Project Accomplishments

Project Accomplishments


Feral Swine Damage Control Strategies

PROJECT GOAL: Generate and disseminate applied ecological information related to developing tools to control feral swine damage and wildlife diseases that affect humans and livestock.

Project Accomplishments 2010

Feral Swine
Free-ranging populations of wild pigs (also called feral swine) exist in at least 39 U.S. states. Some experts estimate the number of wild pigs in the United States at over 4 million, with the largest populations located in California, Florida, Hawaii, and Texas. Wild pigs feast on field crops, are efficient predators of young livestock and other small animals, and transmit diseases to domestic livestock. Developing effective methods and tools for managing wild pig populations is essential to protect agriculture and livestock from the threats these animals pose.

Evaluation of Boar-Operated-System (BOS™) Feeder: Nontarget Hazards—Feral swine (Sus scrofa) pose a significant disease threat to livestock and humans. Emerging technologies to reduce risks associated with the transmission of diseases by feral swine include fertility control, vaccination, and toxicants. However, for these technologies to be appropriate for field application, a feral swine-specific oral delivery system is needed.

In a recent study, National Wildlife Research Center (NWRC) researchers tested the effectiveness of the BOS, an oral delivery system designed to provide bait access only to feral swine. The researchers evaluated and monitored 10 BOS units for wildlife visitation, bait removal, and ingestion using motion-activated photography and baits containing the bait marker tetracycline hydrochloride (TH). Three of five pre-baited BOS units were used exclusively by feral swine. Additionally, five BOS units that were not pre-baited were not used by either feral swine or non-target wildlife. BOS units reduced bait removal by 10% for feral swine and by 100% for all other wildlife. Of the 81 feral swine and 23 raccoons captured in the study area, 90% and 13%, respectively, had TH-marked teeth.

These results show that, with minor modifications, the BOS could be a valuable tool for use in managing feral swine diseases.

photo of fencing to exclude feral pigsEvaluating Feral Swine Fencing for Use During Disease Outbreaks— Feral swine ( Sus scrofa) are susceptible to many diseases that are transmissible to cattle (e.g., foot-and-mouth disease, bovine tuberculosis, brucellosis) and domestic swine (e.g., classical swine fever, African swine fever). Animal health officials and wildlife managers need ways to effectively and quickly contain feral swine during disease outbreaks.

In collaborations with researchers at the University of Nebraska, NWRC scientists evaluated five candidate fences and, based on efficacy, selected traditional 0.86-meter-high hog panels to test rigorously for containing feral swine with increasing levels of motivation. During 4-day trials, the fences proved 97% successful when feral swine were least motivated (relatively undisturbed by humans), 83 percent effective when motivated by humans with paintball projectors, and 100% successful when pursued by gunners in a helicopter. The researchers also conducted two longer, 14-day trials where only one of six feral swine escaped.

In addition to being effective in containing motivated feral swine, enclosures constructed of hog panels were easy to erect and inexpensive ($5.73 per meter, excluding labor) relative to other fencing options. Hog-panel fence structures therefore offer a valuable tool for managing feral hog populations.

Activity Patterns of Feral Swine—Free-ranging feral swine ( Sus scrofa) are increasing in abundance and geographic distribution throughout North America. Currently, there are established populations of feral swine in Arizona, California, Colorado, Kansas, Nevada, New Mexico, Oklahoma, and Texas. Information on their natural history, such as daily and seasonal activity patterns, is not available for much of the Southwest, and there is evidence that these patterns may vary by region.

In 2008, NWRC researchers studied feral swine activity patterns and the impact of temperature on those patterns in southern Texas. The researchers placed GPS collars on 25 feral swine. Feral swine displayed highly nocturnal activity patterns, and during the dormant and early growing season (January through March), activity increased with rising temperatures. However, data for summer (May through July) suggest no influence of temperature. These data are counter to observed reductions in the success of feral swine trapping during summer months. The researchers believe that reductions in summer trapping success may be due to the availability of alternative forage associated with the growing season and, therefore, are not directly related to temperature.

These findings provide useful information for wildlife managers, as they can better focus their work depending on the season and environment. For example, during summer droughts, trapping success may increase by targeting trapping efforts near sources of water.

Feral Swine Toxicant—Feral swine populations are growing throughout the United States. This population growth also means an increase in their threats of spreading diseases and damaging property. To help control feral swine populations safely, wildlife managers need effective means of delivering toxicants to these animals without impacting non-target groups. NWRC scientists, in collaboration with a private company, conducted trials to develop a palatable placebo bait for feral swine.

In this study, the scientists offered two baits (developed at Genesis Laboratories, Inc.) to 10 feral swine for three days. One bait contained strawberry flavoring, and the other had no added flavoring. On average, the feral swine consumed 1.937 kilograms more of the bait without flavoring compared to that with flavoring. To determine the best toxicant to use in the chosen bait, scientists tested two active ingredients: warfarin (0.005%, 0.0125%, and 0.025%) and diphacinone (0.001%). Results showed that warfarin was more effective. The scientists then conducted field tests to determine potential non-target hazards when using a swine-specific, bait delivery system. They placed placebo baits into specially designed feeders. Various animals, including collared peccary ( Dicotyles tajacu), Norway rat ( Rattus norvegicus), raccoon ( Procyon lotor), and coati ( Nasua nasua), visited the feeders and sampled baits when the lid was open, but once the lid was closed, only collared peccary gained access to the bait.

These findings show that, to reduce non-target exposure to toxicants, wildlife managers should limit baiting to areas where collared peccary are not present. The researchers also recommend close collaboration and planning with State authorities to ensure human and wildlife safety if toxicants are to be used with feral swine.

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