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The Soay Sheep Research Project has been running in its present form from 1985 to the present. The key to the research project is the individual recognition of sheep by tagging (see Meet the Sheep). This allows us to follow individuals from birth, through all breeding attempts to death. Our database currently contains information for more than 8,000 individual sheep that have lived in Village Bay in recent years.
The full-time field assistant for the project visits the island three times per year. On each expedition, the study area population is censused ten times and all parts of the study area are searched for dead sheep. This gives key information on which animals are alive, where they are living, who they are associating with. Also, data is downloaded from our three automatic weather stations in Village Bay. The different objectives of each expedition are described below. All the data is entered, as soon as collected, into a database.
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| Weather station in Village Bay |
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Late winter and spring
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The purpose of this expedition is to monitor winter mortality, to catch new born lambs and to conduct a vegetation survey of the study area. The study area is searched daily and post mortem examinations of any animals found dead are made. Once lambing has begun, all ewes are monitored for parturition on a daily basis, and lambs are caught about one day after birth. Each lamb is tagged, weighed, measured, blood sampled (for genetic analysis) and reunited with its mother. A botanical team assesses the sward height and abundance of different plant species throughout Village Bay. | ||||
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Summer
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The aim of the summer expedition the aim is to catch as many Village Bay sheep as possible. Using netting, we reinforce the Head Dyke which surrounds the village, wait for sheep to move in, and then try to enclose and catch them in netting traps: over two weeks we usually catch between 50 and 70% of the population. Each sheep is carefully measured, weighed, sampled and released. The data gives us information about the state of each individual in terms of condition and parasite burden. A team of botanists also conducts the second vegetation survey for the year. In August, we also conduct a whole island sheep count. This requires a good head for heights! (See picture below left)
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Autumn
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During the autumn or rut expedition, the objective is to monitor the rut, specifically to determine when each ewe is in oestrus. A second priority is to catch, usually by darting, any rams that enter the study area in their search for oestrous ewes: we need a blood sample from them to check if they do indeed father any of the Village Bay lambs.
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There is a great deal of work off the island as well. A major activity is the genotyping of all newly-tagged sheep at a selection of variable genetic markers. Once this ‘DNA profiling’ is done, the genetic data for lambs, mothers and candidate fathers is compared and the true father for each lamb is identified. This allows us to measure the reproductive success of each ram and to construct the pedigree of each sheep, allowing several other downstream analyses.
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Photo Credits: Peter Korsten