Fact Sheets

Domestic cats (Felis catus) have no native range and are considered an exotic species throughout the world. This species poses a threat to native ecosystems as a reservoir for disease, competitor with other predators, and because of its habit of killing even when not hungry. TWS strongly opposes the existence of feral cat colonies and urges owners to keep their pets indoors or on a leash.

Although many now-extinct horses evolved in North America, feral horses (Equus caballus) today are the descendants of horses introduced to the Americas in the 1500s by Spanish conquistadores. These horses are non-native and damage native ecosystems by trampling vegetation, hard-packing soils, and over-grazing. With no natural predators, horse populations continue to increase and current management options cost taxpayers millions annually.

Feral swine (Sus scrofa) have taken hold in the U.S. as a result of accidental escapes and purposeful releases. Their ability to quickly reproduce and persist under many different habitat conditions has resulted in the species being a degrader of native ecosystems, an agricultural nuisance, and a carrier of disease. Management of this species is particularly difficult, as authority is divided between several different federal, state, and provincial departments with different management priorities.

Bighorn sheep conservation efforts in North America are hampered by the spread of disease.  Domestic sheep and goats grazing on rangelands carry pneumonia and other diseases which can spread to wild bighorn herds and cause mortality events and reduced recruitment into the population.

Lead ammunition and fishing tackle poisons wildlife that inadvertently ingest the substance left behind by hunters and anglers. Bans in the 1990s on the use of lead shot for hunting waterfowl in North America were successful in reducing lead exposure to waterfowl species. However, the continued use of lead tackle and lead ammunition in other hunting pursuits maintains some risk for wildlife. Alternative, non-toxic shot and tackle is available, but their use is not mandated universally, and in some cases, wildlife species are still negatively affected by continued use of lead ammunition and fishing tackle.

Wind energy is one of several renewable energy options that can replace traditional fossil fuel energy sources and reduce greenhouse gas emissions. Wind turbines can also cause direct and indirect impacts to wildlife through collisions, construction activity, and habitat loss and fragmentation.

Wolves once roamed throughout most of North America. Due primarily to conflicts with humans, however, gray wolf (Canis lupus) populations were eradicated throughout much of their historic range. Today, wolf conservation and management continues to be a contentious topic due to human-wildlife conflicts that have resulted from rebounding population numbers in certain regions of the U.S.

Habitat loss and fragmentation can result in many negative impacts for native wildlife populations, such as reducing contiguous habitat area, reducing habitat quality, and isolating populations from one another. Fragmentation occurs when connected natural areas are disjointed by habitat removal, converted to urban or agricultural land, or physical barriers such as fences and roadways are constructed. Habitat fragmentation bisects the landscape and leaves smaller, more isolated land for wildlife, causing local and population level changes to native flora and fauna.