Soay sheep are a primitive breed of domestic sheep (Ovis aries) descended from a population of feral sheep on the 250-acre (1.0 km2) island of Soay in the St. Kilda Archipelago, about 65 km from the Western Isles of Scotland. Undiluted by interbreeding, they are a genetic archive of the Neolithic origins of domesticated sheep, and they are one of the Northern European short-tailed sheep breeds. The name "St Kilda sheep" does not refer to the Soay, but is a former name for another short-tailed type, the Hebridean. This breed was raised primarily for meat.[1]
They are similar to the wild ancestors of domestic sheep, the Mediterranean mouflon and the horned urial sheep of Central Asia. Their more immediate origins are uncertain, it being unclear whether they came to the island some time during the Bronze Age, or were brought by Vikings in the ninth and tenth centuries.[2] The name of the island, Soay, is Old Norse, meaning "Island of Sheep". They are much smaller than modern domesticated sheep but hardier. They are extraordinarily agile, and tend to take refuge amongst the cliffs when frightened. The colours tend to be either blonde or dark brown with buffish white underbelly and rump (known as lachdann in Scottish Gaelic, which is cognate to the Manx loaghtan), or totally black or fawn-coloured, a few have white markings. [3] In the early twentieth century, some Soay sheep were translocated to establish exotic flocks, such as the flock of "Park Soay" at Woburn Abbey, established by the Duke of Bedford in 1910, and selected for "primitive" characteristics.[4] A number of Soay sheep were translocated from Soay to the island of Hirta by the Marquess of Bute in the 1930s, after the human population was evacuated.
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Scientific study
The Hirta population is unmanaged and has been the subject of scientific study since the 1950s. The population make an ideal model subject for scientists researching evolution, population dynamics and demography because the population is unmanaged, closed (no emigration or immigration) and has no significant competitors or predators.
The sheep exhibit a phenomenon known as overcompensatory density dependence, in which their population never reaches equilibrium.[5] The population growth is so great as to exceeded the carrying capacity of the island, which eventually causes a dramatic population crash, and then the cycle repeats. For example, in 1989, the population fell by two-thirds within 12 weeks.[6]
The age and sex structure of the population are important in determining when a crash happens; for instance, adult males enter winter in a poor condition after the autumn rut, whereas females have been grazing all summer and so enter winter in a good condition. Survival rates of males (and lambs) are influenced by weather throughout winter (dependent on the strength of the North Atlantic Oscillation), whereas survival rates of females (and adolescents) are influenced most strongly by rainfall at the end of winter, when they will normally be heavily pregnant (the rain soaks the wool, increasing energy expenditure).[5]
Another factor in mortality rates is the loading of intestinal nematode parasites, particularly damaging in malnourished hosts.[6]
Breed characteristics
The sheep have short tails and naturally shed their wool, which can be hand plucked (called rooing) in the spring and early summer. Ewes are polled, scurred or horned and rams are either horned or scurred. They are most commonly brown or tan with a white belly, white rump patch and/or white patch under the chin (referred to as the Mouflon or wild pattern). Occasionally white markings on the face and/or body and legs occur. Rarely self-colored (solid color with no markings) black or tan individuals are seen.
This breed has extremely fine fleece and, in contrast to mouflon, the inner fleece is highly developed and it is difficult to distinguish an outer coat. This is a clear indication that the Soay are indeed the product of a domesticated breed in prehistoric times. The breed also lacks the flocking instinct of many breeds. Attempts to work them using sheep dogs result in a scattering of the group.[7]
See also
References
- ^ "Soay/United Kingdom". Breed Data Sheet. Domestic Animal Diversity Information System. http://dad.fao.org/. Retrieved 2009-09-08.
- ^ "Sheep reveal 'body clock' clues". BBC News. 23 April 2007. http://news.bbc.co.uk/2/hi/uk_news/scotland/highlands_and_islands/6583135.stm. Retrieved 2009-05-04.
- ^ St Kilda Summer, by Kenneth Williamson and J Morton Boyd,Hutchinson and co. Ltd 1960
- ^ Kathie Miller. "History of Soay sheep". Southern Oregon Soay Farms. http://www.soayfarms.com/history.html. Retrieved 2009-05-04.
- ^ a b Coulson, T; et al. (2001). "Age, Sex, Density, Winter Weather, and Population Crashes in Soay Sheep". Science 292 (5521): 1528–1531. doi:. http://www.sciencemag.org/cgi/content/abstract/292/5521/1528. Retrieved 2009-01-13.
- ^ a b Gulland, F. M. D. (1992). "The role of nematode parasites in Soay sheep (Ovis aries L.) mortality during a population crash.". Parasitology 105 (3): 493–503. http://www.ncbi.nlm.nih.gov/pubmed/1461688. Retrieved 2009-01-13.
- ^ "Soay". Breeds of Livestock. Oklahoma State University, Dept. of Animal Science. http://www.ansi.okstate.edu/breeds/sheep/soay/. Retrieved 2009-05-04.
External links
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Wikimedia Commons has media related to: Soay sheep |
- Study discovers secret of Scottish sheep evolution
- Soay Sheep Society of the UK
- (North American) Soay Sheep Breeders Cooperative
- Open Flock Book Project- USA Soay Sheep Database
- Soays of America
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