Ananova:

Climate change is causing a breed of wild sheep in Scotland to shrink, according to researchers.

Scientists say milder winters are helping smaller sheep to survive, reports the BBC.

Researchers first began studying Soay sheep, on the island of Hirta in the St Kilda archipelago, in 1985.

Since then, the sheep have decreased in size by 5% - their legs getting steadily shorter and their body weight decreasing.

Lead researcher Tim Coulson, from Imperial College London, said: "The island is almost like a natural laboratory - there are only the sheep and the vegetation there.

"In the past, only the big, healthy sheep and large lambs that had piled on weight in their first summer could survive the harsh winters on Hirta."

But because of climate change, grass for food was now available for more months of the year on the island.

"Survival conditions are not so challenging - even the slower growing sheep have a chance of making it, and this means smaller individuals are becoming increasingly prevalent in the population," he said.

"The next step is to extend our description of past change into a predictive model. But it's too early to say if, in 100 years, we will have chihuahuas herding pocket-sized sheep."