July 3, 2009

Soay sheep shrinking in climate change

Milder weather brought about by climate change is causing Soay sheep to shrink on an uninhabited British island, scientists said.

On Hirta Island in the St. Kilda archipelago, warmer winters and longer summers mean weaker, smaller Soay lambs are surviving to breed and, in turn, produce smaller offspring, said Tim Coulson, a professor at Imperial College London.

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, Coulson said. Soay sheep are one of the world's oldest breeds. The Hirta Island flock has about 2,000 Soay.

In 24 years of study, the average weight of the Soay sheep fell from 66 pounds to 61 pounds and their average leg length shortened by slightly less than a half inch, Coulson told The Times of London in a story published Friday.

Similar effects have been observed in fish, marine iguanas, large-horned Canadian sheep and North American squirrels, The Daily Telegraph (Britain) reported Friday.

Climate change is overriding what we would expect through natural selection, Coulson said.