The secret of the Scottish sheep's shrinkage is now revealed:
http://www.sciencemag.org/cgi/content/abstract/1173668
Turns out the sheeps were only adopting to changing climate conditions.
"In 2007, scientists first reported that the sheep were smaller than they had been in the past. This prompted biologists of Imperial College London and colleagues to analyze body weight data going back 24 years. The researchers confirmed that the Soays had indeed been getting smaller. And, as they report online today in Science, the reason appears to be climate change.
In the past, Hirta's sheep gorged on grass during their first summer, the team notes, piling on the weight in order to make it through the island's typically harsh winters. But over the past quarter-century, Hirta has had unusually short and mild winters. As a result, a Turkish researcher, Arpat Ozgul and colleagues propose, grass has become available for more months of the year, meaning the Soay sheep do not have to bulk up as much. In addition, Hirta's harsh winters used to kill small ewes born to young mothers. But now these small ewes survive--and because of their low birth weight, they never get as big as normal sheep. That drives down the average size of the entire population, the team reports. Further mathematical modeling allowed the researchers to propose that natural selection has played little--if any--role in the shrinkage of the Hirta sheep."
Yay, evolution! Yay, veggie diet!
(photo courtesy of Arpat Ozgul)
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