too many black sheep in the family

Scientists have discovered milder winters are turning the dark coats of Soay sheep on Hirta in the St Kilda archipelago lighter. Dr Maloney, of the University of Western Australia, said: “Our finding that the proportion of dark-coloured Soay sheep decreased over the past 20 years as ambient temperature increased could be interpreted in several ways, the most parsimonious being that dark colouration has provided an energetic advantage in winter that is being attenuated in a warming climate.
The Telegraph, 22/7/09