species, and then lists control techniques for that animal.

The following two lists offer some general tips for modifying the habitat to make it less vulnerable to wildlife damage.

  • Remove artificial food sources. If anyone is feeding the nuisance animals, persuade them to stop. It may even be illegal. Why? Because an easy food supply can attract a crowd. The wildlife might become dependent on the food source and learn to associate people with food, which could lead to other problems. Also, unnatural crowding is a set-up for the spread of wildlife diseases. The 2003 ban on deer feeding, for example, was put in place to try to prevent the spread of chronic wasting disease to New York State. Report illegal feeding of wildlife to DEC Bureau of Wildlife or law enforcement staff.
  • “Animal-proof” the trash. In general, this means you can either keep garbage cans and dumpsters in protected locations, or use strong containers with secure lids. Obviously, a container that’s strong enough to keep out mice may not even slow down a bear, so match your approach to the species. Attaching cans to posts will make them harder to tip over.
  • Clean garbage cans, chutes, and dumpsters often. Check for cracks and holes. If you find any, repair them.
  • Don’t leave trash out all night for a morning pick-up. Many of the nuisance species who rummage through trash are nocturnal. If you can, put the trash out right before it’s due to be collected.
  • Enclose compost piles in a framed box using hardware cloth, or in a sturdy container. Don’t compost meat products or cooked food.
  • Feed birds during the fall and winter and gradually stop by April. Use sturdy poles for bird feeders. Keep the area underneath the feeder clean. Or use natural landscaping to provide good bird habitat instead. (See the National Wildlife Federation’s backyard wildlife habitat program for information.)
  • Feed pets indoors. Any food left outdoors should be removed at night. Bring the food bowls indoors.
  • Clean up spills of food, bird seed, grain, garbage. Promptly.
  • Remove and properly dispose of livestock carcasses immediately.
  • Store food, bird seed, pet food, and grains in strong containers. Keep stored items off the floor and away from walls.
  • Near buildings, rake up and remove fruits and nuts that fall off trees.
  • Keep livestock feeding areas and grain storage areas as clean and secure as possible.
  • Remove dog, cat, and horse droppings daily. (Feces are food to other animals.)
  • Eliminate pools of standing water.
  • Keep livestock in protected areas, especially when they’re ready to have young.
  • Switch to landscape plants that the nuisance animal doesn’t find as tasty.
  • Limit their shelter. Maintain a foot-wide gravel border around the foundation that’s free of plants (best) or at least keep foundation plantings well-trimmed. Don’t stack anything against the foundation.
  • Remove brush piles, junk piles, and clutter. Keep woodpiles away from buildings.
  • Keep a clean border around any vulnerable area (building, garden, field, orchard). Mow the grass often. Trim shrubs.
  • Mow openings through large patches of thick ground cover. Some animals don’t like to cross areas where they can be easily seen. Canada geese, however, would make good use of such openings, so don’t use this technique if geese are, or could become, a problem in the area.
  • Trim or thin trees to reduce their appeal as roosts.
  • Cut trees that brush up against the building and limbs that overhang the roof.
  • Wrap guards around trees to keep animals from climbing them. (Best done in late fall, when the wild animals have finished nesting in the tree. Keep the wrap loose so it doesn’t girdle the tree.) This will only prove effective if the tree is insulated enough that animals cannot climb a nearby object and leap into the tree.
  • Plus all the exclusion techniques to keep animals out of buildings, gardens, livestock areas, or any other vulnerable location.

Prevent future problems: Exclusion

Animal-proofing is the best way to prevent damage to buildings, gardens, livestock areas, and valuable agricultural fields. Before you start, there are a few things you need to consider.

  • Is the animal in or out?

You don’t want to trap animals inside because that can lead to worse problems. If you’re not sure whether an entry site is active, monitor it for at least two days.

Place a “soft plug” over the hole, such as newspaper, cardboard, or duct tape. Or sprinkle flour on the floor. If you don’t see any signs of an animal trying to force its way through the plug, or any tracks in the flour, then you can be reasonably certain there’s no wildlife inside—except during the winter. Many animals are less active then, and may not go out on a daily basis.

  • Are there “hibernators” in there?

In winter, many animals, such as bats, woodchucks, raccoons, chipmunks, skunks, and snakes 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.

  • Any young inside?

The downspout was removed so the one-way door could be installed right in the animal’s travel route. Great idea! But if there are young inside, that female will be very motivated to find another way back into the house. She might damage the building to return to her young.
During the spring and summer, the presence of young animals can complicate exclusion. Listen for their sounds, such as high-pitched squealing or chirping, in such places as walls and fireplaces. Another sign, if you can get close enough, is the condition of the female’s teats: they’re usually bigger and free of hair when she’s nursing. Do your best to avoid creating wildlife orphans. Special care is needed to remove young from buildings.

  • Does it work?

The durability and effectiveness of an exclusion technique varies by species and situation. For example, bats usually can’t chew or claw their way through most exclusion materials. But they’re very good at finding tiny, overlooked holes. Raccoons and rodents, on the other hand, are often able to chew or claw through a hasty repair job, or break in by creating a new hole. Be sure your methods are appropriate to the situation.

  • How does it look?
Can you see the bird exclusion product? The thin spikes are barely visible along the curved ledge. Pigeon droppings would certainly detract from the looks of this historic building far more, and are acidic enough to damages sculptures.

Can you see the bird exclusion product? The thin spikes are barely visible along the curved ledge. Pigeon droppings would certainly detract from the looks of this historic building far more, and are acidic enough to damages sculptures.

Some customers will be concerned about choosing options that don’t detract from the looks of the building. But don’t sacrifice effectiveness just for the sake of attractiveness. For example, if something’s chewed a huge hole through a piece of woodwork, just putting up fresh woodwork may not solve the problem. Covering the new wood with metal might be a better, though less attractive, choice (you can disguise the metal by painting it).

The downspout was removed so the one-way door could be installed right in the animal's travel route. Great idea! But if there are young inside, that female will be very motivated to find another way back into the house. She might damage the building to return to her young.

The downspout was removed so the one-way door could be installed right in the animal’s travel route. Great idea! But if there are young inside, that female will be very motivated to find another way back into the house. She might damage the building to return to her young.

  • Can I do the job safely?

Remember the issues discussed in chapter four? You might want to limit roof work during the winter, for example, or seek assistance from someone with needed skills or equipment.

  • Are the products and exclusion techniques legal?

Building codes, fire codes, and other local 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, and some communities ban fences or limit their heights. The legal fence may not solve your customer’s problem.

  • Will I need any special tools?

Most exclusion work can be done with general carpentry tools such as hammers, staple guns, screwdrivers, caulking guns, pliers, and tin snips. In addition, you may want to have two battery-powered drills. Why two? First, because you want a back-up in case the battery runs low in one of them. But having two drills can make your work go faster, too. For example, if you need to attach sheet metal to a building, you could use one to drill the holes in the sheet metal and the other to drive the screws into the building. If you used only one drill, you’d have to change bits between these two tasks, which would take longer.

A foam gun (such as the Todol® foam gun) is also recommended. This tool helps you spray expanding foam insulation into cracks and cavities quickly and cleanly. It’s particularly useful for bat exclusion.

  • Will I need any special products?

Yes! There are many materials available that can be used to repair holes in buildings, to screen vulnerable chimneys or vents, or to create barriers around yards and landscape plants. These products vary in their effectiveness, cost, durability, flexibility, and attractive-ness. And, of course, some are more suitable for use with certain species.

Consider an animal’s size, habits, and abilities before you choose a product. Bats, for example, would be top bets for winning a limbo contest. They can squeeze through cracks that are 1/4″ wide by 1 1/2″ long, which is about the size of a stick of gum. That means you’ll have to search thoroughly to find all of the possible entry sites. Bats, however, would be a poor bet in a chewing contest. They don’t chew holes in buildings, and they aren’t likely to chew through whatever you use to plug a hole, so you can use products such as caulk or expanding foam to bat-proof a building.

Now imagine you’re trying to exclude mice from the same building. They’re roughly the size of some of the small bats, but their abilities and habits are entirely different. Mice could probably chew through caulk so it would be better to use something more durable, such as hardware cloth. Raccoons are strong and can tear off chimney caps that deter squirrels and birds.

NWCOs differ from many building contractors in their expertise in two areas: animal habits and wildlife exclusion devices. Even if you don’t want to do the repair, help your customers understand which products to use and how to install them effectively, or recommend a knowledgeable contractor.

Here are some of the products available for excluding wildlife from buildings and landscapes.

To seal holes, cracks, and gaps:

Galvanized sheet metal is durable and, when attached with screws, resistant to removal by raccoons and other animals. But it can be hard to bend and fit around corners.

Galvanized hardware cloth (or “metal mesh”) is easier to shape than sheet metal and is reasonably durable. Hardware cloth is generally available in quarter-inch and half-inch mesh sizes. Half-inch hardware cloth is stronger but less flexible than quarter-inch. To keep smaller animals, such as bats or mice, out of an area, use quarter-inch hardware cloth. Hardware cloth is often used to create fences.

Stainless steel or vinyl-coated hardware cloth are stronger than galvanized, and will never rust. The disadvantages of stainless steel are that it’s much more expensive and harder to cut and shape.

Vinyl-coated, welded wire mesh is even stronger than hardware cloth. It lasts longer and will never rust (one manufacturer guarantees its product for seven years when used in the ocean), but it is more expensive than hardware cloth. Welded wire mesh is sold in rolls and is available in different heights, gauges, and mesh sizes. Some NWCOs prefer to use welded wire mesh to create rat walls and for any other installation that’s meant to last a long time. Recommended size for larger animals is 1 × 1″ mesh, while 1/2 × 1/2″ mesh is suitable for most smaller animals.

Aluminum flashing is flexible and relatively easy to shape around corners. It’s best for bird and bat exclusion because raccoons and rodents can usually chew or claw through it. Other exclusion materials include caulk, sealant (for movable joints), copper mesh (this resembles steel wool, but doesn’t rust; typical brands include Stuf-Fit™) and expanding foam insulation. These materials are great for sealing cracks and other small openings.

To protect vents:

Animals frequently enter buildings through vents. Replace damaged and vulnerable vents with sturdier, more animal-proof designs. Some vents can be modified with homemade screens. For example, you could attach quarter-inch hardware cloth to screen a kitchen hood vent, or protect an attic fan. Just be careful that you don’t reduce the amount of ventilation too much when you’re modifying a vent, especially with dryer vents. This could increase the risk of fire. Check the requirements for each piece of equipment before you modify the vent.

Lomanco 750 roof vent.

Lomanco 750 roof vent.

Roof vents (or louvers) should be made of either metal or heavy-duty plastic. The best models are totally enclosed to prevent birds and rodents from nesting inside them. There are also commercial stainless steel box screens that are secured over existing vents.

A ridgeline vent.

A ridgeline vent.

Ridgeline vents come with end caps that frequently work loose. This allows small animals, such as sparrows, mice, and bats to easily get inside attics. Replace the caps to secure these vents.

Soffit vent seen from below.

Soffit vent seen from below.

A wide range of animals, from sparrows to raccoons, often find their way into a building through the ventilation openings in soffits that are located under the eaves. Securely attach metal louvers to the soffit to protect these openings, which are also called “soffit vents.”

Plastic gable louvers on the sides of buildings should be replaced with metal gable louvers. The gaps between individual louver slats should be narrow enough so birds can’t nest in them. Screen the back (inside part) of the vent to keep bats and insects out of the attic.

Clothes dryer vents are another popular route indoors used by small animals. Be careful when screening these vents, because lint buildup can damage the dryer and cause fires. Clean the screen frequently or choose a vent design that prevents lint build-up while still excluding animals.

Sewer vent covered with a pipe shield

Sewer vent covered with a pipe shield

Sewer vent pipes can be covered with commercial shields to prevent rodents and birds from entering the building by slipping through gaps next to the pipes.

To protect chimneys:

Left, Chimney cap that attaches to the outside of a tile liner. Right, chimney cover with top-sealing damper.

Chimney cap
Top sealing damper type chimney cap

Raccoons, squirrels, bats, many birds, or any animal that dens or nests in a cavity (such as a hole in a tree) will sometimes go down a chimney flue. You can prevent this by installing a chimney cover on the top of the chimney. Commercial models will meet fire codes. Most chimney covers are made of stainless steel or galvanized steel, but there are copper and aluminum models. Some work both as a cover and a damper.

Many chimney cover designs attach to a single tile flue liner. These generally bolt to the outside of the tile liner, or have legs that slip inside the flue. Covers that slip inside the tile liner keep squirrels and birds out, but raccoons can usually remove this kind of cover. If raccoons are a problem, choose a chimney cover that bolts to the side of the flue. Choose models with the smallest openings allowed by fire codes to exclude bats.

Other chimney covers attach to, or around, the top of the chimney. These covers are very helpful if there are several flues in each chimney, or if there are no tile liners extending through the top of the chimney.

There are commercial covers designed to fit metal chimneys. With care, you should be able to enclose the metal chimney cover with half-inch hardware cloth. Several chimney cover manufacturers are able to custom fit covers for unusual chimneys (for a price, of course). Call the manufacturer to find out which chimney measurements are needed.

To protect alcoves, ledges, and other places that attract birds:

Netting is often used to deny birds access to alcoves and other spaces. Bird netting is made from a variety of materials (including polyethylene twine and extruded polypropylene). It’s available in different grid sizes and strand width, with specialized hardware to attach the netting to many kinds of materials.

Netting is often the most effective method to control bird damage. The cost varies a lot. Up-front costs may be quite high, because of the labor needed to install the netting (it must remain taut over time, which takes some doing), but it’s often economical in the long term. The material tends to last three to ten years.

By converting a flat perch into a sloped one using a piece of wood or a plexiglass panel, you can deter birds from landing on ledges and ornamental architectural features.

Spikes and coils turn ledge into uncomfortable roosts. (Bird-Flite® Spikes and Bird Coil® from Bird Barrier™.

Birdbarrier bird spikes on a sign
Birdbarrier birdcoil on ledge

Metal or plastic spikes help prevent birds from roosting on ledges, roof peaks, window sills, signs, and ornamental architectural features. “Porcupine wire” is a device with sharp stainless steel prongs sticking out in many angles (i.e., Catclaw®, Bird-B-Gone®, ECOPIC®, and Nixalite®). Metal coils, which look like a slinky, work the same way.

“Post-and-wire” grids discourage birds from landing in an area. The grid is made of stainless steel wire, thin cables, high-tech braided fishing line, or 80+-pound test monofilament lines. (Maintaining tension is essential, so steel wire is a better choice for a permanent installation because it will need less maintenance. Monofilament line stretches and can break.) The cables are stretched tightly over the vulnerable area in a square pattern, as parallel lines, or just as a single line across a narrower area, such as a ledge. Birds react differently to this exclusion technique. It works best to discourage gulls, crows, and pigeons from such areas as rooftops, ledges, landfills, courtyards, and fish hatcheries. If using metal, consider the possibility that this installation could be a lightning hazard.

Birdbarrier birdwire

About a half-dozen cables were stretched across this wide ledge, supported by four posts. This shows the parallel line installation. On a narrow ledge, one cable might be enough.

Electric shock devices (Avi-Away®, Flock-Shock®, Flyaway®, VRS®) deliver a nasty enough shock to be taken seriously, but they don’t kill the birds. They’re used to keep birds off ledges. The cost of installing these systems is often high, but the systems generally have a long working life.

Commercial plastic strips can provide bird-proof barriers for doors to warehouses, grain storage areas, and other buildings. These strips can be hung from the top of the doorframe to ground, allowing people and equipment to easily pass through the door.

To protect outdoor areas:

Fences tend to provide the most effective exclusion. They can be made of many materials, such as woven wire, hardware cloth, electrified wire, rope, bird netting, or some combination of materials. Fences vary dramatically in design and cost. This device works on both a small scale (individual plant) and a large scale (garden, field, orchard, park). Some are permanent installations while others are temporary and portable. Permanent fences require maintenance. All fences need to be adequately secured.

The most effective fences are designed with the particular abilities of the target animal in mind. For example, does it jump or burrow? Repellents will sometimes be used in combination with a fence. A cloth dipped in repellent may be tied onto a rope fence, for example—adding oomph to a cheap and simple fence (but that does qualify as a pesticide).

Tree wrap, tree guards, and chicken wire cages, and hardware cloth can be wrapped around trees and shrubs, or draped over individual plants to protect them from being chewed or girdled. Keep the mesh about an inch away from the plant so it has some room to grow. Don’t staple the material to the tree because that could lead to rot. Later on, if someone wanted to cut that tree down, the staples could prove dangerous.

This fence design, called a rat wall, is often attached to foundation, deck, porch, or installed as a free-standing barrier around a garden area. Rat walls are effective against a variety of animals including skunks, woodchucks, raccoons, squirrels, and rats. Match the size of the mesh to the size of the animal you're trying to exclude.

This fence design, called a rat wall, is often attached to foundation, deck, porch, or installed as a free-standing barrier around a garden area. Rat walls are effective against a variety of animals including skunks, woodchucks, raccoons, squirrels, and rats. Match the size of the mesh to the size of the animal you’re trying to exclude.

The top of the fence is attached to a structure. The bottom is buried 6-12 inches deep. Notice that it’s bent at a 90O angle, forming the letter “L”. This shelf helps to stop animals from digging under the fence. The shelf should stick out 6-12 inches.

One-way doors can be “installed” in the rat walls to release the animals. First, attach the rat wall. Leave one or two locations open, and install one-way doors there. Make sure the animal can’t dislodge or dig underneath the one-way doors. When there’s been no sign of animal activity for several days, remove the one-way doors and finish the exclusion. (An easy way to test for animal activity is to put some nontoxic tracking powder or flour on the ground under the porch, in the animal’s route. Check later for tracks.)

Prevent future problems: Monitoring

Here’s a strategy that has a key role in modern agricultural pest management, which might be very useful for NWCOs, especially those who service apartment complexes, large properties, or have corporate accounts. It may give you the chance to use your knowledge to promote a better approach to wildlife damage management. This can be good for your customers, for wildlife, and for your bottom line, all at the same time.

Monitoring refers to the routine inspection of a site to evaluate its current condition and look for vulnerabilities that could lead to wildlife conflicts later on. You gather the information your customer needs to make better decisions, then offer advice. Monitoring often helps people save money because you catch a problem when it’s small and easier to manage, or better yet, you prevent it from happening altogether.

In agriculture, pests aren’t controlled until monitoring reveals that their activity has reached a certain level—above the threshold, the point at which it pays to deal with the situation. In some cases, thresholds are very precise: “four flies on each leg of the cow counted during a ten-minute period,” for example.

So how does this apply to nuisance wildlife control? Your customers are probably most concerned about three things: health and safety; economic damage; and quality of life issues. How bad does a nuisance wildlife situation have to be in order to justify control? You may be able to sit down with your customer and establish your own guidelines. Your customer might be willing to tolerate woodpeckers banging on a metal gutter but not squirrels in the attic, for example.

Or maybe you just skip the idea of thresholds altogether because your customer doesn’t want any wildlife damage at all. Instead, you just agree on an inspection schedule. Your goal is to prevent problems. After a very thorough initial inspection, maybe you go out once a month. Homeowners might be willing to pay for an annual inspection.

Since monitoring isn’t widely used in nuisance wildlife control work, you may need to explain the idea to convince your customers that this is a best practice. Pictures showing actual wildlife damage can help people understand the economic risks. Let them know how much the repairs cost for each of those situations. Compare that to the cost of an inspection. The best way to solve a wildlife conflict is to prevent it. Monitoring might be a way to achieve that goal.

Next Section Evaluating Success


Handbook Contents


Needs of People and wildlife

  • Six Questions NWCOs must ask

Federal Laws and Regulations

Safety Risks for Customers

Best Practices for Wildlife Control

Resources for NWCOs


This manual was written as a guide to train nuisance wildlife control operators in New York State. Laws and regulations may differ in your state. Always consult local and state laws before implementing wildlife damage management activities.

Contact Information

Contact your local Extension Office


Internet Center for Wildlife Damage Management
National Wildlife Control Operator’s Association
Wildlife Control


We thank the New York State Department of Environmental Conservation for contributing this information.

Produced by the NYS Department of Environmental Conservation, Cornell Cooperative Extension, and the NYS Integrated Pest Management Program.