North Ronaldsay sheep
Two sheep on the shoreline of North Ronaldsay
|Country of origin||Scotland|
|Wool color||White, grey, brown, black|
The North Ronaldsay, also known as the Orkney, is a breed of sheep living on North Ronaldsay, the northernmost island of the Orkney Islands, Scotland. They are one of only 2 surviving, descendant breeds of a type of sheep formerly found across the islands of Orkney and Shetland (the other is the Shetland sheep), belonging to the Northern European short-tailed sheep group of breeds. The breed is very close to the original prehistoric North European short tail breed. North Ronaldsays are smaller sheep than most, with the rams (males) horned and ewes (females) typically hornless. This breed is raised primarily for wool.
The semi-feral flock on North Ronaldsay is the original flock that had to evolve to live almost entirely on seaweed, as they are confined to the shoreline by a 1.8 m (6 ft) tall dry-stone wall which encircles the whole island. This was built originally to protect the shoreline and keep the sheep inside the dyke, but as the seaweed farming on the shore became uneconomical the sheep were banished outside to protect the land inside for crops and animals. The flock on North Ronaldsay is the largest flock of the breed currently, with smaller flocks on the island of Linga Holm and mainland Scotland.
They are physically a very small, primitive, sheep breed, which is an adaptation typical of animals in harsh, cold environments. Rams typically weigh around 30 kilogrammes, and ewes rarely exceed 25 kg, and both stand around 41 centimeters high at the withers (shoulders).:873
The North Ronaldsay is a descendant of the primitive European Short Tailed sheep breed. As the name of the descent parent would suggest, they have naturally short tails. Their bones are also finer than other breeds and their head is dished.:873 Rams are all horned, these horns are typically ridged and spiraled. However, only 20 percent of the ewes are horned, the rest are polled (hornless).
The North Ronaldsay sheep are noted for their incredibly unusual diet, almost consisting solely of seaweed. This has evolved due to their unique location, confined to the shoreline by a 1.8 m (6 ft) high dry stone wall, leaving only the seaweed for food. Apart from the Marine Iguana, native to the Galapagos Islands, they are the only known animal to do this. The sheep have been studied for this, and it has been observed that due to preference and availability, they mainly eat brown kelps. This discovery led to suggestions that kelp may be of use as an alternative food source for other livestock.
The grazing habits of the sheep have also adapted to their unusual diet: instead of grazing during the day and ruminating at night as other sheep generally do, (knows as a diurnal feeding pattern) the North Ronaldsays graze as the tide reveals the shore (twice in 24 hours), ruminating (digesting) at high water. Feeding begins around 3.5 hours after high tide, as the areas of kelp and seaweed are exposed. 4 hours later, which is just after the low tide, feeding ends allowing rumination to begin. This cycle reduces the chance of the sheep becoming stranded at sea; with the incoming tide trapping them.:30
Unusually for sheep, the North Ronaldsay fattens in winter. This is due to the winter storms on North Ronaldsay throwing larger amounts of kelp and seaweed onto the shore, causing food to be in abundance.
The sheep's source of fresh water is limited to the few freshwater lakes and ponds along the seashore.:60 This has led to the sheep becoming very salt tolerant, as their diet contains lots of salts and access to fresh water is limited. When compared to other breeds of sheep, they can far better handle elements present in salts, such as sodium.:3 The biological mechanism enabling this is yet to be understood, but these empirical conclusions were drawn in a 1997 study.:30
The sheep have evolved a somewhat different physiology from other sheep, due to their unusual diet – their digestive system has adapted to extract the sugars in seaweeds more efficiently.:97 A 2005 study at the University of Liverpool found that they have an increased susceptibility to toxicity to the trace element copper, when compared to a more traditional breed such as the Cambridge. This is because seaweed has a chemical which inhibits the absorption of copper, so the sheep have to more efficiently absorb copper to obtain the required amount.:97 This results in normal levels of copper, present in more typical foods like grass, being far too great for the sheep's physiology to handle, harming the sheep. Copper is toxic in too great quantities to sheep:873 Studies at the Universities of Liverpool and Minnesota suggest that they can extract four times more copper from their diet than more traditional breeds.
Also, the sheep have been studied to find that they have higher carbon 12 : carbon 13 ratio (δ13C) levels. Radiocarbon dating has showed a δ13C level of −13‰ (13 parts per thousand) which far exceeds that of any breed of grass fed sheep. This is because their diet has a far greater δ13C content than that of grass. This discovery was used in a 2005 study to analyse if some parts of the sheep population did eat grass. δ13C levels present in their seaweed diet are far greater than those on a grass diet. Therefore, swabs were taken from the sheep and analysed for the δ13C ratio. It was concluded that there was variation in the population as some sheep exclusivley fed on seaweed, whereas others consumed a diet consisting of half grass in the summer months.
Due to their unusual diet, the lamb and mutton from the sheep has been specially designated by the UK Government. The unique, rich flavour of the meat, which has been described as "intense and almost gamey", comes from their very iodine rich diet and traditional methods of raising the sheep. Their protected status by the UK Government as 'Orkney Lamb' means that only pure-bred sheep, which have produced pure bred lambs, can be marketed as 'Orkney Lamb'.
Due to their slight size, North Ronaldsay sheep were historically raised for their wool. It comes in a variety of colours, and is very similar to the Shetland breed, due to their common ancestor. More common typical colours are the whites and greys, but browns, beiges, reds (also called tanay) and blacks, where the hair tends to be coarser, are all exhibited.:59 A full fleece will weigh around 1 kg.:873:176
The North Ronaldsay is a double coated breed of sheep, meaning that they have an undercoat and overcoat of wool. The undercoat tends to be more fine and soft, suitable for garments that would touch the skin, whereas the overcoat is more coarse, with long hair that protects the sheep from the cold, wet weather of their natural environment. This fibre is more durable and tends to be used in overgarments.
The sheep descend from the North European Short-tailed. The time of arrival onto North Ronaldsay is not known precisely but it has been said it was as early as the Iron Age. This means that it is potentially the earliest ovine arrival into Britain, and due to its isolated location has evolved without much admixture from other sheep breeds.:872 It has avoided crosses with imported Roman and European breeds of sheep, to Britain at various points.:96 However, the sheep do share some characteristics common with the Scandinavian sheep which were introduced to the islands between the 9th and 15th centuries when the islands were under Norse control. This introduced characteristics such as the colour range present in the flock and the continuation of the short tails trait.
In 1832, a dry stone wall, known as a dyke, was erected to confine the sheep to the inside of the island, protect the seaweed on the shore, that would be harvested for iodine extraction. However, iodine extraction became uneconomical, and the sheep were banished to the outside of the dyke to prevent them from wandering onto fields, or crofts, to make way for more valuable cattle. The dyke also unintentially reduced the chances of cross-breeding, which would damage the gene pool of an already vulnerable breed. This keeps the north Ronaldsay 'pure-bred'. This dyke circles the whole of the coast of the island (19.2km), and is 1.8 meters (6 ft) high, which makes it the largest single drystone entity in the world. It is an 'A' listed structure by Historic Scotland. It was designated this status in 1999 in order to protect and conserve "the unique and important structure". This status affords the structure special protection from development in order to preserve the original structure; any development has to be specially approved with conservation in mind.
Since the dyke was erected, the population of North Ronaldsay has fallen from 500 to around 50. This large fall in the population of the island has meant that the current islanders lack the skills to maintain the dyke. Successive storms, the worst of which was in December 2012, have created large holes in the structure and the cost of repairs was estimated at £3 million. In 1902, it was estimated that it cost 4d (4 pence) per hour to repair the wall but currently this has skyrocketed, in part due to the lack of natural material and skilled labour. The stone for the wall used to be taken from the shoreline, but now has to be imported onto the island. Small repairs have been carried, but it was estimated in September 2015 that 4.9km of the 19.2km long wall needs repair and that current damage is outstripping the pace of repair by Historic Scotland.
The punds, or pounds, are 9 small enclosures situated across the island to contain the sheep for shearing, counting, lambing and slaughtering.:210 The sheep are herded inside these punds 2 times per year, and it is the only time they have access to grass feed. However, many still choose to consume seaweed. Between February and August, the sheep are brounght into the punds twice - once for lambing and once for shearing. The lambs are born on the grass between February and May. At this time, the sheep are also counted and lambs are given ear-tags and records entered with the island's sheep court to record ownership.:97:155 Shearing takes place in the summer, betwene July and August and the whole island community is involved in hearding and shearing the sheep.:176
Slaughtering will only take place in winter, when the meat is needed. Also, the animals are fatter, due to their diet during winter so yield more meat at this time.:97
The punds are listed with Historic Scotland, along with the stone dyke.
The North Ronaldsay Sheep Fellowship is the primary organisation concerned with the survival of the breed. They maintain the flock book, established in 1974, which is the breed registry containing all purebred animals. This book reports that there are less than 600 breeding females and less than 3700 sheep in total. The Rare Breeds Survival Trust (RBST) lists the North Ronaldsay as "vulnerable".
There are only 2 main populations of the breed, one on the island of North Ronaldsay itself, and the other was established in 1974. This was when the RBST took 178 sheep off the island and attempted to establish new populations. One group of sheep went to the mainland, and the other went to the uninhabited island of Linga Holm. The RBST purchased this island and sent 150 sheep there. This was to diversify the population's geographic locations to protect from potential natural disasters, such as an oil spill; North Sea oil extraction was expanding.
Modern DNA analysis has shown that there is only a mild introgression with other sheep breeds from mainland Britain. Testing, carried out under the National Scrapie Plan, analysed the frequencies of the ARQ allele. This is an allele associated with resistance to the disease scrapies, and is present in modern selectively bred breeds of sheep, and not associated with the North European Short-tailed group. Therefore, analysis to see if the resistance allele is present in some of the population is analysis to see if there is crossbreeding from other modern breeds of sheep. A low number, (1.3%) of North Ronaldsay sheep were observed with the resistant allele which shows that there is a low amount of cross breeding.:873
Further DNA studies comparing the bones of the North Ronaldsay with the North European Short-tailed remains found on the Skara Brae site which dates from around 3000 BCE, have shown a very close match suggesting that the North Ronaldsay has not genetically mixed with other breeds.
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Media related to North Ronaldsay sheep at Wikimedia Commons