A Strategic Approach to Wild Pig Management

By: Josh Helcel, Extension Associate

The adaptability, intelligence and high reproductive capacity of wild pigs often requires that land managers employ all of the tools in their toolbox to reduce wild pig (Sus scrofa) populations.  In Texas, lethal control methods include trapping, aerial gunning, snaring, shooting, and the use of trained dogs. Non-lethal measures such as contraception and vaccination remain largely impractical (West et al. 2009), however non-lethal practices such as exclusion and electrified fencing can help to reduce agricultural damage, supplemental feed consumption, and increase the effectiveness of lethal control efforts (Muir and McEwen 2007; Reidy et al. 2008; Timmons et al. 2011 ).  Research conducted on successful abatement efforts found that the order in which wild pig management tools are implemented can significantly impact success (Parkes et al. 2010; Schuyler et al. 2002). This article will discuss how these efforts were carried out, and will also detail some considerations to make when deciding when and how to enact control measures for wild pigs.

Santa Cruz Island Study
This study documented the removal of 5036 wild pigs from the 25,000 ha (61,776 acres) island in 411 days (Parkes et al. 2010). One of the significant factors about this effort was the deliberate and non-overlapping order in which control measures were enacted. Researchers began by using exclusion fencing to divide the island into 5 zones. Trapping activities were then conducted with no other active control strategies used during the trapping period. This was an intentional consideration given that aerial gunning, shooting, the use of dogs or any other control measure can potentially reduce trapping success. Aerial gunning activities followed trapping, and shooting preceded the final measures of trained dogs and sterilized adult wild pigs fitted with radio collars to aid in targeting remaining animals.

The speed and success of removal was noted as being at least twice as fast as any previous effort, and the study credited the “deliberate sequencing” of control methods as an integral component for success. The rationale for the strategic sequencing was to first use tools that pressured or “educated” surviving pigs the least with the use of trained dogs being the final control measure (Figure 1). 

         

Figure 1. Research indicated that trained dogs can serve as an effective final control measure after other abatement efforts have significantly reduced populations (Schuyler et al. 2002; Parkes et al. 2010, Photo Credit: Opie Dauphin).

Santa Catalina Island Study

This effort used sequenced control measures similar to those used in the Santa Cruz island study to remove 11, 855 wild pigs over a period of 11 years from the island of Santa Catalina (Schuyler et al. 2002). This study cited the use of a variety of control methods as a key component for success, but further observed that time of year impacted the success of varying methods. For example, trapping was found to be most effective both as an initial measure and especially during times when resource availability was low. The use of trained dogs was again found to be most effective as a final control measure but was especially preferable to other methods when resource availability was higher.

This research also noted that aerial gunning activities were less effective as vegetation density increased. Success increased in more open areas and during times of the year with reduced canopy cover (Figure 2). As the study progressed, researchers documented that overall trapping effectiveness declined as wild pig numbers decreased. This was used as an indicator to enact other control strategies.  

Figure 2. Aerial gunning success can be increased in areas with greater visibility and by concentrating efforts during times of the year with reduced canopy cover.

Tying It All Together
Texas is hardly an island. Exclusion fencing is considered to be the most expensive of all control methods and in some circumstances may not be a financially feasible option. However, there are some things that can be learned from these successful wild pig eradication studies. Timing can be a huge factor in the success of wild pig abatement efforts. Below are a few observations based in both research and personal experience that may help with the application and timing of wild pig management tools.

1.      Begin with trapping, especially when exclusion fencing is not a viable option. Corral trapping is generally more successful than box trapping; however both methods can be successful depending on the situation. Consider conducting trapping efforts during periods of low resource availability to increase your chances for success. Mid to late winter and mid to late summer are good times to start. While trapping, consider refraining from other control methods or at least direct them elsewhere (Parkes et al. 2010).

2.      Aerial gunning is an effective tool to reduce populations and is a great secondary tool to follow trapping efforts. Success with this method can be dependent upon visibility (Schuyler et al. 2002), and consider timing these efforts to times when canopy cover is reduced.

3.      Snaring has been shown to be effective both alone and in conjunction with exclusion fencing to prevent intrusion attempts (Muir and McEwen 2007). Consider a monitoring protocol for any exclusion fencing and time snaring efforts to deter intrusion attempts by wild pigs.

4.      Shooting, hunting and the use of trained dogs are methods that will not reduce wild pig populations. They are, however, excellent tools to pressure animals out of areas where they are causing damage. Successful abatement efforts generally utilize these tools as final measures to remove residual wild pigs after all other control measures have been enacted and populations have already been significantly reduced (Caley and Ottley 1995; Schuyler et al. 2001; Parkes et al. 2010; Muir and McEwen 2007).

5.      Wild pigs have been shown to eventually breech most types of fencing (Reidy et al. 2010). However, fencing can potentially increase the success of other control strategies and can be especially viable as an alternative for small tract landowners and those in urban areas.

Conclusion

Until toxicants such as sodium nitrite are legally labeled for use in the United States, land managers will need to use all of the tools available to help to control wild pig populations. Field trials conducted in Australia showed an 89% reduction and a 63% reduction in wild pig populations using the toxicant (Lapidge et al. 2012). While these trials are promising research is still ongoing, and even when available in the United States there can be no guarantee that the use of toxicants or any other emerging technology will solve the problem.  By observing how successful abatement efforts have been conducted in the past, insight can be gained on developing strategies to implement the tools that are currently available.  And in wild pig management, much like life, timing can be everything. 

Wild pig resources listed below are available at the AgriLife Bookstore

– L-5523 Recognizing Feral Hog Sign

– L-5524 Corral Traps for Capturing Feral Hogs

– L-5525 Box Traps for Capturing Feral Hogs

– L-5526 Placing and Baiting Feral Hog Traps

– L-5527 Door Modifications for Feral Hog Traps

– L-5528 Snaring Feral Hog

– L-5529 Making a Feral Hog Snare

– SP-419 Feral Hogs Impact Ground-nesting Birds

– SP-420 Feral Hog Laws and Regulations

– SP-421 Feral Hogs and Disease Concerns

– SP-422 Feral Hogs and Water Quality in Plum Creek

– SP-423 Feral Hog Transportation Regulations

– L-5533 Using Fences to Exclude Feral Hogs from Wildlife Feeding Stations

– WF-030 Reducing non-target species interference while trapping wild pigs

Click here for additional resources or visit feralhogs.tamu.edu

For free educational programming or technical assistance with wild pigs please contact us:

Josh Helcel, Central and North Central Texas, 512-554-3785, josh.helcel@tamu.edu

Mark Tyson, South and Southeast Texas, 979-845-4698, mark.tyson@tamu.edu

Funding was provided through a Clean Water 319(h) non-point source grant from the Texas State Soil and Water Conservation Board and the U.S. Environmental Protection Agency. Additional funding was contributed by the San Antonio River Authority. Any opinions, findings, conclusions or recommendations expressed are those of the author(s) and do not necessarily reflect the views of the funding agencies.

Literature Cited

Caley, P. and B. Ottley. 1995. The effectiveness of hunting dogs for removing feral pigs (Sus scrofa).
Wildlife Research. 22(2) 147 – 154.

Lapidge, S. J., J. Wishart, L. Staples, K. Fagerstone, T. Campbell, and J. Eisemann. 2012. Development of a feral swine toxic bait (Hog-Gone®) and bait hopper (Hog-Hopper™) in Australia and the USA. Pages 19-24 in Proceedings of the 14th WDM Conference (2012). S. N. Frey (ed).

Muir T.J. and G. Mcewen. 2007. Managing Vertebrate Invasive Species: Proceedings of an international symposium (G. W. Witmer, W. C. Pitt, K. A. Fagerstone, Eds). USDA-APHIS-WS National Wildlife Research Center, Fort Collins, CO.

Parkes, J.P., D.S.L Ramsey, N. MacDonald, K. Waller, S. McKnight, B.S. Cohen and S.A. Morrison

            2010. Rapid eradication of feral pigs (Sus scrofa) from Santa Cruz Island, California.

            Biological Conservation. 143(3): 634-641.

Reidy M.M., T.A. Campbell and D.G. Hewitt. 2008. Evaluation of electric fencing to inhibit feral pig movements. Journal of Wildlife Management. 72: 1012–1018.

Schuyler, P.T., D.K. Garcelon and S. Escover. 2002. Eradication of feral pigs (Sus scrofa) on Santa Catalina Island, California, USA. Turning the tide: the eradication of invasive species. World Conservation Union, Species Survival Commission, Invasive Species Specialist Group. Gland, Switzerland and Cambridge, United Kingdom. 274-286.

Timmons, J. B., J. Rattan, T. Campbell, D. Long,  B. Higginbotham, D. Campion, M. McFarland, N. Dictson, and J. C. Cathey. 2011.  Using Fences to Exclude Feral Hogs from Wildlife Feeding Stations. Texas A&M Agrilife Extension Service. L-5533.

West, B. C., A. L. Cooper, and J. B. Armstrong. 2009. Managing wild pigs: A technical guide. Human-Wildlife Interactions Monograph 1:1–55.