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Nuisance wildlife management

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Deer eating tomato plant

Nuisance wildlife management is the term given to the process of selective removal of problem individuals or populations of specific species of wildlife. Other terms for the field include wildlife damage management, wildlife control, and animal damage control to name a few. Some species of wildlife may become habituated to man's presence, causing property damage or risking transfer of disease to humans or pets (zoonosis). Many wildlife species coexist with humans very successfully, such as commensal rodents which have become more or less dependent on humans.

Characteristics of nuisance species

Deer-damaged tomato plant has been stripped of developing fruit

Typically, species that are most likely to be considered a nuisance by humans have the following characteristics. First, they are adaptable to fragmented habitat. Animals such as Canada geese (Branta canadensis) love ponds with low sloping banks leading to lush green grass. Humans love this sort of landscaping too, so it is not surprising that Canada geese have thrived (not to mention the decline in hunting).

Second, these animals are not tied to eating a specific type of food. For example, lynx do not thrive in human impacted environments because they rely so heavily on snowshoe hares. In contrast, raccoons have been very successful in urban landscapes because they can live in attics, chimneys, and even sewers, and can sustain themselves with food gained from trashcans and discarded litter.

Third, successful animals must not pose an obvious significant risk to human health and safety. Animals perceived as grave threats will incur the extreme ire of humans and be under constant threat of humans seeking to eliminate them.

Finally, successful animals in humanized landscapes are often perceived as "cute", at least until they become so numerous that their preferential status becomes diminished. Many wildlife species have the potential of becoming a "nuisance" species, and whether or not a species is regarded as a pest can be directly correlated with the degree to which that animal can be tolerated by humans. For many people, tree squirrels feeding in their yards or gardens are not a problem; a neighbor may feel that these same squirrels nesting in the attic of their house are a nuisance and a fire hazard, due to their habit of gnawing on electrical cables.

Common nuisance species

Common wildlife pests include armadillos, skunks, boars, foxes, squirrels, snakes, rats, groundhogs, beavers, opossums, raccoons, bats, moles, deer, mice, coyotes, bears, ravens, seagulls, woodpeckers and pigeons. Some of these species are protected by state or federal regulations, such as bears, ravens, bats, deer, woodpeckers, and coyotes, and a permit may be required to control some species.

Wildlife are usually only pests in certain situations, such as when their numbers become "excessive" in a particular area. Human-induced changes in the environment will often result in increased numbers of a species. For example, piles of scrap building material make excellent sites where rodents can nest. Food left out for household pets is often equally attractive to some wildlife species. In these situations, the wildlife have suitable food and habitat and may become a nuisance.

Controlling wildlife damage

Raccoon on a roof.

The primary objective of any control program should be to reduce damage in a practical, humane and environmentally acceptable manner. Wildlife managers and wildlife control operators (WCOs) use control methods based on the habits and biology of the animals causing damage. By using methods matched to the nuisance species, control efforts will be more effective and will serve to maximize safety to the environment, humans and other animals.

A key to controlling wildlife damage is prompt and accurate determination of which animal is causing the damage. Even someone with no training or experience can sometimes identify the pest by thoroughly examining the damaged area. Because feeding indications of many wildlife species are similar, other signs – such as droppings, tracks, burrows, nests or food caches – are usually needed to make a positive species identification.

After the wildlife pest is identified, control methods can be chosen appropriate to the animal species involved. Improper control methods may harm but not kill the animal, causing it to become leery of those and other methods in the future. For example, using traps and poison baits improperly or in the wrong situation may teach the animal that the control method is harmful. This may make the animal difficult to control later, even with the correct method.

Four steps lead to a successful nuisance wildlife control program:
  • Correctly identify the species causing the problem.
  • Alter the habitat, if possible, to make the area less attractive to the wildlife pest.
  • Use a control method appropriate to the location, time of year, and other environmental conditions.
  • Monitor the site for re-infestation in order to determine if additional control is necessary.

Control methods

The most commonly used methods for controlling nuisance wildlife around homes and gardens include exclusion, habitat modification, repellents, toxic baits, glue boards, traps and frightening. Wildlife control involves human risks both from possible injury to person and property, but also from zoonotic disease.

Exclusion

Physically excluding an offending animal from the area being damaged or disturbed is often the best and most permanent way to control the problem. Depending upon size of the area to be protected, this control method can range from inexpensive to prohibitively costly.

For example, damage by birds or rabbits to ornamental shrubs or garden plants can be reduced inexpensively by placing bird netting over the plants to keep the pests away. On the other hand, fencing out deer from a lawn or garden can be more costly. Materials needed for exclusion will depend upon the species causing the problem. Large mammals can be excluded with woven wire fences, poly-tape fences, and electric fences; but many communities forbid the use of electric fencing in their jurisdictions. Small mammals and some birds can be excluded with netting, tarp, hardware cloth or any other suitable material; nets come in different weave sizes suitable for different animals to be excluded.

However, exclusion can interfere with the natural movement of wildlife, particularly when exclusion covers large areas of land.

Habitat modification

Modifying an animal’s habitat often provides lasting and cost-effective relief from damage caused by nuisance wildlife. Habitat modification is effective because it limits access to one or more of the requirements for life – food, water or shelter. However, habitat modification, while limiting nuisance wildlife, may also limit desirable species such as songbirds as well.

Rodent- or bat-proofing buildings by sealing cracks and holes prevents these animals from gaining access to suitable habitats where they are not welcome. Storing seed and pet food in tightly closed containers, controlling weeds and garden debris around homes and buildings, and storing firewood and building supplies on racks or pallets above ground level are also practices that can limit or remove the animals’ sources of food, water or shelter.

Repellents

Using a repellent that changes the behavior of an animal may lead to a reduction or elimination of damage. Several available repellents, such as objectionable-tasting coatings or odor repellents, may deter wildlife from feeding on plants. Other repellents such as sticky, tacky substances placed on or near windows, trees or buildings may deter many birds and small mammals. Unfortunately, most wildlife soon discover that repellents are not actually harmful, and the animals may quickly become accustomed to the smell, taste or feel of these deterrents.

Chemical repellents applied outdoors will have to be reapplied due to rain or heavy dew, or applied often to new plant growth to be effective. Failure to carefully follow the directions included with repellents can drastically diminish the effectiveness of the product. Some repellents contain toxic chemicals, such as paradichlorobenzene, and are ineffective unless used at hazardous concentrations. Other more natural repellents contain chili pepper or capsaicin extracted from hot peppers.

However, even under the best of conditions, repellents frequently fail to live up to user expectations. The reason for this is twofold. First, many repellents simply don't work. For example, peer-reviewed publications have consistently shown that ultrasonic devices do not drive unwanted animals away.[citation needed] Second, even when the repellent has been shown to work, animals in dire need of food will "hold their nose" and eat anyway because the alternative is essentially death by starvation. Repellents are most successful (referring to products actually demonstrated by peer-reviewed research to be effective) when animals have access to alternative food sources in a different location.

Glue traps and boards

Glue traps and boards can be either a lethal or non-lethal method of control. Glue boards can be used to trap small mammals and snakes. Applying vegetable oil will dissolve the glue, allowing for release, but caution must be taken to avoid scratches and bites from the trapped animal.

Live trapping

Using traps can be very effective in reducing actual population numbers of certain species. However, many species cannot be trapped without a permit. In most cases, homeowners may trap an offending animal within 100 yards of their residence without a permit, however relocation is often illegal.

Traditional live traps such as cage or box traps are easily purchased at most garden centers or hardware stores. These traps allow for safe release of the trapped animal. The release of the animal to another area may be prohibited by state law, or may be regulated by the local Department of Fish and Game. Leghold traps may allow for either release or euthanasia of the trapped animal. Traps such as body-gripping traps, scissor and harpoon traps, as well as rat/mouse snap traps, are nearly always lethal. Knowledge of animal behavior, trapping techniques, and baits is essential for a successful trapping program.(Bornheimer, Shane P. "PreferredWildlifeservices.com" July 2013)

Frightening devices

Frightening devices such as bells, whistles, horns, clappers, sonic emitters, audio tapes and other sound devices may be quite successful in the short term for repelling an animal from an area. Other objects such as effigies, lights, reflectors and windmills rely on visual stimulation to scare a problem animal away. Often nuisance animals become accustomed to these tactics, and will return later if exposed to these devices daily.

Sonic nets

In 2013, Dr. John Swaddle and Dr. Mark Hinders at the College of William and Mary created a new method of deterring birds and other animals using benign sounds projected by conventional and directional (parametric) speakers.[1] The initial objectives of the technology were to displace problematic birds from airfields to reduce bird strike risks, minimize agricultural losses due to pest bird foraging, displace nuisance birds that cause extensive repair and chronic clean-up costs, and reduce bird mortality from flying into man-made structures. The sounds, referred to as a “Sonic Net,” do not have to be loud and are a combination of wave forms - collectively called "colored" noise - forming non-constructive and constructive interference with how birds and other animals such as deer talk to each other. Technically, the Sonic Nets technology is not a bird or wildlife scarer, but discourages birds and animals from going into or spending time in the target area. The impact to the animals is similar to talking in a crowded room, and since they cannot understand each other they go somewhere else. Early tests at an aviary and initial field trials at a landfill and airfield indicate that the technology is effective and that birds do not habituate to the sound. The provisional and full patents were filed in 2013 and 2014 respectively, and further research and commercialization of the technology are ongoing.[citation needed]

Laws

Before initiating any wildlife control activities, a person must become familiar with applicable federal, state, and local laws. One way to learn these rules is to contact the state's wildlife agency, which is usually responsible for selling hunting and fishing licenses. In general, property owners are permitted to prevent wildlife damage through exclusion and habitat modification, though they may be prohibited from disturbing an occupied nest or den, or directly harming an animal.

Many regulations exist in the United States concerning animal trapping including trap check intervals, usually requiring all traps be checked at least once during a 24-hour period. Some governments permit relocation of wildlife, however humane considerations must be taken into account before relocating wildlife, including population and habitat.

Ethics

There are many ethical considerations in nuisance wildlife management. Some species of wildlife cannot be ethically relocated due to overabundance of competing species, or lack of availability of proper food and habitat. Control during the spring months does run the risk of killing the young by starvation. Proper euthanasia of animals when necessary is also a controversial and sensitive consideration to be taken prior to engaging in nuisance wildlife management, and requires training and certification in some areas of the United States. [citation needed]

See also

References

  1. ^ Dieckman, E.; Skinner, E.; Mahjoub, G.; Swaddle, J.; Hinders, M. (June 2013). "Benign exclusion of birds using parametric arrays". The Journal of the Acoustical Society of America. 133 (5): 3536. doi:10.1121/1.4806387.
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