Like most nonnative, invasive species, feral swine (Sus scrofa) in the United States has an increasingly negative impact on native plants. If left unchecked, feral swine will become responsible for the permanent destruction of many plant communities as well as endangering native plant populations.
Nonnative species can also be called alien, exotic, or nonindigenous. Their presence is due to humans dispersing them to other locations beside their native habitat, or by humans creating environmental conditions that allow their growth. When nonnative species begin to take over a new habitat and displace native species, they are then termed an invasive species. Nonnative invasive species are one of the biggest threats to ecosystems in North America (Cox, 1999) because they are able to have an impact on many levels, including ecosystems, communities, and populations (Cushman, Tierney, & Hinds, 2004).
Feral swine are considered to be in the top 100 problematic invasive species. Sus scrofa are native to Eurasia and North Africa, but are currently found on all continents except Antarctica (Timmons et al, 2012). Swine arrived in North America in 1493. Escaped domestic swine were the first to begin the feral swine population, and when settlers first arrived, there continued to be an increase in escaped pigs. Hunters would intentionally release swine to build up sport hunting. Many of these released swine were domesticated European wild boar mixes (Kaller & Kelso, 2006).
Swine are omnivores that have a varied diet consisting of invertebrates, fungi, acorns, roots and bulbs found in the soil (Cushman, Tierney, & Hinds, 2004). The majority of the swine’s diet consists of plant forage, with native plants being preferred. They do eat other animals, including earthworms, arachnids, birds, and mammals (Mayer & Brisbin, 2009). Feral swine are food generalists, as well as habitat generalists, so they adapt well not only to consuming different foods, but also to varying biomes (Bratton, 1975). This flexibility to many different plants for food is a major reason that the feral pigs are so invasive.
Another major reason for this species invasiveness is due to the fact that they have a high reproductive rate (Bratton, 1975). Males can breed year-round and females go into heat every 18-24 days, with fertility lasting from 2-3 days. The gestation period (time of pregnancy) is an average of 112-120 days. About one week after giving birth, the females will again go into heat (Mayer & Brisbin, 2009). The litters consist of about 4-6 young born (Timmons et al, 2012). This shows how easily it is for the feral swine population to increase drastically in one year because females can have two or more decent-sized litters in a year.
Rooting is the way that swine forage for food. It usually occurs as small patches (about a square meter) of disturbed areas (Timmons et al, 2012). Rooting digs soil up from 5cm to 15cm in depth, and soil dug up are sometimes pushed to the side...