Bye bye black sheep thanks to climate change

Mark Macaskill

The oldest flock of native sheep in Scotland are changing colour because of global warming, claim scientists.
The Soay sheep of Hirta — which have been found in the Hebridean islands for more than 4,000 years — have succumbed to climate change and are shedding their dark coats, a new study suggests.
The darker-coloured animals used to have a better chance of survival than the smaller sandy-coloured sheep on the island, as their wool helped them absorb the sun’s warmth to maintain their body heat in harsh Hebridean winters.
However, as temperatures have risen, the sandy-coloured Soays are gaining the upper hand because they need less food to survive and have stronger reproductive genes.
Scientists in Western Australia and South Africa found the proportion of sheep with dark fleeces fell by nine percentage points between 1985 and 2005 as average temperatures rose by about 1C. The findings, published in Biology Letters, a Royal Society journal, suggest sheep with dark coats could disappear altogether. “We suggest that while in the past a dark coat has offset the metabolic costs of thermo-regulation by absorbing solar radiation, the selective advantage of a dark coat may be waning as the climate warms in the North Atlantic,” the study states.
“If environmental effects are the cause of the decline, then we can expect the proportion of dark-coloured Soay sheep to decrease further.”
Scientists from the University of Western Australia and the University of the Witwatersrand in Johannesburg, South Africa, compared Met Office temperatures at Stornoway airport on Lewis, about 50 miles east of the St Kilda archipelago, with population statistics for dark Soay sheep.
They found that the proportion of dark Soay sheep had fallen from 77% to 68%.
Shane Maloney, lead author of the study, said: “Taking the extrapolation to its logical conclusion, if the climate there keeps warming, the sheep will keep getting lighter.”
Soay sheep are one of the most primitive forms of domestic sheep in the world. Before a flock was moved to Hirta in 1932, they were found only on Soay. They are classified as “vulnerable” on the Rare Breeds Survival Trust watch list.
Jacqui Tucker, chair of the Soay Sheep Society, said the number of dark sheep regularly fluctuated and they were being more closely monitored.