Feral pig
A feral pig is a domestic pig which has gone feral, meaning it lives in the wild. The term feral pig has also been applied to wild boars, which can interbreed with domestic pigs.[1] They are found mostly in the Americas and Australia. Razorback and wild hog are Americanisms applied to feral pigs or boar–pig hybrids.
"Razorback" redirects here. For the whale species, see Fin whale. For other uses, see Razorback (disambiguation).Definition
A feral pig is a domestic pig that has escaped or been released into the wild, and is living more or less as a wild animal, or one that is descended from such animals.[2] Zoologists generally exclude from the feral category animals that, although captive, were genuinely wild before they escaped.[3] Accordingly, Eurasian wild boar, released or escaped into habitats where they are not native, such as in North America, are not generally considered feral, although they may interbreed with feral pigs.[4] Likewise, reintroduced wild boars in Western Europe are also not considered feral, despite the fact that they were raised in captivity prior to their release.
Hawaii
A genetic analysis found that the first pigs were introduced to Hawaii by Polynesians in approximately AD 1200.[36] Additional varieties of European pigs were introduced after Captain Cook's arrival into Hawaii in 1778,[37] where they prey on or eat endangered birds and plants. The population of feral pigs has increased from 2 million pigs ranging over 20 states in 1990, to triple that number 25 years later, ranging over 38 states with new territories expanding north into Oregon, Pennsylvania, Ohio, and New Hampshire. Some of these feral pigs have mixed with escaped Russian boars that have been introduced for hunters since the early 1990s.[38]
Feral pigs are opportunistic omnivores, with about 85%-90% of their diet being plant matter, and the remainder animal.[22] Plants have difficulties regenerating from their wallowing, as North American flora did not evolve to withstand the destruction caused by rooting pigs, unlike European or Asian flora.[39] Feral pigs in the U.S. eat small animals, mostly invertebrates like insects and worms but also vertebrates such as wild turkey poults, toads, tortoises, and the eggs of reptiles and birds.[40] This can deprive other wildlife that normally would feed upon these important food sources.
In some case, other wildlife are out-competed by the feral pigs' higher reproductive rate; a sow can become pregnant as early as six months old and give birth to multiple litters of piglets yearly.[22] In the autumn, other animals such as the American black bear compete directly with feral pigs as both forage for tree mast (the fruit of forest trees).[41] These are likely reasons that they reduce diversity when they invade.[12]
In the U.S., the problems caused by feral pigs are exacerbated by the small number of species which prey on them. Predators such as bobcats and coyotes may occasionally take feral piglets or weakened animals, but are not large enough to challenge a full-grown boar that can grow to three times their weight. In Florida, feral pigs made up a significant portion of the Florida panther's diet.[42] Other potential predators include the gray wolf, red wolf, cougar, jaguar, American alligator, American black bear, and grizzly bear. Unfortunately, each keystone predator presents problems: the jaguar is extirpated from California and the Southwest. The grizzly bear, while native to most of the American West, is gone from the states that have large feral pig populations, namely Texas, Arizona, California, and New Mexico; and the species also has a very slow reproductive rate. Wolf numbers are small and expected to remain so as they slowly repopulate their range; only a few individuals thus far have been recorded as inhabiting California, in spite of thousands of square miles of good habitat. The cougar is present in most of the West, but is gone from the East, with no known populations east of Minnesota in the north, and very thin numbers east of Houston in the South. The American black bear is both predator and competitor, but in most areas probably may not impact feral pig populations enough to control them. Programs do exist to protect the weakened numbers of large predators in the U.S., but it is expected to take a very long time for these animals to naturally repopulate their former habitat.[43]
South America
In South America, during the early 20th century, free-ranging boars were introduced in Uruguay for hunting purposes and eventually crossed the border into Brazil in the 1990s, quickly becoming an invasive species. Licensed private hunting of both feral boars and their hybrids with domestic pigs was authorized from August 2005 on in the southern Brazilian state of Rio Grande do Sul,[44] although their presence as a pest had been already noticed by the press as early as 1994.[45] Releases and escapes from unlicensed farms (established because of increased demand for boar meat as an alternative to pork) continued to bolster feral populations and, by mid-2008, licensed hunts had to be expanded to the states of Santa Catarina and São Paulo.[46]
Recently established Brazilian boar populations are not to be confused with long-established populations of feral domestic pigs, which have existed mainly in the Pantanal for more than 100 years, along with native peccaries. The demographic dynamics of the interaction between feral pig populations and those of the two native species of peccaries (collared peccary and white-lipped peccary) is obscure and is still being studied. The existence of feral pigs could somewhat ease jaguar predation on peccary populations, as jaguars show a preference for hunting pigs when they are available.[47]
Fatal attacks on human beings
Feral pigs can be dangerous to people, particularly when the pigs travel in herds with their young, and should be avoided when possible. Feral pigs living in the United States have been known to attack without provocation and fatally injure human beings. There have been over 100 documented attacks by feral pigs on human beings in the United States between the years 1825 and 2012. Of these attacks, five have been fatal. Three of the five fatal attacks were by feral pigs wounded by hunters. Both male and female feral pigs are known to attack without provocation, and attacks by solitary males, as well as group attacks have been documented.[52][53][54]
On November 26, 2019, a 59-year-old Texas woman named Christine Rollins was attacked and killed only a few feet away from the front door of her workplace by a herd of feral pigs in the town of Anahuac, Texas, which is 50 miles east of Houston. This incident was the fifth documented fatal feral pig attack in the United States since 1825.[52] Chambers County Sheriff Brian Hawthorne in a formal statement to news media stated that "multiple hogs" assaulted Rollins during pre-dawn hours between 6 and 6:30 a.m. when it was still dark outside. The victim died of blood loss as a result of her injuries.[55]