By:
Mark Tyson, M.S., Extension Associate
James Cash, Student Assistant
J. Matt Wilkins, Student Assistant
The feral hog (Sus scrofa) is quickly becoming one of the most prolific
invasive, exotic species known to occur in Texas. Land managers have been
dealing with them for many decades; however, populations have notably increased
across the state since the 1980s. Like the hogs themselves, technology aimed at
reducing feral hog populations is greatly expanding. New innovations such as
remotely triggered trap gates and specially designed snares show great promise
as population reduction tools. Another innovation that has gathered much
attention is the feral hog toxicant, sodium nitrite. KEEP IN MIND THAT THERE ARE NO APPROVED TOXICANTS FOR USE ON FERAL HOGS! Is there a sodium solution
to our state’s growing feral hog problem? Join us on an exploration of this
potential pig poison.
Feral hog (Sus scrofa)
One of the more common questions we receive concerning feral
hogs is, “When is that feral hog poison going to be available?” We are quick to
point out that it is currently illegal
to use any type of poison, toxicant or chemical compound on feral hogs in Texas.
This “poison” is formally known as sodium nitrite and is commonly used as a
preservative in processed meats. Ignore that light bulb that just went off in
your head. While you can purchase this meat preservative, any attempt to poison
pigs with it would be both illegal and in vain. The compound’s rapid oxidation
and strong odor present palatability issues that deter consumption of lethal
doses by feral hogs. Thus, research efforts continue to investigate more
favorable formulations for delivery to feral hogs.
You may be wondering why there is so much interest in this
toxicant. When dealing with feral hogs you quickly learn that they are highly
intelligent and adaptable. You can gain additional insight into their behaviors
by reading Feral
Hogs Adaptable, Efficient and Effective. Current legal methods for
controlling feral hogs in Texas include trapping, shooting, snaring and the use
of trained dogs. While each of these techniques have their place in a feral hog
management plan, they each require varying investments of time and effort while
yielding varying levels of hogs harvested. Additionally, these legal methods
are often focused at the sounder level within a specific area. The use of a
toxicant would offer land managers a technique that could be implemented on a
multi-sounder scale across large areas of land.
So how exactly does this compound work? Sodium nitrite
causes death through the process of methemoglobinemia. In this process the
component of the blood that normally carries oxygen, called hemoglobin, is
oxidized (changed) into methemoglobin.
Methemoglobin does not operate the same as hemoglobin and cannot
transfer oxygen throughout the body. Without oxygen being transferred to vital
organs, the hog will soon die. Humans and many other animals produce
methemoglobin reductase which can reverse moderate methemoglobinemia, however
swine do not produce methemoglobin reductase in significant amounts, so they are
vulnerable to poisoning via sodium nitrite (Cowled et al. 2008). Death takes
place between 1 to 1.5 hrs after consumption of the toxicant (Lapidge et al.
2012). This method of toxicosis is considered a swift, humane method of swine
control (Lapidge et al. 2012). Another common question associated with the use
of sodium nitrite is what is the risk of secondary poisoning through
consumption of deceased hogs by predators or humans? Three factors make
secondary poisoning unlikely. The half-life
of nitrite plasma is roughly 30-60 minutes in dogs, horses, rats, sheep, and
humans, which means that sub-lethal doses in the body are quickly reduced
(Lapidge et al. 2012). It is unlikely, while eating meat from a poisoned hog,
to ingest the high amount of nitrite in the short amount of time necessary for
a fatal dose. Also, a large percentage
of the nitrite that is ingested by the hog is converted to another compound
during the methemoglobinemia process.
Where has this toxin been used? Is there any scientific data
supporting the use of this product?
These are all valid questions when considering the use of sodium nitrite
as a tool for feral hog control.
Biologists in Australia have run a number of tests in controlled
environments on the use of this substance.
Two specific field trials concluded that an 89% reduction and a 63%
reduction in the population of feral hogs was achieved (Lapidge et al. 2012). These
statistics have grabbed the attention of international biologists when it comes
to managing feral hog populations. In
fact, biologists in the state of Texas have begun to research the use of sodium
nitrite as a potential method of reducing feral hog populations. Over the past three years Texas Parks and
Wildlife (TPWD) biologists have researched the use of sodium nitrite at the
Kerr Wildlife Management Area (WMA).
Biologists of the National Wildlife Research Center (NWRC) have also
begun to research the effects of the use of sodium nitrite as a feral hog
management option. NWRC biologists have
even gone as far to say that, “Sodium nitrite may be the Achilles Heel” of
feral hogs (Cowled et al. 2008).
Louisiana State University has also begun working on a strategy for
implementing sodium nitrite as a poison for feral hogs.
By now I’m sure you are thinking, so when is this new tool
going to be available for use by the public? The answer “it depends” would most
likely be the best one I could give. The
public debut of sodium nitrite as a feral hog toxicant truly depends on many
factors. Researchers are currently facing a few speed bumps on the road to
success. These speed bumps include creating a stable formulation that is
consistently palatable to the hogs, deterring non-target species from consuming
lethal doses, and many challenges that yet remain unseen. While this compound
most likely will not be available to the public for several more years, it does
show great promise as a feral hog management tool. Harry S. Truman once said, “America
was not built on fear. America was built on courage, on imagination and an unbeatable
determination to do the job at hand”. I have great faith in America’s
courageous, imaginative and determined researchers and wildlife managers, and
in time, sodium nitrite will become yet another tool available in the war on
feral hogs.
The hyper-linked resource document below will provide you with quick access to many of our online feral hog resources including publications, fact sheets and videos.
Literature Cited
Cowled,
B. D., P. Elsworth, and S. J. Lapidge. 2008. Additional toxins for feral pig
(Sus scrofa) control: identifying and testing Achilles’
heels. Wildlife Research 35: 651–662
Lapidge,
S, J., and C.T. Eason. 2010 Pharmacokinetics and methaemoglobin reductase
activity as determinants of species susceptibility and non-target risks from
sodium nitrite manufactured feral pig baits. Report for the Australian
Government Department of the Environment, Water, Heritage and the Arts.
Canberra, Australia.
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).