Nussey D.H., Watt K., Pilkington J.G., Zamoyska R. & McNeilly T.N.

This suggests that there is considerable variation in exactly when an individual sheep starts to show serious physiological decline, although the genetic and environmental factors responsible for this variation have yet to be identified.

(2009) Ageing in a variable habitat: environmental stress affects senescence in parasite resistance in St Kilda Soay sheep. Understanding the reasons why individuals differ in when and how they senesce is an increasingly important challenge in modern biology, as human populations age and we seek to slow or alleviate the physiological declines that typically accompany old age. Close bars and symbols are for all males, while open bars and symbols are for those males that had died at the time of analysis (i.e. Work by Adam Hayward and others has shown that the rate of increase in parasite level with age was exacerbated if females had experienced poorer environmental conditions earlier in their lives (Hayward et al. Aging Cell, 11, 178-180. The Soay sheep is a breed of domestic sheep from Scotland. Current Biology, 17, 2136-2142. The individually-monitored Soay sheep on St Kilda provide an excellent opportunity to study genetics and evolution. 2. Journal of Animal Ecology, 61, 381-396.

(2000). Figure 3. The island of Soay is about 65 kilometers from the Western Isles of Scotland. They are also more susceptible to copper toxicity when mineral supplements are used. Infection, immunity, and demography are rarely measured simultaneously, despite being intertwined.

& Kruuk, L.E.B. Just how high is apparent when considering the paternity of twins: around 75% of twins actually have a different genetic father! The application of capture-mark-recapture models has demonstrated declines in the survival probability after 6 years of age in both males and females (Cathchpole et al, 2000; see figure below). Catchpole E.A., Morgan B.J.T., Coulson T.N., Freeman S.N.

Lifetime breeding success of all study area males born between 1986 and 1996. Soay Sheep (Ovis aries) Origin-Soay sheep are a primitive breed which descends from feral sheep on the 100 hect-acre island of Soay, part of the St. Kilda archipelago.St. It is important to note that the proportion of females in the Village Bay study area the senescent age bracket (7 years old or more) is actually quite substantial.

The net effect, for females at least, is a progressive decline in annual fitness from around 6 years of age onwards, as illustrated in the figure below (from Wilson et al. Relatives share genes – therefore if a particular characteristic or trait such as body size or fertility is strongly determined by genetic effects, relatives should have similar values for that trait and the heritability of that trait is greater than zero. Figure 5. First, and as expected from such systems, male mating success is very uneven, with many rams having low lifetime breeding success and few having high breeding success (Figure 2; Coltman et al 1999). A plot showing that the Soay sheep horn polymorphism, and much of the quantitative variation in normal-horned males as well, is determined by a gene located on chromosome 10. A recent example is our analysis of why the genetic variant (allele) causing scurred or polled horns persists in the population, considering that a male with small horns seems unable to mate many oestrous ewes. A major component of our work on St Kilda is to try and understand the extent to which selection (acting via population crashes or variation in breeding success) on inherited traits results in change (or lack of it) over time. (a) horn type in all sheep; (b) horn type in males only (c) horn length in normal-horned males; (d) horn base circumference in normal-horned males. Less than 1.5hrs from Dublin, we are conveniently close to Waterford, Kilkenny, Carlow and Wexford. The Soay sheep pedigree is a starting point for studies of the mating system and variation in breeding success, the genetic basis of trait variation and understanding microevolution in the population.. 1) The Soay sheep pedigree & Kruuk, L.E.B. Bottom: Proportion of female population in different age classes; Top right, Survival probability as a function of age (from Catchpole et al. They used a library of 2000 blood samples from 800 known individuals that have been left … & Albon S.D.

Studies of female reproductive performance have found declines in the birth weight of lambs and their probability of surviving their first winter as females grow old (Clutton-Brock et al. The Soay sheep population on St Kilda has incredible potential to unlock the reasons for variation in lifespan and senescence patterns in mammals experiencing complex environmental conditions – and we expect more exciting results to emerge soon! References. 2009, 2010).

Maternal effects and early-life performance are associated with parasite resistance across life in free-living Soay sheep.

Parasitology, 137, 1261-1273. Red lines show links to mothers; blue lines to fathers. Mean lifetime breeding success of cohorts of Soay males is determined by density in the year of birth. 2008). During the rut, ewes mate repeatedly during an oestrus lasting between one and four days, and most ewes mate with more than one male; occasionally they are mated by many males. Diet– Herbivore. They feed mostly on grass and are supplemented with hay and meals in the winter. Welcome to the St Kilda Soay Sheep Project. While the heritability of birth weight is very low,, in other studies we have shown that there is appreciable maternal genetic variation for birth weight – i.e., birth weight is partly determined by the genetics of the mother and there is inherited variation for offspring birth weight. They have a two layer wool and the inner fleece is highly developed. This was one of the first studies to show this in a wild vertebrate. their life histories were complete). In principle the higher the heritability, the greater the potential that the trait has to respond to selection on that trait. The attentions of ram lambs contribute to an overall high level of multiple mating by females. Lifespan– 10-12 years, can live for up to 20 years depending on their care. Origin- Soay sheep are a primitive breed which descends from feral sheep on the 100 hect-acre island of Soay, part of the  St. Kilda archipelago. Heterozygous males thus end up with the best of both worlds: high breeding success and long life (Figure 6c). Description- They are most commonly brown or tan with a white belly, white rump patch and/or white markings under the chin. Factors influencing Soay sheep survival. The 1986 and 1989 cohorts were born just after population crashes, while the 1988 and 1991 cohorts were born just before crashes. Ecology, 92, 1936-1947.