Sheep (Ovis aries): Facts, Wool, Breeds and Lifespan

Where do sheep come from?

Sheep belong to the subfamily Caprinae, which also includes goats, ibex and musk oxen. The genus Ovis contains several wild sheep, among them the mouflon of the Middle East, the argali of Central Asia and the bighorn sheep of North America.

The domestic sheep descends from the Asiatic mouflon (Ovis gmelini), a reddish-brown wild sheep that still lives in parts of Turkey, the Caucasus and Iran, and is listed as Near Threatened by the IUCN. Domestication began roughly 11,000 to 10,500 years ago in a region stretching from southeastern Anatolia to the northern Zagros Mountains. From there, sheep spread with early farmers into Europe, Africa and South Asia. The mouflons of Corsica and Sardinia, once thought to be truly wild, are now known to be feral descendants of these early domestic sheep.

Early domestic sheep were hairy rather than woolly. Breeding for a soft, continuously growing fleece came thousands of years later, and the earliest woven wool garments date to about 6,000 years ago.

Appearance

Sheep are stocky, short-tailed grazing animals with split hooves. Most breeds are white, because white wool is easy to dye and the gene for white fleece is dominant, but sheep also come in black, brown, gray, spotted and the dark-faced patterns of many British hill breeds.

Horns vary by breed. In some breeds both sexes are horned, in others only the rams, and many modern breeds are naturally hornless. A ram’s horns grow in a spiral and can become massive. The Jacob sheep can carry four or even six horns.

Sheep have horizontal, rectangular pupils and eyes on the sides of the head. In breeds without much wool on the face, their field of vision reaches roughly 270–320 degrees, so a sheep can watch almost all around itself while grazing. Their upper lip is split, which lets them nip grass very close to the ground.

How big is a sheep?

Size depends heavily on breed. Small primitive breeds are about the size of a medium dog, while big meat rams can weigh more than a large man.

Rams are larger than ewes in every breed, and in the heaviest breeds can exceed 130 kg (290 lb). Head-and-body length in most breeds is about 1.2–1.8 m (4–6 ft).

Wool and hair

A sheep’s fleece is made of wool, a crimped, springy fiber of keratin, the same protein found in hair and fingernails. Wild sheep grow a coat of coarse outer hair, called kemp, over a short woolly undercoat that falls out each spring. Thousands of years of breeding replaced the kemp in most breeds with a soft wool coat that keeps growing all year.

That is why most domestic sheep must be shorn at least once a year. Wool is still the most widely used animal fiber in the world. Fine-wool breeds such as the Merino, developed in Spain and now dominant in Australia, produce very soft fiber for clothing, while long-wool and carpet-wool breeds produce stronger, coarser wool. Hair sheep, such as the Dorper and Katahdin, grow a coat that sheds naturally and are kept for meat. The full story is in Why do sheep need shearing?.

Diet and grazing

Sheep are herbivores and mostly grazers. They prefer grasses, clover and other short, leafy plants and usually avoid the woody shrubs that goats readily browse. Because they bite so close to the ground, sheep can overgraze a pasture faster than cattle, so many farmers rotate flocks between fields.

Like cattle and goats, sheep are ruminants with a four-chambered stomach. They graze quickly, then lie down to bring food back up and chew it again as cud, while microbes in the rumen break down the tough plant fiber. Adult sheep have no upper front teeth: their lower incisors bite against a hard dental pad in the upper jaw.

Behavior and flocking

Sheep are strongly social prey animals. They stay close together, and a flock tends to follow whichever animal moves first. This instinct protects them from predators and also made sheep easy for early people to herd. Sheep separated from their flock become visibly stressed and call for their companions. Why the flock moves as one is explained in Why do sheep follow each other?.

On open hills, flocks learn their home ground. In the Lake District and other British uplands, ewes pass knowledge of their own patch of unfenced fell, called the heft, to their lambs, so each flock stays on its traditional grazing without fences.

Sheep are smarter than their reputation suggests. A study by Keith Kendrick and colleagues found that sheep could remember the faces of 50 other sheep for over two years, and later experiments taught sheep to recognize photographs of human celebrities. More examples are in Are sheep smart?.

Sheep communicate by bleating, and each ewe and her lamb learn to recognize each other’s calls. Rams compete in the breeding season by charging and clashing heads.

A heavily fleeced sheep that rolls onto its back in a hollow can sometimes get stuck, unable to turn over. Shepherds call this a “cast” sheep, and it is one reason upland farmers check their flocks often in late spring, when fleeces are heaviest.

Reproduction and life cycle

Most sheep from temperate regions are seasonal breeders. Shortening days in autumn bring ewes into season, and lambs are born in late winter or spring. Pregnancy lasts about five months, roughly 147 days. Single lambs and twins are most common, and some breeds, such as the Finnsheep, often have triplets or more.

Lambs are born well developed and usually stand within an hour of birth to drink their mother’s first milk. A ewe recognizes her own lamb by smell and voice. Young sheep are called lambs until about a year old; on British farms a sheep between weaning and its first shearing is often called a hogget.

How long do sheep live?

A sheep that is not slaughtered commonly lives about 10–12 years, and some reach about 20. The AnAge database records a maximum of about 22 years. Many sheep live far shorter lives on farms: lambs raised for meat are usually slaughtered at a few months to a year old, and breeding ewes are often sold when their teeth wear down at around five to seven years. See How long do sheep live? for the details.

Common sheep breeds

There are more than 200 widely recognized sheep breeds, and the FAO lists well over 1,000 breeds and local types. Some notable ones in Europe and North America are:

• Merino: the world’s leading fine-wool sheep, originally from Spain.
• Suffolk: a large, black-faced English meat breed, widely used in Britain and North America.
• Texel: a heavily muscled meat breed from the Dutch island of Texel.
• Herdwick: a hardy, gray-fleeced hill sheep of the Lake District.
• Soay: a small, brown, primitive sheep from the St Kilda islands of Scotland that sheds its fleece.
• Jacob: a spotted, often multi-horned breed.
• Katahdin and Dorper: hair sheep that need no shearing.

Many traditional breeds now have small populations. In Britain the Rare Breeds Survival Trust monitors native breeds, and in the US the Livestock Conservancy tracks heritage breeds at risk.

Predators and threats

As prey animals, sheep are vulnerable to predators, especially at lambing time. Worldwide, canids, including domestic dogs, are responsible for most predator kills. Coyotes are the main predator in much of North America, while wolves, bears, foxes and large eagles take some sheep or lambs elsewhere. Farmers protect flocks with fences, night pens and livestock guardian dogs, donkeys or llamas.

Sheep and people

Sheep provide wool, meat (lamb and mutton), milk, and leather. Sheep’s milk is the basis of famous cheeses such as Roquefort, feta and pecorino. Sheep are also used in conservation grazing to keep grassland and heath open for wildflowers and insects.

Sheep shaped whole landscapes and economies. Medieval England grew rich on the wool trade, and the Lord Speaker in the House of Lords still sits on the Woolsack, a cushion stuffed with wool, as a reminder. In the nineteenth century Australia and New Zealand built huge wool industries, and New Zealand once had more than 20 sheep for every person. Wool prices have fallen since, so many farmers now earn more from lamb than from fleeces.

A common myth is that sheep are simply stupid followers. Flocking is in fact a sensible survival strategy for a prey animal, and research on memory, learning and emotion shows that sheep are capable animals.

Sheep have a long cultural history, from the Golden Fleece of Greek myth to the many references to shepherds and lambs in the Bible. In 1996, a Finn-Dorset ewe named Dolly, born at the Roslin Institute in Scotland, became the first mammal cloned from an adult cell. For the sheep’s close relative, see the goat.