Thought to number up to 50 million when Europeans first arrived in South America (2) (3) (9), the guanaco has since undergone a steep decline, particularly during the last century, and now numbers fewer than 600,000 individuals, 90 percent of which are found in Argentina. Although still relatively widely distributed, the guanaco now occupies only 40 percent of its original range, and has become fragmented into often small and relatively isolated populations, increasing the risk of local extinctions in some areas (1) (9). L. g. cacsilensis is the more threatened subspecies, numbering perhaps fewer than 3,000 individuals, in small, isolated populations (9).
Major threats to the guanaco include overhunting, for skins, meat and wool, as well as poaching, habitat degradation, and the fragmentation and isolation of its populations due to development and the use of barbed wire fences. Overgrazing and drought, possibly linked to climate change, pose further threats to its habitat (1) (6) (9). The large decline in guanaco numbers in the last century is thought to largely result from the introduction of domestic sheep, which monopolise the best feeding areas and compete with the guanaco for food (1) (9) (10). Sheep breeders often kill the guanaco, viewing it as a competitor with sheep and a possible source of disease transmission (2) (6) (9), although it has been suggested that the diseases of domestic livestock are likely to threaten the guanaco rather than the other way around (1) (11).