Module 1 Principles of Wildlife Damage Management
- Explain 3 reasons why wildlife damage management (WDM) is necessary.
- Describe the 3 major objectives of WDM.
- Explain the differences between biological and cultural carrying capacity, and how each relates to WDM.
- Explain the concept of carrying capacity.
- Explain why the concept of “balance of nature” is misleading.
- List the 4 major strategies of WDM.
- Provide some reasons why the removal of wildlife could fail to reduce the damage.
Terms to Know
Biological Carrying Capacity The maximum number of individuals of a given population that an environment can sustain.
Cultural carrying capacity (CCC) The number of animals that a human or human community will tolerate in a given area.
Diversion Luring animals away from protected sites, usually with a food attractant.
Exclude To prevent access, such as with the use of fences, netting, or securing holes.
Integrated pest management (IPM) An environmentally-responsible approach to pest management that involves the timely use of a variety of cost-effective methods to reduce damage to a tolerable level.
Relocation Moving an animal, but keeping it within its home range.
Repel To drive away.
Translocation Moving a nuisance animal from one place to another outside of its home range.
Based on the 2011 National Survey of Fishing, Hunting, and Wildlife-Associated Recreation (https://www.census.gov/prod/2012pubs/fhw11-nat.pdf), over 90 million US residents fished, hunted, or watched wildlife in 2011. They spent almost $145 billion pursuing these recreational activities, contributing to 35 million jobs in industries and businesses that support wildlife-related recreation. Conversely, economic losses associated with wildlife damage approach
$3 billion annually, demonstrating a clear need for effectively addressing negative impacts.
Wildlife damage management (WDM) is the process of dealing with vertebrate species that:
- cause damage to food, fiber, personal property, and natural resources;
- threaten human health and safety through disease, collisions, and attacks; and
- cause a nuisance.
A nuisance wildlife control operator (NWCO) is an individual trained to solve wildlife damage and nuisance wildlife situations, usually for profit.
Goals of WDM
- To reduce damage to a tolerable level,
- using methods that are cost-effective, and
- safe for humans and the environment.
Goal 1. Reduce Damage to Tolerable Level
Set reasonable goals. All NWCOs should avoid creating fear in clients, as this could lead to an overreaction to wildlife on their property. We must accept that there is a difference between a raccoon living in a house and a raccoon walking through a backyard (Figure 1). Be respectful and listen when clients explain their negative feelings about an animal. Do not reinforce inappropriate stereotypes or become drawn into a “problem” that does not need to be solved.
The focus of WDM is to reduce or eliminate damage, not reduce the number of animals in an area. Remind your clients that the goal is to solve a specific problem, not exterminate every animal in the area. Target only the animals causing a specific conflict.
Goal 2. Use Cost-effective Methods
If the expense of resolving a problem is more than the cost of the problem itself, it may not be practical to control the animal causing the damage. On the other hand, a $250 stainless-steel chimney cap may seem expensive, but when a client understands that the chimney cap will protect a chimney from raccoon invasions for decades, the cost may be reasonable. If the cap lasts 20 years, the annual cost of the cap is just $12.50. Thus, a chimney cap provides a long-term, inexpensive, and permanent solution, and provides clients with a tested method for excluding wildlife from the home.Goal 3. Use Safe Methods
People dealing with wildlife damage may be under stress, which could lead them to encourage the use of hazardous techniques. Just because a technique or method works does not mean it should be used. For example, mixing strychnine with cat food or putting out a bowl of radiator antifreeze may be effective in killing opossums and raccoons. These techniques, however, are irresponsible and illegal. Poisoning non-target animals can result in unnecessary suffering. Recommend the techniques you believe to be most appropriate, legal, effective, and safe for resolving the problem.
Integrated Pest Management (IPM) uses all appropriate pest control strategies to reduce pest populations to an acceptable level. Use an IPM framework in which you:
- identify the problem;
- consider a variety of solutions;
- implement the least harmful, most cost-effective strategies;
- monitor the problem to ensure that it has been solved; and
- evaluate the effectiveness of the solution you used.
If a client requests something beyond what you believe is legal, reasonable, ethical, or safe, you should suggest more reasonable alternatives or consider declining the job.
Key Concept – Overabundance
The concept of overabundance involves a population of wildlife in which its numbers may have exceeded both the biological and cultural carrying capacity.
Biological carrying capacity (BCC) is the number of animals in a population that an environment can sustain without long-term detrimental impacts. For example, when white-tailed deer become overabundant, a browse-line appears on shrubs, trees, and ornamentals. Plants will have few live branches below 6 feet, undergrowth will be dramatically limited, and plant diversity will be reduced due to over-browsing. Eventually, the deer population will decline due to starvation, disease, and competition. Long-term environmental damage will occur long before the deer population declines.
Cultural carrying capacity (CCC) refers to the number of animals in a population that people are willing to tolerate, based on the balance of environmental and social benefits and costs. For example, people in the Midwestern US typically are willing to tolerate about 30 deer per square mile. Their tolerance of deer-vehicle collisions and agricultural damage is influenced by the benefits they experience from viewing and hunting deer.
Problems with wildlife typically are greater when suitable habitat (food, water, and shelter) are available. Effective WDM requires understanding that change occurs in wildlife populations when habitat changes. When a client asks, “Why did the animals choose my house and property?” the simple answer is because their home and landscape supplied necessary resources (e.g., food, cover, water, and resting areas). Environmental or behavioral factors eventually will limit animal abundance (Figure 2). However, public tolerance may be exceeded long before animal numbers reach levels where environmental or behavioral factors limit population growth.
Wildlife populations are not static. Wildlife populations may fluctuate dramatically, both within and among years. Reasons for the fluctuations vary. Rodent and other prey populations frequently increase in numbers in response to suitable environmental conditions such as sufficient rainfall and mild winters. As the number of prey animals increases, the number of predators also may increase, although usually in the following year. Local wildlife populations can change due to human activity such as residential development, the addition or removal of bird feeders or gardens, and improper trash storage (Figure 3).
Will Predators Solve the Problem?
A common misconception is that wildlife is “out of balance” with nature because humans have removed predators from the system. While it is true that populations of many top-level predators have been reduced dramatically, it is unlikely that restoring their numbers to pre-colonial levels would solve most human-wildlife conflicts. Often human tolerance of damage by wildlife is quite low. Homeowners do not want to have fewer squirrels in their attic; they want NO squirrels in their attic. Predators typically do not control populations of prey. If a predator substantially reduces prey populations, the predator would threaten its own existence by eliminating its source of food. For example, bats foraging in a yard will never make the area free of insects.
Even a cat that is skilled at catching mice often cannot control a rodent infestation in a house (Figure 4). In addition, many predators are not selective in their choice of prey, so non-target animals may be taken.
Strategies to Reduce Wildlife Damage
All methods for WDM fall into 4 strategies.
- Clean up. Reduce the carrying capacity of the area, which reduces the number of animals the habitat can sustain over time.
- Exclude or prevent animals from accessing a location.
- Repel or divert animals from the area.
- Reduce the number of animals by lethal and non-lethal control methods.
Strategy 1. Clean Up Sites to Reduce Carrying Capacity
Remove food, water, or shelter to reduce the biological carrying capacity and thus, the number of animals in an area. For example, if someone is having conflicts with mice, implementing rigorous clean up and removal of available food likely will reduce mouse numbers (Figure 5). You could aggressively trap to reduce the population, but mice likely will reproduce faster than your trapping efforts can control them, particularly when plenty of food and shelter are available.
Strategy 2. Exclude Animals
Prevent access of animals to potential damage sites to provide long-term protection from damage. Exclusion techniques include closing entry holes in buildings, installing bird nets over fruit trees, and constructing deer-proof fences around orchards. Development of exclusion techniques and devices is an active area of entrepreneurship, with new and interesting products frequently appearing in the market.
Strategy 3. Repel or Divert Animals
Another WDM strategy is to repel or divert animals from a location. Repellents are based on pain, fear, touch, or conditioned aversion. Several repellents and frightening devices are available, depending on the problem. Many of these products, however, have not been tested adequately under research conditions and may fail to prevent damage.
Diversion is the process of luring animals away from protected sites, usually with a food attractant. Although this may sound good in theory, few practical applications exist. First, you need to find a food source that is more attractive than what the animal is currently using. Also, by increasing the availability of food, population levels may increase, adding to the potential for damage on the property. The effectiveness of diversion often is questionable. The impact of both repellents and diversion almost always is short-term.
Strategy 4. Reduce the Number of Animals
The number of animals can be lowered using toxicants, trapping, or shooting. Such actions typically lead to a rapid decrease in the population to a level in which they, or their associated damage, can be tolerated. Lethal control alone, however, often fails to reduce long-term damage. As long as suitable habitat and food resources are available, populations may rebound quickly (Figure 6). Well-fed animals often have larger litters and greater success in raising young to maturity. Population reduction sometimes fails because animals often move into an area that has been vacated.
For example, you may have successfully removed voles from a particular property at a given time. However, your client did not understand that other voles would quickly move in from neighboring properties where you did not have permission to work, and soon occupy the habitat previously used by the voles you removed.
Relocation and Translocation
Relocation refers to moving and releasing an animal off the property where it was captured but within its home range. This is sometimes referred to onsite release. This is usually a short distance away from where it was captured.
Translocation refers to moving and releasing an animal a greater distance from where it was captured. Translocated animals are no longer within their home range. People generally think translocation means the same as relocation.
Moving animals through relocation or translocation is not recommended. If an animal must be moved, it should be moved as short a distance as possible. For the best chance of survival, the animal should be released within its home range.
Moving an animal may spread disease or create damage problems in new places. Translocated animals rarely stay in the area of release and often have low survival rates because they cannot find suitable habitat. As a result, these animals often experience a slow and stressful death, as opposed to a quick and humane death administered by a trained NWCO. New York State law prohibits relocating or translocating wildlife, except when animals are removed from inside dwellings or structures and released in the immediate vicinity outside these buildings on the same property. However, licensed NWCOs are allowed to relocate most species of wildlife with written permission of the landowner where the wildlife will be released. NWCOs also must contact the county health department before relocating any rabies vector species (bats, raccoons, or skunks).
Many people believe that wildlife cause damage to property because “humans have taken away their homes” or that urbanization has destroyed their natural habitats. When resources are available, wildlife is abundant and they are very comfortable in urban environments. Urban sprawl has reduced habitat for some animals such as forest birds and large predators, but it has created and supplied habitat for other more adaptable species such as gulls, raccoons, and deer.
Some animals thrive in human-impacted environments because:
- urbanization creates novel habitats;
- urbanization provides food for animals through bird feeders, trash cans, pet dishes, gardens, and compost piles;
- protective regulations enable some wildlife populations to become overabundant; and
- lethal control of wildlife is illegal in some areas due to local regulations and concerns with safety.
Populations of white-tailed deer (Figure 7) have increased dramatically across much of the US for several reasons:
- expansion of their preferred habitat (wooded edges, fields, and open spaces),
- reduced hunting pressure (fewer people hunt and more land is closed to hunting),
- lower numbers of natural predators in suburban areas, and
- a long-term trend toward milder winters.
Study Questions for Principles of Wildlife Damage Management
Questions for Reflection
- Explain why the statement “balance of nature” may be misleading.
- A client does not want to modify a bird feeder to reduce rodent access to bird seed. What would you tell the client about the benefits of doing so?
- After recommending trench-screening to protect a deck from skunks, your client expresses resistance over the price. How would you help the client appreciate the value of the exclusion?
- You have had difficulty in removing muskrats from a pond. The client, angry over the damage to the water levee, suggests dumping motor oil in the water to eliminate the muskrats. How would you respond?
- A goal of WDM is to
- change the habitat
- remove animals
- reduce damage to a tolerable level
- do whatever the client pays for
- none of the above
- Select the correct term – Cultural or Biological
- __________carrying capacity relates to when wildlife conflicts have reached a level people will not tolerate
- __________ carrying capacity relates to when habitat is harmed by the wildlife
- Habitat modification
- reduces the total number of wildlife that can be present.
- reduces wildlife numbers over the long term.
- is considered a non-lethal form of management.
- all of the above.
- All of the following can be reasons why a wildlife control program might fail EXCEPT
- animals moved into the area.
- you reduced the amount of food and shelter available.
- the devices you used did not frighten the animals.
- you did not catch the target animals.
- True or false – Residential development will only reduce the number of animals in an area because it removes habitat for wildlife.
- a cultural b. biological