Date of this Version
Hess, S.C., D.H. Van Vuren, and G.W. Witmer. 2018. Feral goats and sheep. pgs. 289-309. In: W.C. Pitt, J.C. Beasley, and G.W Witmer, editors. Ecology and Management of terrestrial vertebrate invasive species in the United States. CRC Press, Boca Raton, FL. 403 pp.
Sheep and goats are among the earliest animals domesticated by mankind (Zeder 2009). Both goats and sheep may have made better candidates for domestication than other animals like deer because they follow a single dominant leader, the herdsman (Geist 1971). They now have a nearly ubiquitous worldwide distribution, and they are among the most abundant of all commensal animals. However, they have also become some of the most widespread invasive feral mammals, particularly on the 100 or more islands throughout the world where they have been introduced, causing severe damage to island ecosystems, in some cases for hundreds of years (Rudge 1984; Chynoweth 2013). Problems caused by feral goats and sheep are a subset of the larger problem of domestic livestock and natural systems. Feral goats are perhaps more widespread than feral sheep because goats have not been as highly modified by the process of domestication (Francis 2015).
The Bezoar ibex (Capra aegagrus) is the most likely ancestor of domestic goats (C. hircus) from both genetic and paleontological evidence (Pidancier et al. 2006). The domestication process started at least 10,000 years ago in highlands of western Iran, beginning with the selective harvesting of subadult males and the transition from hunting to herding of the species (Zeder and Hesse 2000). Multiple independent domestication events may have occurred or domestication may have incorporated multiple ancestral lineages (Pidancier et al. 2006). Traits selected during domestication include behavior, dairy, meat, skins, pelage color, mohair, cashmere, horns, pathogen resistance, and even intestines for catgut. Selection for reduced body size may have been related to the ability to better survive in hot and arid environments (Zeder 2009). A profound reduction in horn size occurred after humans began to control breeding, particularly in males, possibly associated with the absence of selective pressures for large horns used in mate competition (Zeder 2009).