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Running head: METHODS FOR CONTROLLING FERAL HOG POPULATIONS 1

Practical and Economical Methods for

Controlling Feral Hog Populations

Dustin Freeman

Texas Tech University

METHODS FOR CONTROLLING FERAL HOG POPULATIONS 2

Abstract

Feral hogs (Sus scrofa), since their introduction to the United States by European

explorers around the mid-1500’s, have negatively impacted the environment and have generated

billions of dollars in damage over the years. In the United States, along with many other places

around the world, the need for the removal of this species is essential to the protection of natural

habitats, wildlife, crops and livestock. This paper intends to look at the economical impact the

feral hog has on the environment, and the subsequent economic benefit and cost efficiency of

different removal methods needed to reduce the feral swine population.


Practical and Economical Methods for

Controlling Feral Hog Populations

Introduction

Since European colonization in the early 1500’s, more than 30 species of alien-invasive

(non-native) free-ranging mammals have become established in the United States (Seward,

VerCauteren, Witmer, & Engeman, 2004, p. 34). Since their introduction by early Spanish

explorers some 500 years ago, feral hogs (Sus scofra) have rapidly spread and colonized into

many different areas of the United States. Feral hogs (also known as feral swine), “are the most

abundant free-ranging, exotic ungulate in the United States and have become widespread

because of their reproductive potential and adaptability to a wide range of habitats” (Seward

et.al., 2004, p. 34). Although feral hogs can survive in dry climates, they are mostly found in

areas that provide dense cover and water rich surroundings that provide adequate protection.

Their ability to adapt to almost any environment along with few natural enemies and high

reproductive rates contribute to their overpopulation.

With an estimated 4 million feral hogs in the United States alone, they cause

approximately 800 million dollars in damage each year (Pimentel, Zuniga, & Morrison, 2005, p.

280) that includes damage to crops and natural habitats, the decimation of endangered species,

depredation of wildlife and livestock, and increasing costs associated with the spreading of

disease. Feral hogs are typically the most destructive modifier of plant communities that is

caused by their rooting which damages plant structures and can also change species

compositions (Engeman, et al., 2004, p. 144). There is no doubt that the number of invasive

feral hogs have increased from 2005 to present as well an increase of their economical impact on

the environment and surrounding wildlife. By understanding this issue from both a Wildlife


Management perspective and an Economical perspective, we can better understand through each

discipline’s insights which methods are best suited for controlling the increasing feral hog

population. Utilizing an interdisciplinary process presents the best way to understand each

disciplines insights, create common ground between these disciplines, and integrate disciplines

insights so we can apply them to future research.

Step 1: State the Focus Question

The overarching question of which methods are the most practical and economical to

control the increasing feral hog population have been tested and researched for many years.

Some have been successful, and others have not. Some methods are extremely simplistic in

nature, while others require extensive scientific design and production. Through research of the

damage that feral hogs cause to the environment, forest and natural resource managers have

begun to understand the need to find both practical and economical methods to reduce not only

the feral hog populations, but also the monetary damage that this species creates.

“Unfortunately, many of these feral swine damage management programs are not adequately

funded and lack clearly stated or realistic objectives” (Campbell & Long, 2009, p. 2319).

In terms of practicality, which methods can be easily replicated and do not require

substantial consumer education. Which of these methods can be easily transported from one area

to the next? The most practical methods are methods that farmers, ranchers, wildlife extension

agents, and researchers can implement to facilitate the adaptive management of feral hog

populations.

Economically, we must first determine the amount of environmental damage that is

caused by the feral hogs. A study of the different methods to determine their economical impact


will help determine which control methods are the most cost-effective. Without base line

knowledge of the impact caused by this alien-invasive species, there can be no cost-effective

analysis conducted on different control methods.

Step 2: Justify an Interdisciplinary Approach

The issue of trying to cut down on the ever increasing feral hog populations is not a

problem that can be defined nor solved by one specific discipline. To understand and find

effective solutions, we must utilize two different disciplines to synthesize and integrate their

ideas and methods.

Utilizing the Wildlife Management discipline will help us understand the major questions

related to the issue at hand. We must understand how the feral hogs interact with the

environment, what type of damage they typically cause, and how they interact with other wildlife

to fully understand what type of animal we are dealing with. The Wildlife Management

discipline is best suited for this task. The in-depth knowledge about these ungulates will help

give a better perspective on the most practical methods for controlling their populations.

Without utilizing economics as a discipline, we would never truly understand the

economical impact that these animals have on the environment, nor would we be able to

understand the cost effectiveness of the different methods used. Both of these disciplines are

integral in fully comprehending the complexity of the problem and will give insights to each

disciplines perspectives that allows us to integrate both insights to form a more holistic solution.

Step 3: Identify Relevant Disciplines

The first relevant discipline that was identified to solve this problem was the Wildlife

Management discipline. This discipline is relevant to the problem because a Wildlife manager is

in charge of taking the appropriate steps needed to keep animal populations well-maintained. As


mentioned above, the major issue relevant to this paper is the increasing feral hog populations.

Wildlife managers also control nuisance animals such as the feral hog. They have a duty to

protect the environment from non-native species as well as educate the general public and

respond to requests for assistance. This discipline is also vital in testing and developing new

methods to help control the feral hog populations. This would include methods that would be the

most practical in decreasing the feral hog populations while minimizing the potential hazards to

other non-target wildlife.

The second discipline that is most relevant to the problem is the economics discipline.

Economics is important because there is a need to determine the feral hog’s economic impact to

the environment. This means that there is a need to look at the environmental impact associated

with each feral hog as well as determine the cost effectiveness of the methods that are produced

from the Wildlife Management discipline. A study of the economics of both the damage created

by the feral hog and the cost effectiveness of the methods suggested are important to solve the

feral hog issue.

Step 4: Conduct a Literature Search

Through an in-depth literature search, there were many scholarly articles that I

discovered that offer some great insights into some practical and economical methods for

controlling the feral hog populations. In the article “Adaptive and Economic Management

Methods for Feral Hog Control in Florida”, it details how an effective cost analysis can be

constructed to determine the economic impact of feral hog populations. The population of the

feral hogs in the area first had to be established to calculate the damage impact. The use of a

passive tracking index, or PTI, as a low-tech method of assessing the population index of the

feral hogs proved worthwhile. By applying Quadrat sampling and line intercept sampling, the


researchers were able to (1) estimate the number of feral hogs in the area, and (2) it gave them

the ability to quantify that data to show the economic damage of the feral hog to multiple areas

by measuring the distance between sampling areas. This data can be further used in different

areas across the country to estimate feral hog populations and their economic impact to the

surrounding natural habitats.

Another important article discovered through the literature search was the article “Too

many hogs? A review of methods to mitigate impact by wild boar and feral hogs”. This article

mentioned that some groups have voiced opposition to the traditional methods for controlling

feral hogs such as poisoning, shooting, etc. This paper discusses both lethal and non-lethal

methods for controlling feral hog populations. There is a lot of discussion about the feasibility of

non-lethal methods such as trapping which take considerable amounts of effort, time, and money

to conduct. The feasibility and cost of each method is discussed to assess which method would

be the best in different scenarios. The costs are different in each area due to state laws,

regulations, resources and a variety of other different variables. The most successful operations

utilized an integrated approach where several different methods were used simultaneously.

Step 5: Developing Adequacy

Two of the main theories that are used in the Wildlife Management discipline have been

the disturbance theory and the foraging theory. Disturbance theory is a temporary change in

environmental conditions that can cause an effect or change in an ecosystem. While some minor

disturbances are flooding, windstorms, and earthquakes, major disturbances can include clear

cutting, forest clearing and invasive species. The foraging theory, or optimal foraging theory, is

the study of foraging behavior and states that organisms forage in such a way as to maximize

their net energy intake per unit time. These theories are important because they are vital to


understand how to best eliminate the invasive feral hog populations.

The Wildlife Management discipline focuses on quantitative research. In the research

that I have conducted so far, the vast majority of the information that is gathered during the

research process is numerical data. This data usually contains information relating to the

efficiency of methods that are used to control the feral hog populations. Quantitative research is

more beneficial and educational that qualitative data would be.

In economics, the use of the benefit-cost analysis is typically applied to different

scenarios where a value is needed to be place on control methods for reducing populations of

species that are highly destructive. This analysis can also be used to determine the economical

impact that the feral hog has to the environment. Economics also gives us the ability to

determine which practical methods would be the most economical in terms of effectiveness of

reducing populations.

Step 6: Analyze and Evaluate

The Wildlife Management discipline seems to be the forefront leaders in attacking and

trying to resolve this problem. Their researchers are the ones conducting the different

experiments to see which methods work the best. The disciplinary perspective from the Wildlife

Management discipline would be that there is a clear acknowledgement of the increasing

population issue and there the real need to decrease their populations before they become

uncontrollable. They understand that this needs to be done in a method that is humane while

taking into consideration the amount of damage this species can do to farms, ranches, and the

environment.

There is currently no panacea for feral swine control, management, or eradication

(Seward et al., , 2004, p. 37). In many states, including Texas, feral swine are non-native and


therefore considered pests. The hunting of feral hogs is typically unregulated and they can be

harvested throughout the year. You cannot simply just spray a chemical to kill the feral hog

without a high risk of endangering other wildlife in the area. So there has to be a lot of

preparation and study that goes into the methods that best reduce the feral hog populations.

There are many different methods that have been introduced to try to reduce populations. These

methods include: trapping (low-efficiency & labor intensive), shooting (low-efficiency), aerial

shooting (high-efficiency & more restrictive to environmental conditions), fencing (ineffective &

expensive), and toxicant bait systems (Lapidge, Wishart, Staples, Fagerstone, & Campbell, 2012,

p. 20). Toxicant baiting of feral swine is currently not allowed in the U.S., but there are a few

field testing sites that need to be studied in Texas and Florida in order to obtain government

approval.

Shooting and trapping feral hogs is a great way for the ranchers, farmers, or land-owners

to generate income to offset the damage that the feral hogs create. This allows them to let

hunters onto their land for a fee to track, hunt, and shoot the invasive species. However, these

two methods are not very effective at reducing the overall populations (Seward et al., 2004, p.

37). Some research has been conducted that looks into the use of pharmaceuticals to try to

reduce the population. One study in Australia concluded that delivering pharmaceuticals orally

has been highly successful. This methods yielded >90% removal of feral swine (Campbell et at.,

2006, p. 1187). Ongoing studies are being conducted to test the feasibility of adding fertility

control agents to the baits as well.

The economic discipline is focused on reducing the feral hog populations by asking how

much damage the feral hogs create each year as well as offer the quantitative data to determine

which methods are the most economically viable. The disciplinary perspective from an


Economic stand point is which method that is currently being used or tested is the most

economical. Does this method cost more to reduce the hog population than the damage they

create? By utilizing a passive tracking index, it has been found to be the most efficient means of

estimating the number of feral hogs in a given area. This index can then be used to make

estimations for larger tracts of land. The passive tracking index is a low-tech and low-cost

method of placing tracking plots throughout an area of interest to determine the number of feral

hog intrusions in each plot.

By estimating the damage value associated with feral hog destruction allows an effective

benefit-cost analysis to be conducted to evaluate the necessity of hog control from an economic

perspective. The benefit-cost analysis also allows us to estimate the monetary value and

economics of hog management approaches (Engeman, et al., 2007, p. 181).

Step 7: Identify Conflicts

The major conflict that occurs within the scholarly literature that I have found seems to

lean towards the difference in the discipline’s approaches. From an economic perspective, they

tend to learn towards just interpreting the quantitative data from a numerical perspective. They

look at the different methods and can interpret which methods work the best by simply analyzing

the data. Whichever method costs the least to run versus its effectiveness would numerically

seem to be the best method. However, the Wildlife Management discipline approaches the

problem in a different way. While they look at the cost of the methods as well, they take into

consideration that effect that method has on the feral hog itself as well as the surround

environment and wildlife. Since their approaches are a different, it is very important to be able

to integrate both approaches to find the best method for controlling the feral hog populations.


There is no vocabulary issue between the two disciplines because the economic

disciplines do not take into account what effects the methods have on other wildlife and the

environment. It is strictly a numerical approach. The same goes for the different phenomena.

Wildlife Management has their own theories as to how and why the populations got as large as

they are today.

Step 8: Common Ground

Both the Wildlife Management discipline and the Economic discipline have a lot that

they can offer each other in terms of common ground. While their perspectives might differ, the

approaches that they use to consider which methods are the best are similar. Wildlife managers

and economist both use quantitative data to determine the efficiency of the methods used to

reduce hog populations. Wildlife managers and researchers use economic principals when

conducting their research to determine the feral hog’s economic impact to the environment.

In an article researching feral hog economic damage to a basin marsh in Florida, they

used economic valuations to appraise the monetary land value based on current market

conditions. The only problem with this scenario is that special habitats, such as the wetlands of

Florida, have little or limited “market value” (Engeman, et al., 2007, p. 145) which makes it hard

to specifically determine a damage impact ratio. However, this method has been extremely

successful in determine the damage impact ratio on land that is privately owned because a fair

market value of the land is more easily determined. The cost-efficiency ratio of the methods

used in the study was determined to be too large for the economic impact from the hogs.

Step 9: Integrate

The integration of both disciplines in important to help fully comprehend and realize a

holistic solution to decreasing feral hog populations. When we think about which method or


methods are the most practical in a manner that can be easily replicated, we think about hunting,

shooting or trapping. These methods are generally the least expensive to replicate because they

materials involved are generally the cheapest to obtain, yet they have very low efficiency ratios.

When we think about the method that would be the most efficient in reaching the largest

number of feral hogs, oral delivery is considered to be the most viable option. As most feral

hogs eat a variety of food including small mammals, fruits, nuts, and corn that is typically found

around deer feeders, the oral delivery can be easily produced into bait that can then be placed in

areas of high traffic to increase the likelihood of ingestion. The use of these baits, laced with a

specific amount of sodium nitrate, is ingested by the target animal using a proprietary invention

called the Hog-Hopper™ (Lapidge, Wishart, Staples, Fagerstone, & Campbell, 2012, p. 19). The

Hog-Hopper™ generally only allows the feral hog, which uses it’s very strong snout, to lift open

the feeder lid to gain access to the baits. Sodium nitrate causes a reaction in the feral hogs

system that causes a quick depletion of oxygen to the brain and vital organs which ultimately

causes a shutdown of the animal’s body. Feral swine lack methemoglobin reductase which is a

naturally occurring enzyme that is needed to reduce the sodium nitrate poisoning (Lapidge et al.,

2012, p. 20).

Integrating the economics perspectives and apply them to the different methods that have

been used and studied so far show that there is definitely a need for intervention. The feral hog

damage impact to the environment, estimated to be around $800 million per year, shows just

how destructive these species are to the environment. Using cost-efficiency analysis of the

methods used will help demonstrate the methods that are the most cost-effective and will benefit

the cause the most. Without integration of these two disciplines, there would be no possible way

to determine the impact that they have to the environment nor the cost-efficiency of the different


methods studied.

Step 10: Communicating

Using both economics and wildlife management theories and practices prove that each of

these methods have pros and cons. None of these methods developed and tested to date can

systematically show that they have a large impact in reducing feral hog populations. However,

both disciplines are integral in providing data to each other in order to determine which methods

are best suited to help the problem.

I believe that even though some of these methods such as trapping, shooting, and aerial

shooting are not considered to be highly efficient, I think that they are only helping to reduce the

feral hog population. The use of these methods will help stimulate the economy in terms of

ammunition purchased, meat sold to food packers, meat donated to help out families in need, and

money to help offset land-owner expenses.

The method of oral delivery of pharmaceuticals is the most efficient in reaching the

largest number of feral hogs. However, its economical impact has yet to be determined due to

continued research and testing of the Hog-Hopper™ and Hog-Gone bait systems. It is hoped

that the EPA will approved the further distribution and manufacturing of these products in late

2015 (Lapidge et al., 2012, p. 23). The impact that orally delivered baits has had on populations

in Australia show to be extremely promising. With the further testing of these products

throughout the U.S. will increase the studies effectiveness and overall success.

It is my belief and opinion that while these methods have been somewhat successful in

reducing some of the population, the continued development of new methods to more effectively

and efficiently reduce the feral hog population needs continued support from land-owners and


specifically the U.S. Federal government. All methods should be employed to reduce their

populations to give us the best chance at keeping the feral hogs from continuing to rise.


References

Campbell, T. A., & Long, D. B. (2009). Feral swine damage and damage management in forested ecosystems. Forest Ecology and Management, 2319-2326.

Campbell, T. A., Lapidge, S. J., & Long, D. B. (2006). Using Baits to Delive Pharmaceuticals to Feral Swine in Southern Texas. Wildlife Society Bulletin, 34(4), 1184-1189.

Engeman, R. M., Constantin, B. U., Shwiff, S. A., Smith, H. T., Woolard, J., Allen, J., & Dunlap, J. (2007, 1 1). Adaptive and Economic Management Methods for Feral Hog Control in Florida. Human-Wildlife Conflicts, 1, 178-185.

Engeman, R. M., Smith, H. T., Severson, R., Severson, M. A., Shwiff, S. A., Constantin, B., & Griffin, D. (2004). The amount and economic cost of feral swine damage to the last remnant of a basin marsh system in Florida. Journal for Nature Conservation, 143-147.

Lapidge, S., Wishart, J., Staples, L., Fagerstone, K., & Campbell, T. (2012). Development of a Feral Swine Toxic Bait (Hog-Gone) and Bait Hopper (Hog-Hopper) in Australia and the USA. In S. N. Frey (Ed.), 14th Wildlife Damage Management Conference, (pp. 19-24). Nebraska City.

Pimentel, D., Zuniga, R., & Morrison, D. (2005, 2 15). Update on the environmental and economic costs associated with alien-invasive species in the United States. Ecological Economics, 52(3), 273-288.

Seward, N. W., VerCauteren, K. C., Witmer, G. W., & Engeman, R. M. (2004, 10 16). Feral Swine Impacts on Agriculture and the Environment. Sheep and Goat Research Journal, 19, 34-40.

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