don’t tread on a sheep!

Sheep living on a remote island off the coast of Scotland have been shrinking for 20 years. Now it seems shorter winters caused by climate change are responsible.

Soay sheep are a primitive breed of domestic sheep, which live on the island of Hirta, in the St Kilda archipelago, without human interference. From 1955 onwards, the population has been closely studied.

Over the last 20 years, the average size of the sheep has been getting smaller, but it has been unclear why – particularly as natural selection would tend to drive the development of bigger bodies.

Kaustuv Roy, an evolutionary biologist at the University of California San Diego, who was not involved in the study, is impressed. “Their results are really useful, because they tease apart the different processes. It’s a really nice study,” he says.

New Scientist, 2 Jul 2009