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 three: Do it (tools and techniques)
With your overall problem-solving strategy in mind, now it's time to choose the techniques that will help you accomplish your goals. If you decided to do nothing, well then—you're done. If you'd like to make the environment less attractive to the nuisance animal, you'll find more suggestions listed in the species accounts in Appendices B and C. This manual won't go into any more detail about methods used to reduce local wildlife populations, but you can learn more about that from some of the resources listed in Appendix E. In this section, we'll explain some of the best practices for repelling, removing, excluding, and killing animals.
Avoid creating wildlife orphans
Foxes often calm down once they're restrained with a catchpole. Since this healthy fox had accidentally wandered in, it was released on site. Before you repel, remove, exclude, or kill an animal, take steps to prevent the orphaning of young wildlife. A lot of NWCO work happens when wildlife are raising their young, so this is an important consideration. Sounds pretty reasonable. How do you do it?
Unfortunately, this is another hotly debated topic that hasn't been well-studied. For raccoons and squirrels, there's some anecdotal information tracking the number of times a female will retrieve her young when certain removal techniques are used, but to our knowledge, no one has followed that all the way through to find out what happens later. How often does the female find a suitable den site in time? How easily does the family recover from the stress of the experience? Do a reasonable number of the young survive to adulthood?
Many people assume that den and nesting sites are plentiful and that females usually have several "up their sleeves." Perhaps this is true for some species, in some areas. It's certainly not true in all places.
The best way to prevent orphaning is to convince your customers to wait until the young are mobile before removing, repelling, or excluding the family from the site. If that's unacceptable, you can try to capture and remove both the female and all of her young and hope that she will retrieve them and continue to care for them.
When is this most likely to work? Let's apply a little biological common sense. Older, more experienced females are probably better at finding resources than younger females. As the young age, they bond more closely with their mother, so she'd be less likely to abandon them. You can't change the ages of the animals you're dealing with, but if you think your chances of success are poor, you might choose a different option.
Some NWCOs are trying to refine removal techniques to increase the chances that the female will retrieve her young. Here are their suggestions.
- Time your activities to match the normal habits of that species. The sooner the female finds the young, the better. If they're left alone too long, they may die of exposure. For a nocturnal species, start at dusk.
- Remove the female, preferably using a direct capture technique such as a catchpole (described later).
- Place the female and young in a release box. (We'll describe several variations on this theme.) Many NWCOs use a simple cardboard box, others use a wooden nest box, such as a wood duck box, and some prefer plastic boxes.
- Match the size of the box and its entrance hole to the size of the species, using a smaller box with a smaller hole for squirrels, and a larger box with at least a 7" hole for raccoons. (One NWCO recommends a 2 × 2 × 1 ft. box.)
- Make sure the animal cannot immediately get out of the box by covering the hole. Then move them to a quiet place outdoors. Unless they're likely to be disturbed, keep the box at ground level. Remove the cover so the female can get out of the box. Another option is to build a box with a sliding door. Leave the door open about an inch, to keep the heat inside but make it easy for the female to slide it fully open so she can retrieve her young.
- Some NWCOs prefer to use heated release boxes when it's cold outside. Make sure that the box doesn't get too hot. You may want to provide heat in just one area. Also, assume that if you put something in the box, they will chew on it. Don't give them access to anything that they shouldn't eat, such as wires. That means that if you choose to use a household heating pad as the heat source, make sure the animals can't reach the wires. To avoid that problem, one NWCO builds his boxes with a double floor, placing the heating pad in the space between the floors. Other options for heat sources include microwaveable heating pads and warm soapstones.
- If you can't catch the female, put the young in the release box and locate it as close to the entry site as possible.
Learn the typical birthing and rearing seasons of the species you handle. Know how to tell when a female is nursing and what young sound like. How will you evict the animals? The next section is an overview of the common techniques available to NWCOs.
Nonlethal techniques: Direct capture
Sometimes, you may be able to capture the animal immediately, using your hands or a simple device, such as a catchpole. If you can do so safely, this is often appealing to the customer. It may also eliminate the need for repeated visits to the site. Remember all of the safety tips from chapter four. The right gloves are especially important if you're going to try to catch an animal by hand.
Other useful devices include: catchpole combo | buckets | nets | drugs
Catchpole, or "snare pole" (similar to snake tongs, cat grasper). This is one of the most versatile tools used to capture and restrain animals. Basically, a catchpole is a long stick with a noose (cabled loop) on one end. For most species, place the loop over the animal's head and then tighten the cable to hold the animal. Bobcats and housecats can accidentally suffocate if the loop is only placed around their necks—it's better to place the loop over the cat's head and over one front leg. Minimize the amount of time an animal spends in this restraint.
Some catchpoles swivel, allowing the animal to twist without being suffocated. Commercial catchpoles often lock once you've pulled the cable tight, and also have a quick-release. (If you prefer to make your own, run a loop of plastic-coated cable through a piece of rigid aluminum pipe or conduit that's 3–4 feet long. You may still want to add a quick-release mechanism.)
Related hand-operated devices may substitute a vice-grip closure for the noose on the end of the catchpole. Imagine the kind of pincer that some people use to grab cans off a high cabinet. This can be useful if you're trying to capture a small animal, such as a squirrel, or if you can only reach a part of the animal and would not be able to get a loop around it. Poles with this vise-grip closure usually don't have the restraining power of catchpoles.
Modified catchpoles are available for restraining snakes. They're often called snake "sticks," "tongs," or "hooks." These devices pin the snake's head to the ground. Use them carefully, because it's hard to tell how much pressure you're exerting so you could accidentally injure the snake's spine or even dislocate its head. Once the snake's head is restrained, grasp the snake just behind its jaws with your thumb and forefingers. This will give you control of its head. Support the snake's body (with your arm, a stick, or a pole) when you carry it. This will minimize its stress and prevent it from thrashing about.
What if you're confronted with a large nonvenomous snake, such as a boa constrictor, that's tightly wrapped around a person? If you can't work it loose with your hands, remember that snakes don't like cold temperatures. So have the person step into a cool shower. The snake will probably let go once the water hits it, and try to slither away.
Obviously, inexperienced people should not handle venomous snakes! NWCOs with the proper snake-handling training should still take a few precautions when working with venomous snakes.
Don't work alone. If you must, at least tell someone what you're doing. Call the local hospital before you go out on the job, to see if they have the proper antivenin—and have them check that it's still good (they probably don't use it often, so it could be outdated). Bring along a garbage can with a lid, or a cage that you can put the snake in once you've captured it. One final tip: of the three species of venomous snakes native to New York, two are legally protected (timber rattlesnake, eastern massasauga) and may not be handled without special state permits.
A "catchpole combo." Many NWCOs are talented tinkerers. In this case, one person combined simple tools for a unique direct capture technique used to remove a raccoon from a fireplace chimney in one visit. This method requires a catchpole, a chimney brush attached to flexible fiberglass chimney rods, a ladder, and gloves.
Make sure the damper is securely closed. Climb onto the roof. Run the chimney brush (attached to flexible fiberglass chimney rods) down the chimney. When the brush enters the smoke chamber and drops to the damper, it opens up an escape route for the raccoon. As the coon climbs up into the flue, pull the brush up behind it to encourage the coon to move up the chimney. (The faster the brush is pulled up, the less likely the animal will try to force its way down past the brush.)
When the raccoon is four or five feet from the top of the chimney, use the catchpole to capture it and transfer it to a holding cage (usually a cage trap). Then, if there are young in the chimney, go inside the house. Open the damper and remove them with your gloved hands.
Buckets or small plastic containers. This works well with bats and small snakes. Cover the animal with the container, and then slip a piece of stiff cardboard between the container and the wall or floor. You can then carry the animal outside and release it (remember: don't release bats if there was a possible rabies exposure).
Nets. Two designs are the throw net and "hoop" net. Throw nets are tossed over the target animal. Hoop nets are attached to the end of a long handle. They're used to scoop up the animal. The net should be deep enough to allow the hoop to be twisted to restrain the animal in the bottom of the net. A captured animal may climb out of a shallow net. The size of the mesh is important, too. If the mesh is too large, the animal may force its head through and injure itself or strangle. If you must use a shallow net, immediately place the frame against a flat surface to prevent escape. You can further restrict the animal's movement by carefully pressing on it with a stick. Whenever possible, encourage the animal to enter the net on its own. You might injure an animal while swinging a hoop net, if you accidentally hit it with the frame.
Very few NWCOs have access to drugs (such as ketamine hydrochloride, tiletamine, alphachloralose, and metatomadine) that can be used to capture an animal directly. These "immobilizing agents" are heavily regulated by federal and state agencies. NWCOs with the proper training work under the supervision of veterinarians, who have the necessary permits from the U.S. Drug Enforcement Agency. In New York, permits are also required to use syringes and needles. Staff from USDA-APHIS-Wildlife Services may provide technical assistance for bird capture programs involving alphachloralose.
Although these drugs are not available to most NWCOs, they may increase the operator's safety while reducing the animal's stress. But things can go wrong, even for highly trained and experienced people, because when you're working in the field, you have less control of the situation.
For more information about alphachloralose, contact: USDA-APHIS-Wildlife Services
Nonlethal techniques: General trapping tips
- The trap design should be matched to the species and to the situation.
- Always choose trap types that minimize the risk of catching unintended wildlife species or pets.
- Leave a phone number so your customer can reach you in an emergency.
- Set traps (including cage traps) so that children and domestic animals can't reach them. Either may harass captured animals and possibly get bitten.
- Be discreet; keep traps out-of-view of the general public.
- Secure and label all traps with your name and address (required by law).
- Take steps to protect captured animals from bad weather including summer heat, rain, snow, and cold. Covering a trap or setting it in a more protected location can help.
- For the most common nuisance species, you don't need to worry as much about getting human scent on the traps. Consider where they're living and what they do—they're used to people.
- The proper use of baits and lures may increase your capture rate and help you avoid capturing animals you didn't want to trap.
- To prevent trapped animals from reaching through the cage and tearing up turf or nearby objects, place the trap on pavement, or put a large piece of hardware cloth underneath the trap.
- Take steps to avoid orphaning wildlife.
- Set traps where they're most likely to capture the target animal and not others. ("Location, location, location.")
Nonlethal techniques: Live traps
Live traps are effective devices for capturing many species. Shown here are a raccoon, opossum, and woodchuck in the back of a NWCO's truck. Notice that cardboard placed between the cage traps to keep the animals from seeing each other. This may reduce their stress during transport.
This is probably the animal removal tool used most often by NWCOs. A live trap is meant to capture an animal without killing it. Some types of live traps are cage traps (also known as "box traps"), multiple capture traps, foothold traps, nets, and a variety of bird traps.
Live trapping has some advantages. You can see what you've caught, and prove your success to your customer; and it prevents animals from dying in inaccessible locations, one of the hazards of using pesticides. In addition to the foul odor caused by decay, the presence of a dead animal can attract other pests. In most cases, if you're using a live trap, you would be able to release an animal that had been caught accidentally.
There are some disadvantages to live trapping as well. It's usually labor-intensive, and you might capture the wrong animal. If the live trap is used improperly, an animal may die in it, from lack of food or water, exposure to heat during the summer, weather extremes, or from attacks by wildlife, pets, or people. Some animals might hurt themselves because of the stress of being restrained, or while trying to escape.
If you're not experienced with live traps, we strongly recommend that you seek hands-on training—especially before using foothold traps. There are several excellent courses, including the DEC Trapper Education Course, and the Trapper's College and Furbearer Management Short Course offered by Fur Takers of America. Sessions on trapping techniques are often incorporated into seminars, conferences, and conventions sponsored by NWCO associations and trapping associations (see the resource list for state and national contacts). There are opportunities for one-on-one instruction, too. Experienced trappers often advertise such services in trade journals. You'll also find many books, videos, and magazines about trapping. Consider reading Trapping in the 21st Century.
Cage trap in set position.
Cage traps (a.k.a. "box traps") are the main stock-in-trade of most NWCOs. These traps are often made of wire or plastic and come in many sizes and styles. They may open on one, or both ends. Customers may call all cage traps "Havaharts" after a popular model, but there are many designs and manufacturers, such as Tomahawk and Safeguard. For example, there are special, smaller versions of squirrel-sized cage traps that fit into woodstoves and chimney pipes.
An animal enters the cage, then steps on a treadle, which causes the door(s) at the end(s) of the trap to close. Cage traps are easy to set and do double duty as a carrier. Little site preparation is usually needed. They are generally safe for children and pets. Most people think they're humane. Unfortunately, most cage traps are bulky, and because of their size and shape, they're hard to conceal. This makes them more vulnerable to theft and vandalism. They are relatively expensive, and need frequent cleaning. Cage traps are not universally effective in capturing animals. Some species, such as foxes, are usually shy of these traps. Even individuals of species that are generally easy to catch in a cage trap, such as raccoons and gray squirrels, can be "trap-shy," especially if they have been captured before.
Tips for live trapping mammals in an attic using a cage trap.
- Set the trap on the roof, as close to the entry hole as possible. Why not in the attic? Because adult raccoons seem to be less wary of traps on the roof than they are of traps placed in attics or on the ground.
- With a roof set, you can safely use a few baits that wouldn't be recommended for a ground set, such as pet food, because non-target animals aren't as likely to go up on a roof. Avoid oily fish products such as sardines, because they might stain the roof.
- With a roof set, you can also check the trap from the outside of the building.
- How will you keep the trap from sliding off the roof? If the owner agrees, drive screws part way into the roof, then wire the trap to the screws. Once the trap is secure, finish driving the screws into the roof, then dab some roof sealant onto the heads of the screws.
Tips for live trapping mammals on the ground using a cage trap:
- Set the trap in the animal's travel path, or in an area the animal uses often. (Look for sign.)
- Choose a bait that will appeal to the target animal but not attract unwanted animals. For example, pet food attracts raccoons—and cats and dogs. If you want to trap a raccoon, a better option might be marshmallows, which aren't as enticing to cats. Eggs are sometimes used as bait for skunks. Apples or raw vegetables are good woodchuck baits.
- Covering the bottom of the trap with soil or leaves may also convince an animal to enter.
- Raccoons may respond to a visual attractant such as a piece of aluminum foil suspended from the roof of the trap.
- There are many commercially available scent lures. Just be aware that lures may attract unwanted species, too. NWCOs tend to use lures when they're dealing with a trap-shy individual, or must set their trap away from the nuisance animal's favorite areas.
- After you have the trap set and baited, "dry fire" or trip the trap. Make sure the trap door(s) close smoothly and firmly.
This trap (Lil' Grizz Get'rz™) takes advantage of the coon's dexterity. Many animals can stick their paws into a "hole" (the trap), but most can't grasp and pull out an object that's within. Coons can. The object is the trigger, and they'll try to pull it out, which fires the trap.
Multiple capture traps are able to catch more than one animal without having to be reset. Most multiple capture traps are designed for mice. Some brands (such as Ketch-All®) will catch animals up to the size of chipmunks. However, larger animals are likely to suffer harm. Some designs (such as Ketch-All® and Kwick Katch®) have a wind-up spring that powers a rotating mechanism. The mice are shuttled into a holding compartment. Other traps (such as the Victor Tin Cat®) have one-way doors that allow mice to enter, but not leave. If you intend to use this as a live trap, you must ensure that it's checked often enough so that animals don't overheat and die in the trap.
Foothold traps restrain animals by holding the foot. Foothold traps can be used on land and in the water. In nuisance wildlife control in New York, they are the most efficient tools for catching coyotes and foxes, and are also important for raccoon, beaver, and muskrat. There are several different designs, including the coilspring trap, which is probably the most commonly used foothold trap; the longspring trap; and several new cylindrical foothold traps (Lil' Grizz Get'rz®, Duffer trap®, EGG trap®) meant specifically for raccoons. These cylindrical foothold traps reduce the chance of catching the wrong species and the risk of the raccoon injuring itself.
To set a coilspring trap, you must fully depress the spring levers. This compresses the springs. Then, place the dog across the nearest jaw until the tip of the dog fits into the notch of the pan. The dog holds the trap open in its set position. When an animal steps on the pan, it dislodges the dog from its notch and springs the trap, closing the jaws around its foot.
Left. a coilspring trap, a type of foothold trap, shown in its set position. This live trap is shown in its sprung position at Right.
Above, a coilspring trap, a type of foothold trap, shown in its set position. This live trap is shown in its sprung position at left.
In some cases, modifying a standard coilspring trap by padding or laminating the jaws will reduce the chance of injuring the captured animal while possibly increasing the effectiveness of the trap. There are commercial models available with these modifications, too. Many NWCOs also add at least one swivel between the trap chain and the stake that anchors the trap to the ground. These swivels allow the captured animal to move around without binding the chain and twisting its leg. (Most within the chain are double swivels, but single swivels are usually used at the end of the chain.)
Adjusting the pan tension on coilspring traps helps reduce the chance of capturing the wrong species (an animal that weighs less than the target species should be able to step on the pan without triggering the trap). There are several ways to adjust pan tension. With some trap designs, you can tighten or loosen the pan tension screw, which controls the amount of pressure needed to spring the trap. The tighter the screw, the heavier the animal must be to spring the trap.
In New York, there are legal restrictions on the jaw spread of a foothold trap. The jaw spread is the distance between the two jaws when the trap is set (not counting the thickness of each jaw's gripping surface). A foothold trap set on land is allowed a maximum jaw spread of 5 3/4 inches; in water, the jaw spread cannot be greater than 7 1/4 inches. There's another restriction for foothold traps set on land in New York: if the trap has a jaw spread of 4 inches or larger it must be equipped with a pan tensioning device and must be covered with some material such as soil, sand, or leaves.
Birds. Nets are usually used to capture birds, such as sparrows and starlings, inside warehouses. To use one type of fine-threaded net, called a "mist net," you'll need training, skill, and a permit (it takes skill to remove a bird from a mist net without harming the bird). Unless you have the appropriate federal and state permits, a NWCO should NEVER use a mist net to try to capture wild songbirds outside. Mist nets should be monitored during use and removed immediately after. Even veteran users can become frustrated trying to capture a sparrow or two in a net inside a large warehouse.
Bird live traps are available in many designs. Most are designed to capture particular types of birds. Some will capture one bird at a time, while others can capture many birds. To increase your chance of success, give the birds time to get used to the cage trap. First, put out some bird seed, shelled corn for pigeons, or other appropriate bait to get the birds used to feeding in the area. (If the birds don't come to the site, choose another area.) Once the birds are feeding at the site, place the cage trap next to the bait and prop it open with wires. Place bait outside and inside the trap, to encourage the birds to enter the trap. Finally, when the birds are used to entering the trap, set the trap and place the bait only inside the trap. Leave one or two captured birds inside the trap as decoys. Give them shelter, and water and food, daily.
Cable restraints. This tool is not legal in New York, with one exception: with training, certification, and a special permit, a NWCO may use cable restraints to capture beaver.
Nonlethal techniques: One-way doors ("check-valves")
One-way doors may look very different, but they all do the same thing: let the animal out and keep it from getting back in. Above, left: Looking into the device, you can see its trap door in the set position. At right, the same one-way door design, used to remove flying squirrels from an attic. If you opened the left-hand side of the device, they'd leave on their own. Bottom: Mesh is often used to make a one-way door for bats. This one-way door design is usually called a "checkvalve."
One-way doors may look very different, but they all do the same thing: let the animal out and keep it from getting back in. Above, left: Looking into the device, you can see its trap door in the set position. At right, the same one-way door design, used to remove flying squirrels from an attic. If you opened the left-hand side of the device, they'd leave on their own.
Bottom: Mesh is often used to make a one-way door for bats. This one-way door design is usually called a "checkvalve."
These devices allow an animal to leave but not re-enter a building. They come in a variety of designs, sizes, and materials, from plastic checkvalves or nets used for bat control, to wire frames that are specially designed to fit certain cage traps. Some NWCOs build their own one-way doors. One of the advantages of using this tool is that you don't have to handle any animals. This is a relatively new tool in nuisance wildlife control, but its use is increasing.
Before installing a one-way door, conduct a thorough inspection to make sure there are no young present which are still immobile and dependent on their mother. One-way doors are only effective if the animal can find and use the exit but cannot find, or force its way back through the door—or find another way into the building. Remember, if a mother has been separated from her young and they're still inside, she will be highly motivated to find another way in.
Here's how a one-way door is used in bat control. A commercial checkvalve or simple netting is installed over the bat's primary exit hole. All the other holes are sealed. Bats exit at the bottom of the one-way door, but when they attempt to return, their sense of smell guides them back to the hole. They land on the mesh (or checkvalve) near the hole, and stay there, sniffing around. They just don't crawl down the mesh. After a suitable period of time, the one-way doors are removed, and the main entry sites are closed. (For more information, see the "house bats" account in Appendix B or the Cornell Cooperative Extension's video, The facts about bats: Exploring conflicts, designing solutions.)
Nonlethal techniques: Frightening techniques and repellents
Repellents, you may remember from the earlier discussion, are objects, substances, or techniques that frighten an animal away. Or they make the desired object, such as a crop or nesting site, undesirable—the repellent may make that object smell or taste nasty, or feel bad to the touch.
There are several tools and techniques used to repel animals: scare devices; chemicals (which can only be used by NWCOs with a commercial pesticide applicator license); hazing with dogs, hawks, falcons, or radio-controlled boats and cars; and the use of guard animals.
Objects that look scary, such as mylar tape, strobe lights, lasers, models of predators, and "scare-eye" balloons, are often used to drive off birds. Geese and crows can be easily dispersed from a night-time roost by pointing a spotlight, laser pointer, or laser pistol (such as the Avian Dissauder®) at them. Visual repellents range dramatically in price, sophistication, and effectiveness. For example, everyone recognizes a scarecrow, but there are versions that actually move. These animated "human effigies" tend to work much better than the charming homemade kind, which are better considered as garden decorations. (Whenever possible, choose a repellent that moves, such as by swaying in the wind). Visual repellents should be clearly visible.
Objects that sound frightening, include a variety of firecracker-like noisemakers and recordings of distress calls and alarm calls. Sometimes, even banging a pot or rattling tin plates will drive off birds (but not ultrasonic devices, which they can't hear). Distress and alarm calls are most effective. Before using any noisemakers, check local ordinances and consider the effects on the neighbors. Fireworks-based noisemakers (a.k.a. "pyrotechnic devices") include:
- bangers (a.k.a. "bird bombs"): makes a loud bang. It's often launched from a handheld pistol launcher. Bangers can be used at medium range (50-100 feet).
- screamers: makes a long, drawn out whistle. They can be launched from a handheld pistol launcher or a 12-gauge shotgun. The shell flies out about 100 feet, screaming and whistling all the way.
- shell-crackers (or "crackers"): makes a loud bang that sounds like a M-80 firecracker. These shells are fired from a twelve-gauge shotgun, exploding about 75 yards away.
- propane cannons: unlike the other devices, propane cannons can be used with a timer. All of the other devices must be fired by a person.
There are a few devices that combine flashing lights and scary noises, for example, the Critter Gitter®. Some of these can be very effective because they vary the pattern of the frightening element.
Chemicals that make objects smell, taste, or feel bad. You'd need a commercial pesticide applicator license to use any of these products in your NWCO business. For information about the training, contact the DEC's Bureau of Pesticide Management or Cornell's Pesticide Management Education Program.
Hazing describes a technique in which dogs, hawks, falcons, or radio-controlled aircraft and boats drive nuisance animals away from a site. Hazing Canada geese with border collies is one of the most effective ways to chase the birds away from golf courses, public parks, and similar locations. Hawks are sometimes used to chase other birds away from airport runways.
Don't haze birds in their nesting areas during the nesting season—that's a violation of the Migratory Bird Treaty Act. Be very careful if you want to haze Canada geese during their molt (usually June 15–July 15), because the geese are vulnerable and can't fly. It's wise to first secure a permit that would allow the taking of geese. Even a well-trained dog might accidentally injure a goose while chasing it. Without a permit, that's also a violation of the Migratory Bird Treaty Act.
Guard animals such as dogs and llamas are sometimes used to protect livestock, especially sheep, from predators. The livestock and the guard animal must be kept within a fenced area. Dogs can sometimes protect orchards or Christmas tree plantations or vineyards from deer or turkey damage.
You may encounter different definitions of "repellent" and "exclusion device." There is natural overlap between the two categories. Don't sweat it. We've classified products that are meant to be permanent installations, such as porcupine wire and post-and-grid systems, as exclusion devices. Although they repel birds, these devices are clearly barriers. Recordings of distress and alarm calls may have a long-lasting effect, but they are noisemakers.
Does this classification matter to anyone but an academic? Yes—because you need to remember that in general, repellents are a bit trickier to use. Although they may provide quick relief, it often doesn't last. Exclusion devices, on the other hand, often require an up-front investment because the materials and installation may be expensive. They tend to provide long-lasting results, and help to prevent problems. Exclusion can be a proactive approach, but repellents are generally a reactive strategy.
General tips for the use of repellents and frightening techniques
- Before you use any repellents, double-check their legal status at all levels: federal, state, and local. Are you dealing with a protected species (usually, a migratory bird)? Any local ordinances that come into play? For example, noise ordinances would affect your ability to make use of pyrotechnic devices, which are purposefully loud. Local bird control ordinances might affect your choices, too.
- If you want to use chemical repellents, you must follow pesticide regulations.
- Often, a combination of techniques is more effective than using one technique by itself.
- Repellents tend to be more successful in preventing new behavior (such as roosting, nesting, or feeding) than in stopping a well-established behavior.
- Another thing to remember is that animals get used to both visual and sound repellents. To increase your chance of success, mix things up a little. Move the devices around. Change the patterns of the noise or lights. Keep it unpredictable.
- Remove the devices after the problem has stopped (or if the animals have left the area for other reasons).
Just as there is no magic pill solution to wildlife conflicts, there is no one killing technique that will work best for all species or in all situations. Some methods are not appropriate for young animals or diving or burrowing animals. Some work better with birds, or reptiles, or mammals. Some require additional permits, or more than an average level of skill, experience, or strength. They may be effective for some NWCOs and not others. And if rabies is an issue, you must select your method carefully.
Sometimes, protecting people will be your highest priority. You may need to kill an animal as quickly as possible. Even in such cases, do the best you can to provide the most humane death possible under the circumstances. Most people agree that a "humane death" is one that is as painless as possible. The ideal is to be quick. Either kill the animal quickly, or cause rapid unconsciousness, then rapid death.
How do animals experience pain?
You need to know just a little bit about how animals experience pain to understand how this works. A sensation triggers an impulse that travels along the nerve endings to the brain. The brain interprets this as—ouch!—pain. (The most important part of the brain involved in the sensation of pain is the cerebral cortex, which is in the front of the brain. Other parts of the brain are involved in the feelings of fear, anxiety, and discomfort.)
The brain must be working in order for the animal to experience pain. If you can break the circuit between the brain and the rest of the body, the message will not be delivered and understood; the animal will not feel pain.
Bottom line: no working brain, no pain.
That seems straightforward so far, doesn't it? Unfortunately, there is disagreement about which methods are appropriate to kill wildlife under field conditions. There hasn't been much research that's really relevant to the situations NWCOs encounter. And to make things even more difficult, some of the methods that are well-accepted for wildlife, such as shooting, cannot be used in all areas.
Lethal techniques: Rationale for the methods included in this manual
The following recommendations are meant for the species discussed in this manual. In the species accounts in Appendices B and C, we've listed preferred and acceptable killing methods for each species. Whenever possible, use a preferred method.
Some of the lethal techniques we'll describe can also be used as removal methods, such as lethal trapping, shooting, and the use of barbiturates or pesticides. The others are strictly killing methods: the use of a carbon dioxide chamber, cervical dislocation, stunning, and chest compression.
This list reflects current scientific information and the judgment of experienced NWCOs and wildlife biologists—people who care deeply about the treatment of wildlife and have actually used these methods in the field over many years. Many factors were considered when evaluating a method. Is it as quick and painless as possible? Is the technique or product generally safe for the NWCO, the public, other animals, and the environment? Is it practical for use in the field? Does it require additional permits? Is it legal in most places? How reliable is the method? Can most NWCOs be expected to master the technique, or does it require more than average skill or strength? Although we did consider public opinion, we did not rule out techniques that don't look pretty because in some situations, these methods may provide a more humane death than a technique that looks better.
Some of these methods also meet the guidelines described in the 2000 Report of the American Veterinarian Medical Association Panel on Euthanasia. Although their report focuses on domestic animals and the techniques used to kill them in a controlled, indoor setting—it was written for vets, after all—you may still wish to read it to better understand some of these techniques. The report is available online. Click on the reference above to download the PDF file.
This is the aspect of your job that might require the most discretion. In general, it's best to work in private. If a crowd has gathered, ask them to leave, or move the animal to a private setting before you kill it. This is safer for the people and kinder to the animal, who may be stressed by the presence of the crowd. If you must kill an animal in front of others, first explain what you are doing and why.
Carry a variety of tools so you can choose from the full range of methods, selecting the one that's most appropriate for the situation. In some cases, you may use one method to cause unconsciousness and another to kill the animal.
With the exception of lethal traps and the use of pesticides, which are set and then left in place, the NWCO is able to monitor the animal to make sure it experiences as little distress as possible. Some lethal methods, such as the use of carbon dioxide chambers, may require adjustment during the process. It's also important to confirm that the animal's dead. An easy way to do this is to touch the animal's eye with a long stick. If it's dead, it won't blink.
Lethal techniques: Lethal traps
The types of lethal traps most frequently used by NWCOs are mouse and rat snap-back traps, body-gripping traps (such as the Conibear® line), and mole traps. Most lethal traps kill an animal with a mechanical blow. When properly set, lethal traps are usually highly effective and selective. Although death usually comes quickly, it's not always instantaneous. Lethal traps may work faster than cage traps, reducing the number of visits needed.
Lethal traps are appropriate for use with small to large mammals (mice to beaver size) and unprotected birds of any age. Match the size of the trap to the size of the targeted animal, but use the smallest trap appropriate for the target. The lethal traps currently available in New York are generally not suitable for use with deer, bear, coyotes, foxes, and some birds.
There are some disadvantages associated with the use of lethal traps. First, they're lethal. If you've caught the wrong animal you can't release it unharmed. If a trap is not set properly you may get a bad or nonfatal capture. It takes more skill, experience, and time to set a lethal trap (you might need more strength or setting tools). The site often needs to be prepared.
Again, if you are not an experienced trapper, we strongly recommend that you seek hands-on training—especially before using body-gripping traps. There are several excellent courses, including the DEC Trapper Education Course, and the Trapper's College and Furbearer Management Short Course offered by Fur Takers of America. Sessions on trapping techniques are often incorporated into seminars, conferences, and conventions sponsored by NWCO associations and trapping associations (see the resource list for state and national contacts). There are opportunities for one-on-one instruction, too. Experienced trappers often advertise such services in trade journals. You'll also find many books, videos, and magazines about trapping. Consider reading Trapping in the 21st Century (PDF).
General tips for the use of lethal traps
- The trap's size and design should be matched to the species and to the situation.
- Use the smallest trap appropriate for the targeted species.
- Leave a phone number so your customer can reach you in an emergency.
- Set traps so that children and domestic animals can't reach them and get hurt.
- Be discreet. Keep traps out of view of the general public. If you can't switch to a less visible place, then hide the trap with a cardboard cover. There are commercial models that are enclosed within a tunnel, which partially conceal the trapped animal (designed for squirrels).
- Label all traps with your name and address (required by law).
- Secure traps so predators can't remove them.
- At least one of the trap's jaws must be able to rotate fully.
- Take steps to avoid orphaning wildlife.
Always choose trap designs and methods that minimize the risk of catching unintended wildlife or pets. This might include using baits to selectively attract the target; placing the trap in a vertical "cubby" set, deep-notch box, or in a bucket with a restricted opening, so other animals can't reach the trap; covering the burrow entrance and trap or using a one-way trigger, so the nuisance animal encounters the trap when it tries to exit through its hole, but other animals can't reach the trap; and adjusting the trigger position to match the size and habits of the target species.
The proper use of baits and lures may increase your capture rate and help you avoid capturing animals you didn't want to trap. Baits and lures are more often used with snap-back traps.
Lethal techniques: Lethal traps - Body-gripping traps
Body-gripping traps are spring-loaded lethal traps available in many sizes. They're usually square, but some specialized models are round. Body-gripping traps are often called "Conibears," which is the name of a popular model manufactured by Oneida-Victor, Inc., but there are many manufacturers. There are also new, smaller designs, including some with one-way triggers, which are more selective, and traps designed specifically for squirrels.
"Magnum" or "zero tolerance" versions are also available. This model is stronger and its jaws close very tightly, so it often kills faster and more consistently than the standard trap. This may increase the chance of a proper strike with squirrels or raccoons, or other small or flexible animals that might pull back if there's a slight gap between the jaws. Magnum versions are very strong—a #220 Magnum body-gripping trap could break bones—so be very careful when setting the trap. Consider using setting tools and safety devices.
To set a body-gripping trap, you must compress the spring until its tips nearly meet at the rotating point of the jaws. Then hold both jaws open and fit the dog (a.k.a. the "trigger hook"), which is notched, into the notch located on the trigger. Once securely in place, the dog holds the jaws open. In its correct position, the jaws of the trap close on the top and bottom of the animal. Stabilize the trap to keep it in this top-to-bottom strike position, and to ensure that it can't easily be knocked over. Anchor the trap, too. (These traps are lightweight enough to be carried off by predators attracted by the captured animal.) In New York, the jaw spread of a body-gripping trap set on land cannot be greater than 5 3/4 inches (the jaw spread is the distance between the two jaws when the trap is set).
Some models of body-gripping traps, usually those with two springs, have safety hooks that hold one spring while you're setting the other. If you use a safety hook, remember to release it when you're done setting the trap, so the trap can fire.
When an animal passes through the jaws of the trap, it moves the trigger, which dislodges the dog from its notch and springs the trap, closing the jaws around the animal's neck or chest. Ideally, this trap catches the animal directly behind the head, snapping the part of the spine that's in the upper third of the neck (called the "cervical spine" area). A proper hit provides a quick death.
If you are trapping raccoons, skunks, squirrels, or woodchucks, modify the trigger to help to ensure a top-to-bottom strike (which is more humane) and prevent the animal from refusing to enter the trap. These species don't like to have anything brush against their eyes or whiskers, so separate the trigger and center it on the bottom of the trap.
As with all lethal techniques, care is needed to make sure that only the intended nuisance animals are caught. Body-gripping traps are often set in front of the animal's entrance hole because the animal must pass through the jaws of the trap to be captured. This way, only an animal entering or leaving the hole will be caught. If necessary, guide the animal into the trap. Use hardware cloth to reduce the size of the entry hole (shown in the photo) or to block escape routes.
This tool often provides the quickest way to remove a raccoon or squirrel from an attic. Another advantage is that non-target animals are not nearly as likely to be on the roof as they are on the ground. But this trap is not appropriate for all settings.
Use extra caution if you're setting a body-gripping trap on the ground, because of the risk to people, pets, and other wildlife. You can modify your technique and your equipment to minimize these risks. Here are some suggestions.
Cover the trap and burrow entrance
Let's say you've been unsuccessful trying to catch a woodchuck in a cage trap, or you need to trap many woodchucks. A body-gripping trap, if used cautiously, may be the right tool. Dig out the opening to the woodchuck's den a bit, so you can set the body-gripping trap in the burrow's entrance. The trap should be attached to a stake in the ground. Cover the burrow entrance and the trap with a large, loosely attached piece of hardware cloth, or with a box. When the woodchuck leaves its den, it will spring the trap, but an animal poking its head into the burrow entrance wouldn't.
Place the trap in a container (a vertical cubby set, deep-notch box, or bucket with small hole)
Three views of a body-gripping trap placed in a vertical cubby set. Above, left: The vertical cubby is attached to the tree at about five inches off the ground, to make sure that a dog can't reach up into the box and spring the trap. Right: In this set, the trap was held in place by friction, so when it sprung, the trap fell out of the box. You can anchor the trap so it will remain in the cubby after it's sprung, too. Bottom: Bait is placed on a shelf near the top of the box. Notice the body-gripping trap in its set position. You can see the trigger and jaws within the box, and the spring sticking out to the left.
One way to lower the risk of catching an unintended species is to use a vertical "cubby" set, shown in the photographs. This is a baited box that's open on one end, with the trap set well inside, usually held in place by friction between the coilsprings and the narrow notch in the box. You must use a model with two coilsprings, because one with a single spring won't stay in place. Make sure the open bottom of the box is no more than five inches off the ground. If a dog investigates, it may be hit on the nose, but it's unlikely that the trap would capture the dog. Cats cannot easily enter a vertical cubby set.
The deep-notch box is an alternative to the vertical cubby set. It's set horizontally on the ground. If you're using a #220 body-gripping trap, the notches should be 8" deep. The trap is placed in the midpoint of the notches, which hold the trap in place. Make sure the trap is securely anchored. Center the trigger on the top of the trap. Bait should be placed deep inside the box, at least 6" behind the trap. The top of the deep-notch box is blocked with a piece of wood (see photo). By restricting the size of the opening, you reduce the risk that a dog will spring the trap. The opening of a deep-notch box should be no more than 7" high.
By restricting the size of the opening, you reduce the risk that a dog will spring the trap. The opening of a deep-notch box should be no more than 7" high.
Although the vertical cubby set and the deep-notch box work on the same idea, and are interchangeable, they have different strengths. The vertical cubby is less likely to attract cats (unless you've used the wrong bait) and is even more dog-proof than the deep-notch box. Sometimes, a raccoon will avoid a vertical cubby but investigate a deep-notch box. Some NWCOs prefer one design over the other, as well.
Another option is to place the body-gripping trap inside a plastic bucket that has a restricted opening. The bucket can be round or square, as long as it has a lid. An opening no larger than 7" is cut into the lid, slightly off-center. It works like a deep-notch box, only it's made from plastic instead of wood. Have some extra lids prepared, in case one is damaged or lost.
Use baits that selectively attract the nuisance animal
Both marshmallows and sardines will attract raccoons, but marshmallows won't entice cats, so that's a safer bait to choose if you must trap in an area where there are free-roaming cats. Mice will be attracted by many baits that are of varying appeal to other species, but you could avoid using bait entirely. Tie a cotton ball to the trigger instead. That's an attractive bit of nest material to a mouse, but cotton is of no interest to many other species. Whenever possible, use baits and lures that will attract only the nuisance animals.
Use a trap with a one-way trigger
The one-way trigger rests against the bottom jaws of the trap and only moves freely in one direction. In this illustration, the animal would have to move from left to right to lift the trigger and spring the trap. An animal coming from the other direction might bump the trigger, but it's not likely to lift it high enough to spring the trap.
Compare the trap with the one-way trigger to the standard model shown below it. See how that trigger swings freely? It can spring the trap regardless of which way the animal approaches. That means it can catch an animal on its way out of its den, which is what you want—but it might also accidentally capture an animal that stopped to investigate. In some cases, that might be the wrong animal.
There are commercial traps with one-way triggers, but you can modify an existing trap, too. For example, you can add a 220-wire trigger to a #120 body-gripping trap.
Lethal techniques: Other lethal traps
Mouse and rat snap-back traps. The familiar mouse trap is a form of body-gripping trap. And yes, people have "built a better mouse trap." Several, in fact (see the illustrations on the next page).
Your trapping strategy will vary depending on whether you're trapping mice, rats, or other small mammals. See the species accounts for mice and Norway rats in Appendix B for information about the number of traps to use and how to place them effectively.
Left: Victor Quick Kill Trap. The bait cover, which is actually the trap's trigger, is shown in black (with the V). When the lid is lifted, the strike bar lowers. Right: a clothespin design.
If you're trapping mice or rats, you'll need to use many traps, so you may want a model that's easy to set. There are many options besides the traditional mouse trap, which can be cumbersome. Snap-back traps with expanded triggers, and the "clothespin" design are much easier to set than the traditional mouse trap. The Quick Kill Mouse Trap made by Victor has a lid over the bait cup. Only animals that are motivated to seek the bait will lift that lid—and that's what triggers the trap. This means that an animal can accidentally step on the lid without setting off the trap. There's another advantage to this design. The bait cup is located to position the mouse in the perfect strike position. So this trap is both more selective and more effective than the traditional mouse trap. It also has a safety catch and will not fire if it's picked up.
Mole traps, another form of body-gripping trap, come in several designs. Some spear the moles with a harpoon, others have scissor-like jaws. They are all set underground in the moles' tunnels. The key to successful mole trapping is to identify active tunnels. Look for dead grass or soft spots in the lawn. Prepare the site and set the trap according to the instructions given for the particular trap design. If there is no activity after a few days, move the trap. If moles are active near the trap, but you're not catching them, either add more traps, or switch to another type of trap.
Foothold traps can be used as lethal traps, as well. This is generally limited to a submersion set used to capture beaver or muskrat.
Glue boards are just what they sound like: a layer of long-lasting adhesive spread over a surface, usually cardboard or plastic. Small animals get stuck in the adhesive. Although some call the glue board a live trap, it's not often used that way. In fact, some biologists believe that you cannot remove the animal from the trap unharmed, because the oil that is used to loosen the glue may harm the animal. In practice, animals are frequently left to die on glue boards. Glue boards are not recommended as a general-use tool. They may be needed to deal with some severe infestations of mice or rats. Snap-back traps are often as effective as glue boards and are more humane, though setting them does take more effort. If you use glue boards, check them frequently and use a best practice to humanely kill the mice or rats.
Advantages of lethal trapping
- when it works right, lethal traps are one of the fastest and most humane killing methods
- same piece of equipment can be used to capture and kill animal, so there's less handling involved
- equipment is easy to get and reasonably priced
- it's easy to transport equipment
- equipment is lightweight and compact, especially when compared to cage traps
Disadvantages of lethal trapping
- can capture and kill nontarget animals
- can hurt people
- may require additional tools to set the trap
- misfire could result in injury to animal
- site often needs preparation, so it may take longer to set trap
Lethal techniques - Shooting
Firearms includes pistols, shotguns, rifles, hand guns, and air rifles (high-end pellet guns). This technique is appropriate for use with medium to large mammals (squirrel size and larger), birds, and reptiles. Obviously, shooting requires training and skill. There are safety concerns and legal restrictions to consider, too. For proper training in the use of firearms, attend the DEC Hunter Education course or a training course sponsored by the National Rifle Association (NRA).
If an animal is restrained, shooting may be one of the fastest and most practical ways to humanely kill a wild animal.
General tips | Guidelines for shooting mammals | Guidelines for shooting birds | Advantages and disadvantages of shooting
General tips for the use of shooting
- Take the time you need to take the best shot.
- The type of firearm you choose and the ammunition should be matched to the size and species of the animal.
- In most cases, small-caliber, low-energy projectiles are best. A .22 caliber rifle is adequate for most small mammals. Air rifles may be used on squirrels and birds. Among the most effective types of ammunition are hollow point bullets or low velocity .22 rimfire cartridges, such as shorts or CB caps, which are also quieter.
- Pay attention to the surface underneath, around, and behind the animal. Could a bullet ricochet? Bullets are less likely to ricochet off softer surfaces such as dirt or grass than off hard surfaces like concrete, asphalt, or rocks, or water.
- You must follow both state and local firearms regulations.
- Make sure the situation is safe. If a crowd has gathered, disperse them before you shoot the animal, or take the animal elsewhere.
- Some species continue to move after they've been shot, such as squirrels, birds, raccoons, opossums, and woodchucks. This is a reflex but can be difficult to explain to someone who's watching. A good reason to be discreet.
Guidelines for shooting mammals
If you need to do a rabies test, don't shoot the animal in the head. You might destroy so much brain tissue that the lab wouldn't be able to do the test, and you could spray potentially contaminated brain tissue into the air, which might expose you to the virus if the tissue came into contact with your eyes, mouth, or nose. (Rabies virus by itself is not airborne.) Instead, aim for the heart and lungs. The heart/lung target may also be a better option if dealing with a free-roaming animal, such as a deer.
Target areas for the brain or heart/lung shots shown on a fox (illustration not to scale). The target areas are the same for most mammals, with the exception of the opossum.Target areas for the brain or heart/lungs shots shown on a opossum (illustration not to scale). Opossums have very small brains housed in a reasonably large skull. This means the target area- the brain - is actually much smaller than you'd imagine, just from looking at the size of the animal's head. Their brain is about the size of a pea.Opossums also have a very big crest that runs down the center of their skulls, called the "sagittal crest". It's very strong to deflect bullets. Unfortunately,, if you try to aim slightly off to the left or right to avoid hitting the crest, you miss the brain entirely. A side target might be a little easier. Imagine a line drawn between the eye and the ear, and aim closer to the base of the ear.
What if you shot an animal in the head, and later learned that a rabies test is needed? Don't panic. Submit the specimen. In many cases, the specimen will be adequate. What about that worst-case scenario, when it's not possible to do an accurate rabies test? Then, as a precaution, the exposed person or animal would receive the post-exposure rabies vaccinations. That's not fun, and there's a limited supply of one of the drugs that's given as part of this series, so don't be cavalier about the quality of the specimens you submit for rabies tests.
Although the head shot (aiming for the brain) is often considered faster and more humane than the heart/lung shot, this isn't necessarily true. Please note that few people would be able to ensure a proper head shot at anything except close range.
To properly target either the brain or the heart/lungs, you must think in three dimensions. Without proper aim, the bullet could deflect off the skull. For the brain shot, the barrel of the firearm should be a few inches from the head. Ideally, aim so the bullet will travel through the brain and spine and lodge in the animal's body. If the animal's head is turned so you don't have the right target, you may be able to distract it and get it to move its head by tossing a rock.
Guidelines for shooting birds (unprotected species)
House sparrows, starlings, and pigeons can become trapped within large buildings such as malls, warehouses, and airport terminals. These structures often have food, water, and even nesting resources that allow the birds to survive. One of the most effective ways to remove a small number of birds from a large building is with an air rifle. Choose a higher end model with a scope for improved accuracy and performance. Most often, you'll shoot the birds when the building is closed to the public. (Although pellet guns are not as powerful as gunpowder firearms, there are still risks to human safety, and to property.) Learn where the birds roost, then choose a position that will provide you with good shots. The building management may have a lift that will provide you with an elevated platform.
Advantages of shooting
- shooting is one of the fastest and most humane methods for killing wildlife
- it will work with many different species, under many conditions
- minimizes the handling of a live animal
Disadvantages of shooting
- may splatter brain tissue, saliva, or blood, which could expose someone to wildlife diseases
- may interfere with the collection of the tissue sample needed for the rabies test
- cannot be done everywhere. There are legal restrictions and safety concerns that limit its use
- requires skill and proper equipment
- can be dangerous to people and other species
Lethal techniques: Carbon dioxide chamber
The technique is fairly simple: the animal is placed in an enclosed space into which carbon dioxide gas is added at a controlled rate. When the animal breathes this gas, it quickly loses consciousness and then dies. The entire process takes about five minutes.
How does it work?
Carbon dioxide (CO2) is a colorless, odorless gas. It's called an "inhalant agent" because the animal must breathe it in. CO2 affects the nervous system, the lungs, and the heart.
Can I use CO2 on any species?
Carbon dioxide chambers work well to humanely kill birds, rodents, and most small mammals. But you may encounter problems if you try this technique on animals that are old, very young (less than 2 weeks old), weak, or sick with a respiratory disease, because they're often resistant to the effects of carbon dioxide. If possible, choose another technique to humanely kill animals that breathe slowly (such as reptiles or amphibians) or are very good at holding their breath (such as beaver and diving birds). Under these circumstances, CO2 might take too long to be considered a best practice.
Commercial carbon dioxide chambers are often made of metal and have windows for monitoring the animal, but the chamber can be made of many materials, such as plywood or plastic. Coolers, garbage cans, and other containers have been converted into chambers. The best chambers are clear or have windows so you can monitor the animal, and are also easy to clean and transport.
You may want to have several chambers of different sizes and designs, and a portable model. For example, bats can be more humanely killed in a small chamber that fills faster. A small, clear plastic container with two holes drilled into it (one for the tube feeding the gas, and a vent hole) would work well.
One NWCO has rigged a garbage container on wheels to serve as both an enclosed trap and carbon dioxide chamber. He sets a cage trap within the chamber, then, after capturing the animal, wheels the can to a place where he can safely and discreetly attach the carbon dioxide tank and kill the animal. This combination of a trap within the CO2 chamber also offers a safety advantage, because there is no handling of the animal. Consider such an approach, especially when dealing with sick, rabies suspect, or highly aggressive animals.
There may be a market niche for those willing to provide on-site wildlife euthanasia services, especially in areas where other techniques that are generally accepted by the public, such as shooting, aren't legal or practical. With care, carbon dioxide chambers can be safely transported.
Equipment needed - Homemade CO2 chamber
- Many commercial coolers come with a drain hole at the bottom. Attach the hose to the drain hole. If your model lacks a drain hole, you can drill it out. To add a window to your chamber, drill through the cooler using a jigsaw. Cut a piece of plexiglass to fit, then attach to the cooler using epoxy.
- chamber that's twice as big as the animal
- tank of carbon dioxide gas (available in several sizes such as 6 lb., 20 lb., 50 lb., and 60 lb. If you don't need to lug it around, a larger tank might be cheaper to refill.)
- hose or rubber tubing
- flow regulator
- commercial carbon dioxide chambers are available in different designs
- check with welding suppliers; you may be able to rent some of this equipment
- Choose a chamber that can hold a large cage trap so you don't have to handle the animal. This is safer for you and less stressful for the animal.
- The animal should be able to sit and rest comfortably within the chamber.
- If the chamber is too tall, or if the vent hole is too low, the animal may be able to lift its head above the level of CO2 gas, which would make the process take longer.
- The chamber is NOT supposed to be airtight! Air must be able to escape to leave room for the carbon dioxide. Carbon dioxide is heavier than air, so it fills from the bottom up (like filling a glass of water). A vent hole near the top of the chamber or a loosely-fitted lid will let out the air but not the CO2. The vent hole will also prevent pressure buildup.
- Have a spare tank of CO2 ready.
- Don't mess around with dry ice, fire extinguishers, car exhaust, or antacids as sources of carbon dioxide. They will not work reliably.
- Always work in a well-ventilated space to minimize your exposure to the CO2, which can be dangerous to people, too.
- Attach the hose from the CO2 tank to the bottom of the chamber.
- Ideally, carbon dioxide should enter the chamber at a rate that displaces 20% of the oxygen each minute (more on this later).
- Should you fill the chamber with CO2 before putting the animal in it? (This is called "precharging.") Some experts say "yes," others "no." Precharging will speed up the process but many animals will react violently to high concentrations of CO2 if they're awake. It's less stressful to expose the animal to the gas at a carefully controlled rate. Right now, we say "no," but watch for more research.
- Even if you have a commercial carbon dioxide chamber, you may want to consider building your own mobile unit.
- The chamber should be cleaned and aired out between uses. (A good reason to have more than one chamber.)
Carbon dioxide chamber - Using a CO2 chamber, step-by-step
1. Calculate the optimal CO2 flow for your chamber. This depends on the chamber's size. Your math has to be done in the same units used by the flow regulator. Most are either calibrated in cubic feet/hour or liters/minute. If your flow regulator is calibrated to measure the amount of gas flow in "cubic feet/hour," here's how to convert your measurements to match:
- Measure the chamber's size (for this example, say it's 14" × 14" × 34")
- Convert this measurement into cubic feet first, divide each measurement by 12
- 14 ÷ 12 = 1.2
- 14 ÷ 12 = 1.2
- 34 ÷ 12 = 2.8
- then multiply the three measurements
- 1.2 × 1.2 × 2.8 = 4 cu. ft.
- Divide the chamber's size (in cubic feet) by the accepted amount of time (5 minutes, or .08 hours) to determine the flow rate: 4 ÷ 0.08 = 50 cu. ft./hour. So in this example, the ideal flow rate for this chamber is 50 cubic feet/hour.
2. Place the animal into the chamber. If it's in a trap, you can put the entire trap into the chamber.
3. Turn on the carbon dioxide gas until the flow regulator shows the flow rate you've just calculated.
4. Watch the animal. At first, the animal may move about or seem excitable. That's a normal reaction that often happens right before the animal loses consciousness. If you see signs of extreme distress (excessive vocalizations, head shaking, fierce sneezing) turn down the flow rate. Later on, when the animal's totally unconscious, it may still continue to move. That's a reflex, not a sign of pain. Some NWCOs find that skunks react better to a slower flow rate.
5. Wait a few minutes after the animal's stopped moving and then turn off the gas. You can leave the animal in the chamber a little longer, if you'd like. It's important to confirm that the animal is dead because if it isn't and you expose it to air, it could revive. How can you tell? Touch a long stick to its eyeball. If it's dead, it won't blink. Or hang a string in front of its nose (just keep your hands away from the animal's teeth). If it's dead, the string will stay still, because there won't be any breath to move it.
6. If the animal's not dead, or if you're not sure, put it back in the chamber and repeat the process, or use another method.
Advantages of carbon dioxide chambers
- it's been well-studied and has proved highly reliable
- one of the most practical techniques for NWCOs
- does not interfere with rabies testing
- equipment is easy to get and reasonably priced, or can be made easily
- can be done on-site
- poses few hazards to people
- doesn't require special skills, strength, or additional permits
- some of your customers may prefer this method, so there may be marketing advantages to its use
Disadvantages of carbon dioxide chambers
- may not work as well with burrowing or diving mammals; reptiles; amphibians; animals that are old or very young (less than 2 weeks old); weak animals; and those that are sick with a respiratory disease
- may be slower than some of the other humane killing methods
- may cause distress at first
- equipment is a bit bulkier, and requires cleaning and airing between uses
- you have to do a little math
Lethal techniques: Cervical dislocation
This method is commonly referred to as "breaking the neck" but would more accurately be described as "snapping the spine." The goal is to quickly separate the spinal cord from the brain to provide a fast and painless death. The separation must take place at the base of the brain or within the upper third of the neck (the cervical spine area).
This method requires skill, practice, and strength, especially with the larger animals, which have thicker, stronger necks. NWCOs unfamiliar with this technique should receive training and practice on dead animals before attempting this on a live animal.
Cervical dislocation is used primarily for small to medium-sized birds (duck sized or smaller) and small mammals, such as mice and rabbits. Be cautious if working with a mammal, especially a rabies vector species (it's safest to use a different method for them). This technique brings your hands into direct contact with the animal's head near its mouth. Remember that no glove can provide 100% guaranteed protection.
To snap the spine of a pigeon or duck-sized bird, grasp the base of the bird's skull in one hand and its body (usually at the base of the neck) in the other hand. Pull hard and fast—twist your hands in opposite directions.
Another cervical dislocation technique for birds uses pliers or vise grips.
For smaller birds (up to 11 oz., about the weight of a pigeon), hold the bird in one hand, and a pair of needle-nose pliers in the other. Place the open pliers over the bird's neck vertebrae (in the cervical spine area). Slide the pliers up the neck until they contact the head and are directly over the first and second vertebra in the top of the neck, which support the skull (the atlas and axis vertebra). Then close the pliers firmly and hold for 2–5 seconds.
For larger birds (12 oz.–3 lbs., the upper limit is about the weight of a gull): Hold the bird in one hand, and a pair of square-jawed vise grips in the other. Adjust the vise grips so its jaws will slide over the bird's neck but not over its head. Then slide the vise grips up to the base of the bird's head. With your other hand, pull the bird's body quickly, to snap its spine (separating the cervical vertebrae from the skull).
To snap the spine of a small mammal or larger bird, put it on a hard, flat surface. Hold a strong stick or metal rod firmly against the base of the animal's skull. Pull its body away from its head in a single, steady motion. Keep the stick in place, then bend the body over the head.
Advantages of cervical dislocation:
- it's one of the fastest humane killing techniques
- no equipment necessary
- can be done discreetly in the field
- if done correctly, it's not bloody
Disadvantages of cervical dislocation:
- brings your hands into direct contact with the animal's head, which, if dealing with mammals, increases your risk of exposure to rabies
- this technique doesn't look as good as others and may disturb onlookers. Animals often keep moving for several seconds or even minutes after death. That's not a sign of pain; it's a reflex.
- requires skill, speed, and strength
- best restricted to small mammals (excluding the rabies vector species) and bird
Lethal techniques: Stunning
Stunning may be used for two different purposes: it may be intended to make the animal unconscious so another killing method may be used safely, or it may be intended as a primary killing method, in which case it's usually referred to as a "lethal blow."
A lethal blow is a quick, very forceful blow to the head that is meant to kill the animal. It is appropriate for small animals, such as birds, rabbits, and small mammals (mice to squirrel-size). Work on a hard surface. The animal must be properly restrained so you can deliver the blow to the right location, which is the back of the head, unless using a special tool called a "penetrating captive bolt pistol."
The penetrating captive bolt pistol is a particularly helpful although expensive tool, which is often used on livestock. Powered by gunpowder charges or compressed air, this device forces a metal rod through the animal's skull into its brain. Proper placement of the bolt on the forehead is crucial, so the animal must be securely restrained. And make sure that no one is within the "firing range, " which is the length of the bolt, because they could be hurt. (One thing you must watch out for: make sure you have a penetrating captive bolt pistol. There are captive bolt pistols that don't penetrate the brain. They just stun the animal.)
All of the cautions that apply to cervical dislocation also apply to the use of a lethal blow, and to stunning. Although a lethal blow by itself may humanely kill the animal, it's best to use a second method to be absolutely sure. Sometimes, NWCOs will stun an animal so they can more effectively use the killing method they've chosen. For example, a fox that's been captured using a catchpole may be stunned so it can be safely handled and placed in a carbon dioxide chamber.
Stunning is a less forceful blow delivered to the center of the head. The animal must be properly restrained to ensure the correct positioning of the blow. Once the animal is stunned unconscious, you can choose among several techniques to kill it.
Stunning and use of carbon dioxide chamber: if an animal has been captured using one of the direct capture techniques, such as with a catchpole, it may be stunned to allow the NWCO to transfer it to the chamber safely.
Stunning and shooting: if an animal is moving around too much to allow for a proper target, you can stun it into unconsciousness, and then orient it for the best shot. Or perhaps you need to move the animal to a place where it's safer to shoot it.
Stunning and cervical dislocation: This combination may be used on duck-sized birds, to gain a little more time to properly snap the spine.
Stunning and decapitation: "Decapitation" means the head is quickly cut from the body. This method works like cervical dislocation. The goal is to quickly separate the spinal cord from the brain to provide a fast and humane death. Decapitation is used primarily for birds that are too large for cervical dislocation, such as geese, and sometimes for snakes. A recently killed snake may bite by reflex, so don't handle its head. Use a heavy knife, ax, hatchet, or bolt cutters to cut the spine of a bird at the base of the head. A long-handled shovel or hoe can be used for a snake. The same uncontrolled movement that is seen after cervical dislocation will follow decapitation. A goose might flop around for up to two minutes. The same safety precautions that apply to cervical dislocation should be considered when using stunning and decapitation. This method is messy and forceful. Blood and brain tissue could be splattered. If dealing with a mammal, the splattering of contaminated brain tissue or saliva could expose you to the rabies virus. (Rabies is not a blood-borne disease.)
Stunning and bleeding out (or "exsanguination"): the major blood vessels, usually those in the neck, are cut to rapidly drain blood from the body. This ensures death but is a messy and bloody technique.
Advantages of these combination methods:
- stunning the animal first ensures that it is unconscious
- may make a situation safer for the NWCO and other people
- may allow the NWCO to use a preferred killing method, such as shooting or a CO2 chamber, in a situation in which that method would otherwise be difficult to use
- when properly done, these are fast and humane techniques that quickly break the brain-body connection
- no specialized equipment necessary for some of the combined methods
Disadvantages of these combination methods:
- may bring your hands into direct contact with the animal's head, which, if dealing with mammals, increases your risk of exposure to rabies
- some of these techniques may disturb onlookers. Some are bloody. Animals often keep twitching for several seconds, or even minutes, after death. That's not a sign of pain; it's a reflex
- will likely have more of a mess to clean up (consider working over a tarp to contain the mess)
- may require skill, speed, and strength
Lethal techniques: Chest compression
The goal of this method is to quickly stop the heart. This technique may be applied to small to medium-sized birds such as starlings or pigeons (but not diving birds); and small mammals (up to about 15 lbs., which includes animals the size of a young raccoon, or fox). Don't attempt this technique on a larger mammal because you'd be unlikely to accomplish it in a timely and humane fashion. This is not a preferred technique for mammals ranging closer to the fifteen-pound limit, but it is acceptable, and may be your best option in some cases.
Bring your thumb and forefinger of one hand under the bird's wing from the back, and hold them against the bird's ribs. Place the forefinger of your other hand against the bird's breastbone ("sternum") just below the spot where the "wishbone" forks. Squeeze your fingers together forcefully and hold the pressure to stop the heart.
First, stun the animal between the eyes to make it unconscious. Then strike it again at the back of the head, which should be a lethal blow. Immobilize the animal by standing on its neck with one of your feet. Locate its heart, then compress the heart by standing on it.
Advantages of chest compression:
- when properly done, this is a fast technique
- no specialized equipment necessary
- may be one of the few practical options available in some situations
Disadvantages of chest compression:
- may disturb onlookers
- requires skill, speed, and strength
Lethal techniques: Barbiturates
These drugs, such as sodium pentobarbital, sedate and can kill animals by interfering with the central nervous system. Barbiturates are the drugs vets use to "put animals to sleep." And that's not a bad description of what it looks like, because they usually work smoothly. Animals must be well restrained for the injection.
This isn't a practical method for most NWCOs because they don't have access to the drugs. Even DEC wildlife biologists and university researchers have difficulty securing barbiturates. These are dangerous drugs that can kill people, so their use is heavily regulated by the federal government. Only trained personnel registered with the U.S. Drug Enforcement Agency (such as veterinarians) have access to barbiturates. You'd need a license, and in New York, also a certificate of need from the Department of Health to allow you to use hypodermic needles. There are strict security issues. And lots and lots of paperwork.
There are two possible ways that a NWCO might be able to use this method. First, you could transport the nuisance animal to a veterinary clinic, so the vet can inject it with barbiturates. But is that a great choice? Consider how the capture and transportation could stress the animal—would this cancel out the advantages of the use of barbiturates? Would your customers pay fairly for this service?
In rare cases, a NWCO partners with a veterinarian who agrees to supervise and take responsibility for the NWCO's use of barbiturates in the field. This is a significant liability risk for the vet, so few are willing or able to offer this assistance.
There are many practical limitations, because the NWCO must go to the vet's office before going out on each job that requires the use of the drugs. The vet would give you the amount needed to kill that animal. Could you fit this into your schedule in any reasonable way?
You must also consider how you'd dispose of the carcass, because barbiturates can persist in the animal's body. A predator or scavenger that feeds on an animal that was killed by barbiturates might also die.
Advantages of barbiturates:
- one of the fastest and most reliable humane killing methods for small animals
- a gentler process that causes minimal distress
- because barbiturates sedate animals, they may make the handling of a dangerous animal safer
- Although the unconscious animal may gasp right before death, the technique minimizes the thrashing sometimes seen with other killing methods
Disadvantages of barbiturates:
- these drugs are not available to most NWCOs
- these drugs can kill people and other animals
- you'd need to get close enough to the animal to use a dart gun or hypodermic and that may not be possible or safe
- requires special training and additional permit
- the drugs may persist in the carcass and affect any animal that feeds upon it
Lethal techniques: Pesticides
You'd need another license and would receive separate training in the safe and effective use of pesticides, so we won't even try to summarize it here. There are relatively few pesticides available for the control of wildlife. Most are rodenticides, targeting such rodents as mice and the Norway rat. Fumigants and gas cartridges are registered in New York State to kill Norway rats, woodchucks, chipmunks, voles, and moles in their burrows. There are products, such as Avitrol®, registered for use on birds. Some details are shared in Appendix B. Remember, pesticide regulations and registrations change frequently, so always check for current information.
Clean-up and disposal of dead animals, contaminated materials
Most NWCOs do a certain amount of cleaning as part of their service. If the site presents a formidable mess, some NWCOs contract for cleaning separately while others recommend a service. Whether you do a little or a lot of cleaning on site, you'll still need to clean your gear and your truck. Here's a quick review. For more details, see chapter four.
- Clean and disinfect your equipment with a disinfectant or a 10% chlorine bleach solution—one part bleach to nine parts water. Mix up a new batch each day. Never mix bleach and ammonia!—that forms a toxic gas. For the same reason, don't apply bleach to bird droppings, which also contain ammonia.
- Remember, if you're working around bird, bat, or rodent droppings or nest materials, don't stir up dust. Wear the proper safety gear. Use disinfectant to wet down anything that might have been contaminated, including any dead animals. Wipe up with a damp towel or sponge, or use a commercial, heavy-duty vacuum.
- Cleaning up after raccoons is a bit trickier. The eggs of the parasite that causes raccoon roundworm are resistant to disinfectants. Areas of soil or concrete that have been contaminated can be flamed thoroughly, using a handheld propane torch (a weed burner). Turn the soil over, then flame it; repeat this process a few times. Metal traps can also be flamed; or you could opt to clean them with boiling water and bleach. To decontaminate a fireplace, woodstove, and chimney, build a roaring fire. Contaminated materials that can't withstand burning should be cleaned with boiling water and bleach. This is a good option for wooden decks, porches, and contaminated clothing.
- If you're dealing with a mangy animal, clean anything that may have picked up mites, such as your clothing, equipment, or truck. The bleach solution is one option, or you can freeze objects, which will kill any mites.
- To refresh your memory for safety protocols, here are the diseases you're more likely to encounter when working with:
- Birds: histoplasmosis
- Bats: histoplasmosis, rabies
- Rodents: hantavirus (squirrels often get mange)
- Raccoons: rabies, raccoon roundworm, distemper
- All of these species attract a variety of parasites, too. And although they don't catch it as often, woodchucks, squirrels, and birds may suffer from raccoon roundworm. Any mammal can be infected with rabies.
- Carcasses and other potentially contaminated materials (gloves, protective clothing, nesting materials) must be disposed of properly, because they can also spread diseases. In New York State, the Health Department may give you specific disposal instructions for animal carcasses, which you must follow. Otherwise, the animals and other materials may be buried, burned, or sent to a landfill.
That takes care of health concerns, but most people won't consider a place clean if it still reeks. Some NWCOs simply refer customers to commercial cleaning services. There are many commercial deodorizers that will eliminate wildlife odors. You'll find details in the skunk account.
One expensive machine, an ozone generator, has been marketed to NWCOs as a way to clean or purify air. Here's what the EPA has to say about that. "Often the vendors of ozone generators make statements and distribute material that lead the public to believe that these devices are always safe and effective in controlling indoor air pollution. For almost a century, health professionals have refuted these claims... Ozone can cause health problems at high concentrations." (the full report).