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 breeds on a seasonal basis, determined by day length, with females (ewes) first becoming fertile in the early fall and remaining fertile through midwinter. Estrus cycles range between 14 and 20 days with 17 as the average. Females are in heat on average for 30 hours. Males (rams) are fertile year round and most domestic sheep breeders use 1 ram to 25 to 35 ewes. Gestation averages 148 days with most lambs born in mid spring. One or two lambs, which are able to stand and suckle within a few minutes of birth, are born to each ewe. Both male and female lambs reach sexual maturity within one year. (Ensminger 1965)
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 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.
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.
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)
Chris Reavill (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.
uses smells or other chemicals to communicate
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates
animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.
A substance that provides both nutrients and energy to a living thing.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
referring to animal species that have been transported to and established populations in regions outside of their natural range, usually through human action.
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.
found in the oriental region of the world. In other words, India and southeast Asia.
scrub forests develop in areas that experience dry seasons.
reproduction that includes combining the genetic contribution of two individuals, a male and a female
one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.
associates with others of its species; forms social groups.
uses touch to communicate
A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in temperate latitudes (>23.5? N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.
"Breeds of Livestock" (On-line). Accessed Oct. 14, 1999 at http://pc200.anmsci.okstate.edu/BREEDS/SHEEP/.
Ensminger, M. 1965. The Stockman's Handbook. Danville, Illinois: The Interstate.
Grzimek, B. 1990. Grzimek's Encyclopedia of Mammals. NY: McGraw-Hill.
Hecker, J. 1983. The Sheep as an Experimental Animal. London: Academic Press.
Lydekker, R. 1912. The Sheep and Its Cousins. London: George Allen & Company.
MacDonald, D. 1984. Encyclopedia of Mammals. NY: Facts on File Publications.