In ideal conditions, a population of wild pigs can double in just 4 months, but more typically, the annual growth rate in populations of feral hogs is about 20%. Feral hogs may begin to breed before 6 months of age if they have a high-quality diet. Sows usually have 1 litter per year although 2 litters per year is possible, and young may be born at any time of the year. Litter size depends upon the age of the sow, nutritional intake, and time of year. Litters of feral hogs average 3 to 8 young, but have ranged up to 13. Wild boars usually breed at 18 months.
Wild pigs seek water and dense vegetation when temperatures are high. When the weather turns cold, they pile grass and leaves high enough to bury themselves for warmth.
Wild pigs are intelligent and adapt readily to changing conditions. They may rapidly modify their responses to humans. Wild boars have a greater capacity to invade colder and more mountainous terrain than do other wild pigs. Feral pigs are social and form family groups called “sounders.” A sounder consists of 1 or more sows and their offspring. Male pigs tend to be solitary. The home range of wild pigs depends on the availability of food, but typically consists of 0.3 to 3 square miles.
During hot weather, or if hunting pressure is great, wild pigs remain in the shade in wallows during the day and feed at night. Wild pigs cool themselves in wallows by rolling in mud and then use trees or posts, called rubs, to scrape off the mud. In cold weather they feed during the warmest parts of the day.
Pigs possess many biological and behavioral traits that enable them to live just about anywhere and quickly populate new areas. A variety of habitats, from tidal marshes to mountain ranges, are suitable for wild pigs. They prefer the cover of dense brush or marsh vegetation (Figure 4). In generally, they are restricted to areas below snowline and above freezing temperatures, but populations are expanding northward in the US and Canada including areas that have subzero temperatures. Wild pigs frequent livestock-production areas.
Wild pigs are omnivores. Types of food vary greatly depending on the location and time of year, but plants make up about 85% of their diet. Acorns or other mast, when available, make up a good portion of the diet. Wild pigs gather in oak forests when acorns fall and generally do not wander far from the forest during this period. In the winters of poor mast years, wild pigs increase their range and consume greater quantities of underground plant material, herbaceous plants, and invertebrates (worms and insects). They may feed on underground vegetation during wet weather or in areas near streams and underground springs. Wild hogs ingest flesh from vertebrates and prey on bird eggs, but the extent to which animals are taken as prey or carrion is not fully known. Given food, water, and cover, wild pigs can live almost anywhere.