Exotic Species and Feral Pigs

• Exotic species are organisms introduced to places they have not previously occupied.
• Introductions can be intentional for aesthetic, economic, and recreational reasons or accidental.
• Exotic species can reach high densities due to the absence of natural predators and diseases.
• Exotic species are responsible for endangering native species and damaging ecosystems.
• Damage and control costs of exotic plants and animals total approximately $137 billion per year.
• Many garden plants, crops, and livestock are exotic species, but the focus is on species that establish wild populations.

Feral Pigs

• Feral pigs were introduced in the 1500s by explorers and settlers for food, with repeated introductions thereafter.
• Feral pig populations exist in over 35 U.S. states, including Hawaii.
• Current feral pig populations exceed 6,000,000.
• Rapid expansion of feral pigs is attributed to human translocations, adaptability to environmental conditions, and a lack of natural predators.

Old World Rats (Rattus sp.)

• Old World rats were accidentally introduced from ships.
• They negatively affected native plants and animals.
• Mongooses were released to control rats, but this caused additional problems for native species.
• Old World rats caused the elimination of several species in the Caribbean.

Chukar Partridge

• The Chukar partridge was introduced from western Asia (Pakistan, Afghanistan, India).
• They were released in 42 US states and 6 Canadian provinces.
• The first successful release occurred in Nevada in 1935, and hunting season opened in 1948.
• They are currently hunted in 10 western states, with Nevada and Utah at the core of the species’ range in the US.
• Their habitat is rugged mountainous terrain in arid and semi-arid regions.
• Introduction failed in portions of NM with similar habitat.
• Cheatgrass (an exotic grass) is important in the diet of the Chukar partridge.
• Chukar partridge occur where few native game birds do.
• They provide sport hunting where native game birds do not occur or have been extirpated because overgrazed rangelands are no longer suitable for sage grouse.

Aoudad (Barbary Sheep)

• Aoudad are native to the Atlas Mountains of northern Africa.
• They were imported for zoos and parks in the eastern US, and their numbers rapidly increased.
• Surplus animals were given to private ranchers for release.
• Wild populations exist in TX, NM, CA, and Mexico.
• An accidental release occurred in CA after escaping from a zoo.
• Intentional introductions occurred in TX and NM.
• In NM, 57 Aoudad were released on state-owned land along the Canadian River after unsuccessful attempts to manage bighorn sheep.
• In Texas, 44 animals were introduced in Palo Duro Canyon in 1957 and 1958 after releases of mule deer appeared to have failed.
• Aoudad compete with mule deer for browse and have greater dietary flexibility than mule deer.
• Aoudad compete with and spread disease to bighorn sheep.
• Bluetongue, a viral disease, is suspected in the absence of bighorn sheep from a portion of their former range.
• Bluetongue is transmitted to bighorn sheep by domestic sheep via insect vectors and is also carried by Aoudad.
• The diet of Aoudad is similar to bighorn sheep.
• 37 of 49 plants important to bighorn sheep are also in the diet of Aoudad.
• Proportion of grasses, forbs, and browse is similar in the diet of both species.

Nutria

• Nutria are aquatic furbearing rodents from South America.
• They were used in commercial fur farming, and animals escaped or were released.
• Wild populations exist in at least 15 states.
• Nutria mature at 6 months and reproduce year-round.
• Nutria destroy wetland vegetation and damage coastal marshes.
• They also damage croplands by cutting sugar cane and corn stalks and consuming other species.
• Nutria girdle trees in orchards, and their burrows damage levees in rice fields.
• Nutria have no significant predators; alligators consume them but do not seem to control populations.
• Nutria are much larger than muskrats, a native species of aquatic rodent, with a weight of 8-10 kg compared to muskrats.