Today, there are areas in the U.S. where the pure Russian wild boar (native to Europe and Asia) can still be found due to importation for sport hunting purposes. However, most feral hogs are from domesticated swine. Feral hogs are wild, but are not a different species than domestic hogs or Russian boars. Webster's dictionary defines feral as having escaped from domestication and become wild. Hence, all feral hogs in the U.S. up until the 1930s were from domestic stock. In a few areas where the Russian boar was imported for sport hunting, escapes have occurred resulting in feral/Russian crossbreeding.
The feral hog has been very successful in expanding its range and increasing in numbers. Its success can be attributed to several factors: free ranging husbandry methods, introduction and re-introduction of feral hogs by hunters, water development in arid areas, improved range condition through better livestock grazing practices, the animal's ability to adapt to a variety of situations and eat a variety of foods, and the hogs' ability to reproduce rapidly. Feral hog populations also have benefited from increased disease control in the domestic livestock industry.
Historically, there are no accurate accounts of feral hog numbers or their distribution in Oklahoma. Like the white-tailed deer, their secretive nature makes it difficult to obtain an accurate count. Statewide distribution is easier to estimate, but is mostly limited to knowledge of their presence or absence in a particular county. During the summer of 2007, Noble Research Institute wildlife and fisheries staff initiated a statewide survey to obtain a better estimate of the distribution and number of feral hogs in Oklahoma. The survey was conducted by wildlife and fisheries intern David Rempe. Agencies surveyed included the Oklahoma Department of Wildlife Conservation, Natural Resources Conservation Service, Oklahoma State University Extension and Oklahoma Department of Agriculture Wildlife Services. Representatives of each of these agencies were contacted in every Oklahoma county and asked if feral hogs were present in the county. If they were, we asked them to estimate density based on three categories: abundant (less than 10 acres per hog), moderate (11-50 acres per hog) or sparse (greater than 51 acres per hog). They were also asked the year that feral hogs were first observed in the county.
Respondents indicated that feral hogs were present in 74 of Oklahoma's 77 counties (Figure 1).
More recent anecdotal evidence suggests that feral hogs are likely present in the remaining three counties. Based on respondent estimates, the feral hog population in Oklahoma was between 617,000 and 1.4 million. The lowest agency estimate of the number of feral hogs in Oklahoma was 430,000 and the highest was 1.6 million. The average low and high estimate for all agencies was 617,000 and 1.4 million, respectively. Density estimates were assigned to mapping grids representing 20 square miles. These grids did not follow river drainages where respondents indicated most feral hogs were located. With inherent mapping error taken into account, the estimated feral hog population in Oklahoma was calculated to be 500,000 or less (Figure 2).
Several variables influenced the estimated year that a feral hog was first present in each county (Figure 3) including the absence of records for first observations, unreported first public sightings and the respondent being new to a county. However, the earliest record of feral hogs in Oklahoma is from the south-central and southeastern portions of the state. It appears that feral hog populations have been spreading across the state from the southeast to the northwest.