Wildlife Control
Wildlife sometimes accumulates to a level that it becomes a health concern, nuisance or causes serious economic losses. If this occurs, there are a variety of methods available to correct the problem. Nonchemical methods of managing wildlife populations are discussed in greater detail below.
It is important that the method of control chosen be cost effective and proportional to the problem. There are usually a variety of methods for controlling a pest and each of the available options should be carefully weighed before making a final decision. The ideal method of control is one that results in minimal injury to the problem species and maximum reduction of the problem whether it is unsightly animal droppings or reduction of crop yield.
The method of control chosen should be reasonably humane, safe, efficient and economical. Success of a control effort at minimizing a wildlife problem should be measured by the reduction in damage and not the number of animals killed.
Federal, state and local laws need to be followed. Special care might need to be taken to insure that control efforts do not harm an endangered species. It is wise to apply control efforts in a low-key, responsible manner without public display.
Wildlife damage control techniques available for use are listed below in their order of acceptance by the public:
- Tolerate losses
- Mechanical exclusion or protection
- Repellent devices and sounds
- Live trapping and transfer
- Habitat manipulation including flooding, clearing and burning
- Biological control methods
- Mechanical lethal control methods
- Chemical control
Tolerance of Losses
Everyone has a tolerance threshold when it comes to accepting damage caused by wildlife. It is always easy to tolerate wildlife damage happening to the property of another. Only when one is directly affected is a tolerance threshold tested.
Some people are willing to tolerate high levels of damage caused by wildlife, others very little. One’s background and personal beliefs all help in creating a person’s tolerance threshold. One end of the spectrum might be a person from India that believes that killing an animal is always wrong. At the other end of the spectrum might be an avid hunter with little qualms about killing an animal that is injuring his crop or spreading disease.
Some items to consider when deciding the level at which one is willing to tolerate an animal are listed below.
- Tolerating the animal allows it to possibly increase in numbers and cause additional injury or damage.
- Failure to control the animal may cause the problem to spread and become a hardship for others as well.
- The pest may have reached its carrying capacity at current levels and the population could be declining to a more suitable level without any action being taken.
- The pest population may surpass its carrying capacity, contract an epizootic and die back to tolerable levels.
- The pest may generate some beneficial results by causing a reduction in other pest species. Rattlesnakes are generally tolerated by Arizonans due to their suppression of desert rat populations.
- The pest may provide recreation, food, or income values outweighing its negative values. For example, many golfers enjoy seeing deer on a golf course, yet deer commonly eat flower plantings.
- The cost of controlling the pest could exceed the damage caused by the pest.
Mechanical Exclusion or Protection
Designing or modifying buildings, fences and machinery to exclude animals many times is the cheapest method of control in the long run. Some of the items to consider in deciding whether to employ this method of control are addressed below.
- Some crop and livestock areas are expansive, making exclusion by fencing prohibitively expensive and impractical.
- Fencing may pin in the damaging pest species and compound the problem.
- Fencing may affect nontarget species as well as the pest species.
- Fencing can restrict the escape routes available for livestock trying to escape predaceous animals and could actually increase losses.
- Fencing is expensive and many times the problem animal finds a way to enter the area that has been fenced off.
- Temporary netting for bird and bat control work well but may be too costly in time and labor. These are also not very aesthetic.
- Excluding pests from food can ultimately lead to lowering the carrying capacity of a pest and reduce its numbers.
Repellent Devices and Sounds
Repellants scare or ward off a pest without injuring the pest. Both sound and visual repellants are commonly utilized to ward off members of an animal species.
Sound. This includes the use of zon guns, firecrackers, firearms, music and distress calls to scare off animals. These sounds are either irritating to the animal or associated with danger.
Advantage –
- The pest is not killed and there is minimal impact on nontarget animals and the surrounding environment.
Disadvanatges –
- The pests may be driven to someone else’s property and cause a problem there.
- The pest becomes accustomed to the noise and is no longer scared away.
- This method may prove to be expensive and time consuming relative to the benefit achieved.
- The pest may begin to associate the noise with the presence of food. The noise may begin to attract the pest.
Visual repellents. Scarecrows, silhouette images and other visual repellents have been used for centuries to deter pests. Lights are sometimes effective at deterring nocturnal animals, especially when accompanied with noise. Items to consider when deciding on whether to use a visual repellant include:
- The effectiveness of a repellent depends on a number of factors including length of time over which the damage occurs, pest involved, past intensity of the pest and the visual repellent’s method of delivery.
- The effectiveness of a repellent can vary considerably.
- A repellant becomes less effective the longer that it is used.
- A variety of repellent devices used separately and then in concert are more effective than one method used continuously.
- The use of repellents can transfer problems from one place to another, delay damage which simply occurs at a later date or simply be tolerated or ignored by the pest which becomes conditioned to the repellent.
Live Trapping
This involves trapping the pest and relocating it to a sight far enough away that it will not return.
Advantages –
- There is no destruction of the animal.
- It is popular with the public.
Bears, mountain lions, eagles and other endangered species are handled in this way.
Disadvantages –
- It is often times difficult to find relocation sites.
- It is expensive in labor and materials.
- Return animal to the site of the problem is common.
- Survival percentage of relocated animals is often times very low.
- Diseases may be spread to new areas.
- The net effect of relocating an animal is often times a tremendous cost of time and money and death of the relocated animal.
Habitat Manipulation
Habitat manipulation is a method commonly used to manage an animal population. This involves destruction of the animal’s food source and shelter. Some examples of this include burning irrigation ditch banks, destruction of trees to remove nest and roosting areas of pest birds and mammals and flooding areas to kill rodents.
Advantages –
- This is a very effective method of reducing an animal population.
- It is acceptable to most protectionists since the animal is not directly killed.
Disadvantages –
- It ends up reducing the amount of wildlife in an area for recreational and aesthetic enjoyment.
- This is the method most damaging to wildlife and should be used as a last resort.
Biological Control
Biological control involves the use of disease agents, parasites or predators for the control of a problem pest. Its use for the control of wildlife pests has been a popular idea, yet to date, it has been of little help.
There is one success story, however. Myxomatosis virus disease was introduced into Australia to reduce their rabbit populations and it worked.
Mechanical Lethal Control
Mechanical lethal control involves the use of traps, snares, or dogs and may involve shooting the animal.
Advantages –
- There is no destruction of habitat.
- The problem is not moved to somewhere else.
- There are no other adverse effects besides killing the animal pest.
Disadvantage –
- This method of control has come under increased attack from preservation groups.
References
Bohmont, B. L. 2007. The standard pesticide users guide. 7th ed. Pearson Prentice-Hall, Upper Saddle River, N. J., Columbus, Ohio.