The feral goat is the domestic goat (Capra aegagrus hircus) when it has become established in the wild. Feral goats occur in Australia, New Zealand, Ireland, Great Britain, Hawaii, Brazil, Honduras, Lebanon, Panama, Madagascar, Comoro Islands, Mauritius, Réunion, Irian Jaya, Papua New Guinea, the Galapagos, Cuba and in many other parts of the world. When feral goats reach large populations in habitats which are not adapted to them, they may become an invasive species with serious negative effects, such as removing native scrub, trees and other vegetation. However, in other circumstances they may become a natural component of the habitat, even replacing locally extinct wild goats. Home range use and movement patterns of non-native feral goats in a tropical island montane dry landscape. Feral goats are sometimes used for conservation grazing, to control the spread of undesirable scrub or weeds in open natural habitats such as chalk grassland and heathland.
Goats were first introduced into Australia in 1788. Since then they have become feral and are now causing an estimated economic loss of $25 million per year as well as environmental degradation.
The Kri-kri (also called the "Cretan goat", "Cretan Ibex," or "Agrimi") was previously considered a subspecies of wild goat but has recently been identified as a feral variety of the domestic goat. The Kri-kri is now found only on the island of Crete, Greece and three small islands just offshore. There are rumours among the locals of these islands that this goat, is in fact, venomous, although there is not yet any confirmation of these claims.
The balearean boc is a feral goat introduced in Majorca island since neolithic period. It is perfectly adapted to the island ecosystem, and occupies a similar ecological niche that the extinct myotragus had. The "boc balear" is considered a game species. The biggest threat to their conservation in hybridization with current domestic goats, but both are the same specie (Capra aeagrus hircus). These populations threaten the recruitment of several forests in the island, specially oak forests.
Descendants of Neolithic goats have inhabited the Cheviot Hills of Northumberland for more than five thousand years.
Feral goats have caused serious damage to native vegetation on the Galapagos archipelago. The goats first made an appearance on the island of Pinta in 1959, when fisherman brought three goats with them to the Galapagos. By the 1970s, three goats grew to 40,000 and an intervention was needed. Goats destroyed the native species' habitats, spread invasive plants through their excrement (such as the blackberry bush), and wreaked havoc on the island's delicate ecosystem.
In 1999, the government retaliated with Project Isabela: a three-stage plan put in place in order to eradicate goats on the islands. Stage 1 of the plan was called Ground Hunting. The government offered cash awards to locals who would hunt goats. This stage backfired, however, as the locals began breeding the goats in order to make more money. Stage 2 of Project Isabela was called Aerial Attacks. Professional hunters from New Zealand flew in on helicopters and gunned down thousands of goats at a time from the sky, wiping out nearly the rest of the goats on the islands. Stage 3 was called Judas Goats. Female goats were sterilized and given a hormone treatment to be in heat constantly and released. When the females would attract a male, the male goat was then killed on sight. The goat corpses were left where they were killed to rot and restore important nutrients to the soil.
Project Isabela was a huge success, eradicating goats on the islands of Isabela, Pinta, and Santiago by 2006.
Feral goats are common in many areas of the Irish west coast including counties Mayo, Donegal and Kerry. In the town of Killorglin, in County Kerry, Puck Fair takes place each year in which a wild goat is captured and crowned "King" of the fair, in a continuation of ancient Celtic practices. The Bilberry Goats are feral goats living on Bilberry Rock in Waterford City, along with the Irish Goat, which is not actually native to Ireland. In the Wicklow mountains NP feral goats can be seen in the surroundings of Glendalough.
Feral goats, introduced in 1574, had become a plague in the Juan Fernández Islands.
The Arapawa Island goat is a breed of feral goat found only on Arapaoa Island. Auckland Island goats were extirpated in the wild in the late 20th century. The New Zealand feral goat is the descendant of many breeds of goat, such as Angora, Kiko, Spanish, Pygora, Boer, Saanen, Nubian and Alpine.
Feral goats are a fairly common sight in the Scottish Highlands. The goats are descendants of livestock abandoned, through necessity, by Highlanders during the Highland Clearances. The goats act as a living reminder of the region's turbulent past.
The San Clemente Island goats were a feral species that arrived in 1875 on San Clemente Island from Santa Catalina Island, both off the coast of California. They remained isolated there until several were adopted out to become domesticated on the mainland in the United States and western Canada. The US Navy was given the right to exterminate the last remaining feral goats on San Clemente Island in 1991. They are genetically related to Iberian goats, though their isolation has caused enough genetic drift to make them distinct from goats now in Spain and other Spanish goats in the United States. The Livestock Conservancy considers them a critically endangered heritage breed. In 2008, their global population was approximately 400; all now domesticated. The Goats' bleat is so consistent that it is sometimes confused with a recorded goat sound.
Feral goats occur in the Welsh mountains. They are used for conservation grazing in a number of places, such as at Stackpole in South Wales or on Great Orme in Llandudno in North Wales.