Ovis aries
mouflon

Domestic sheep live worldwide in association with humans. The first domesticated sheep resided mainly in the Middle East and Central Asia but since then have been introduced everywhere.

Domestic sheep are extremly versitile and exist in a wide variety of habitats worldwide ranging from temperate mountain forests to desert conditions. (Grzimek 1990, MacDonald 1984)

The physical details of domestic sheep vary greatly among breeds. Head and body length is 1,200-1,800 mm and shoulder height is 650-1,270 mm. Female sheep tend to be three quarters to two thirds the size of males. Wild sheep have tails between 70-150 mm but in domestic sheep tails may be larger and used as a fat reserve, although these long tails are removed on most commercial farms. Sheep have a vertical cleft and narrow snout completely covered with short hair except on the margins of the nostrils and lips. The genus Ovis is characterized by the presence of glands situated in a shallow depression in the lacrimal bone, the groin area, and between the two main toes of the foot. These glands secrete a clear semi-fluid substance that gives domestic sheep their characteristic smell. The skulls of domesticated sheep differ from those of wild sheep in that the eye socket and brain case are reduced. Selection for economically important traits has produced domestic sheep with or without wool, horns, and external ears. Coloration ranges from milky white to dark brown and black. There is considerable diversity among the over 200 distinct breeds of sheep. For details on a specific breeds consult http://pc200.anmsci.okstate.edu/BREEDS/SHEEP.

Ovis aries has a highly developed flocking or herding instinct. Large groups of sheep (up to 1000 or more) move over an area in groups, rather than as individuals. No "leaders" in the flock initiating grazing or other forms of behavior, including flight. This flocking instinct contributes to their economic significance as a single shepherd can control a large flock of animals. Sheep become considerably stressed when separated from others, often calling and pawing at the ground.

Sexual behavior in Ovis aries is important in sheep production. Mating occurs mainly in the early morning or in the evening. Rams search for ewes and if a ram suspects the ewe is in estrus, he will nudge the ewe in the perineum. The ewe then assumes a mating stance if interested in the ram or walk away if not. If the ewe is interested the ram will conduct a short "foreplay" session, mount and copulate. If not then he will move on to another ewe. (Hecker 1983)

Domestic sheep are extremely hardy animals and can survive on a diet consisting of only cellulose, starch or sugars as an energy source and a nitrogen source which need not be protein. In general, sheep feed mainly on grasses while in pastures and can be fed a wide variety of hays and oats. Considerable research has been done on sheep nutritional requirements, and feed substitution tables are present in Ensminger's 1965 "The Stockman's Handbook". Grazing sheep ingest a large amount of food in a short time, then retire to rest and rechew the ingested matter. Sheep spend their day alternating between these periods of grazing and ruminating. Ovis aries has a large and complex stomach which is able to digest highly fibrous foods that can not be digested by many other animals. Its modest nutritional requirements contribute to its economic significance.(Hecker 1983, Ensminger 1965)

Ovis aries has no adverse effects on human populations. The proliferation of domestic sheep, though, has adversely effected populations of their wild relatives through competition for forage and the spread of disease.

Ovis aries is one of the most economically significant species on the planet. Since their domestication between 9000 and 11000 years ago they have been a source of meat, milk, wool and hides in nearly every country. In some cultures sheep are considered highly useful as a sacrificial animal. The versatility of the species contributes to its economic significance as large herds of animals can be maintained in many environments at relatively low costs. Besides their usefulness in an agricultural sense, sheep have become important as a tool for scientific research. Because of their large size and low maintenance costs they make an ideal model for a great deal of scientific research.

The world population of domestic sheep has steadly increased since their domestication and the world sheep population totals over a billion sheep.

There is considerable controversy over when and from what wild species the first domestic sheep descended. Current chromosomal and archeological evidence indicates that the divergence occurred about 9000-11000 years ago and that the first sheep domesticated were from the mounflon (Ovis musimon) flocks from Sardinia and Corsica. (Grzimek 1990)