Body Condition and Ranging Behaviour of Blackface Hill Sheep in Relation to Lamb Survival

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Abstract
Factors affecting the production and survival of lambs, including vulnerability to predation, were studied in a flock of about 850 Blackface hill sheep in Argyll, West Scotland. The poorer production of lambs by gimmers (sheep breeding for the 1st time) was not due to a lower pregnancy rate or to poorer body condition, but may have been affected by poorer maternal care. Lambing reached a peak between 4-10 May. Sheep withdrew from the flock to lamb and returned within 1-3 days. If the distance between sheep and their lambs is regarded as a measure of vulnerability to predation, then lambs of ewes were less vulnerable than those of gimmers. Sheep moved uphill at night, but less so in June than in Feb.-March. The numbers of sheep within a circle of 50 m estimated diameter increased between afternoon and evening. The anti-predator value of this behavior is discussed. Home ranges in the lambing period varied from 33-55 ha, with a mean of 44.4 .+-. 1.7 ha. These were larger than in other studies of hill sheep in Scotland.