Capra aegagrus pseudohircus

[…] But currently, the most serious case of pastoral imposture afflicting UK farms is that of the False domestic ibex (Capra aegagrus pseudohircus).

They arrive on the scene in packs of about five, and insinuate themselves into a proper herd of goats with little initial violence.

The males work together to remove the native alpha bucks, either driving them away or killing them. They will often trample newborns.

This alien threat can dominate and even completely replace a herd of domestic goats in a space of six months. Very frequently, the minder detects nothing of the invasion until it is too late.

Rather than face economic ruin, farmers are likely not to report an infestation, and instead attempt to pass off their herd as genuine. Consumers of the resulting wool, meat and milk often fail to notice a difference, exacerbating the problem.

False domestics are thought to originate from the South Caucasus. They most closely resemble the common British Alpine breed. Telltale differences include a beard several millimetres shorter than average, particularly dense horns and (reportedly) ranker odour than usual.

From: Khabilla Simmic, “Key players in the growing invasive livestock problem”, BBC News (30 October 2008). Retrieved on 2008-10-30.