Opinion - News Analysis

Mystery of Scotland’s shrinking sheep solved

The mysterious shrinking sheep on the island of St Kilda far off the west coast of Scotland, sounds like a job for Sherlock Holmes. A rare herd of wild Soay sheep on the remote island are refusing to bow to conventional evolutionary pressure, which says big is best. Scientists have fingered the culprit as the new Moriarty of mankind: global warming.

The experts say the island’s shorter and milder winters mean that lambs do not need to put on as much weight during their first few months.

Smaller animals that would have perished in harsh winters a few decades ago can survive to their first birthday. As a result, the average weight of the sheep has dropped by 81g each year.

The difference is too small to see with the naked eye, but is important because it shows how animal populations can respond to climate change.

Tim Coulson, a biologist at Imperial College London who worked on the study, said: “If animals can respond fairly rapidly [to climate change], then evolution could play a role in helping them to adapt.” The results appear in the journal Science.

Biologists have reported that several species of birds and fish are changing size and shape, which could be down to global warming. The study looked at a herd that biologists have studied since 1985. Dogs are forbidden on the island - known in Scottish Gaelic as Hirta — so the scientists herded the animals, which are expert jumpers, towards areas where they could be weighed. . — © Guardian Newspapers Limited, 2009

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