Feral hogs are a significant (and growing) problem for land owners all over the United States. It's tough to determine a precise number, but it's estimated that there are at least 5 million feral hogs present in 39 states. Each year they cause tens of millions of dollars of agricultural damage and have a significant negative impact on the populations of other animals, like white-tailed deer and ground-nesting birds.

Though they've quickly adapted to live in the United States, feral hogs are actually an invasive species introduced by explorers and settlers in the 1500s and 1600s. Since they are prolific breeders and don't have many natural predators, feral hog populations have grown rapidly.

Hogs become sexually mature when they're around a year old and can produce two (and sometimes three) litters of up to eight piglets per year when food is plentiful. Add a few hogs that escaped from farms as well as those specifically introduced to new areas by hunting outfitters, and it's easy to see how the feral hog population exploded and spread across the country like wildfire.

Feral hogs are omnivorous and will eat pretty much anything they come across, especially acorns and agricultural crops. Using their tusks, they root up the ground in order to eat roots and bugs. Because of this, a few hogs can absolutely destroy a farmer's field overnight. They will also kill and eat just about any animal they can catch, such as snakes and even fawns.

In addition to all of this, feral swine are pretty darn smart animals. With an intelligence level that rivals that of dogs, they might even be smartest game animal in the United States. Their sense of smell is incredible, and they have good eyesight and hearing.

All of these things combine to make them a worthy foe and a difficult animal to eradicate from an area once they get established.

The spread of wild pigs in the United States. This map illustrates cumulative documented occurrence of wild pigs from 1982 to 2012 based on Southeastern Cooperative Wildlife Disease Study (SCWDS) records. Image: Conservation Science Partners.

Fortunately, most states have pretty liberal hog-hunting regulations. Seasons, if they even exist, are usually long with large (or unlimited) bag limits. The rules vary from state to state, but trapping is often legal, as is hunting over bait, hunting at night and hunting them with dogs.

Hunters kill tens of thousands of hogs each year. Though most of these hogs are killed by chance while hunting deer, many hunters specifically target hogs. They are fun to hunt and, when handled and cooked properly, their meat is safe to eat and tastes delicious.

However, hogs are intelligent and resilient animals. They will quickly change their habits such as feeding primarily at night in response to hunting pressure. Since they reproduce so rapidly, 70 percent of the hog population must be killed each year just to keep their numbers from increasing.

With this in mind, it should be obvious that it's virtually impossible to control the hog population through hunting alone.

More aggressive hog control methods — hunting them with hounds, hunting them at night, trapping them or even shooting them from a helicopter can really put a dent in a local hog population. However, unless it is part of a comprehensive hog control strategy carried out over a large area, these measures usually only deal with the hog problem temporarily. Over time, the hogs return like nothing ever happened.

So, what can we do about the feral hog problem? Unfortunately, there is no easy answer to that question.

The first thing we need to do is to stop making the problem worse by allowing hunting outfitters to transport and introduce hogs to areas where they don't already live. Hunting and trapping certainly have their place, but they aren't enough to control an out-of-control hog population by themselves. For this reason, scientists are looking at several different ways to control hog numbers through contraceptives and poison.

They're still doing research on the subject, but sodium nitrate poison is looking promising. The Australians have used it with a fair amount of success on their hog population for years, and it's being tested on feral hogs in Texas as we speak. Their initial findings indicate that it is effective at killing hogs and seems to present little risk to other animals, primarily scavengers.

Only time will tell if it will work on a large scale. Until then, keep doing your part in the fight against feral hogs by hunting and trapping them.

For more about the hog problem in America, see Part II here.