Scotch Sheep Shrinking
Despite the evolutionary advantages of larger offspring, the Soay sheep (Ovis aries) on the Scottish island of Hirta have been shrinking in size over the last 20 years. Wild Soay sheep have been under observation by scientists there since 1985. The authors of the study found that the weight of the average female Soay sheep had decreased about three ounces a year, or about 5 percent over the past quarter-century. Dr. Tim Coulson, the lead author of the study, stated that the reason for the decrease in size was due to climate change. As winters on Hirta shortened over the past 20 years, with fall lasting longer and spring arriving earlier, smaller and weaker lambs were able to survive when in prior years they would have died in the longer winter. These smaller and weaker lambs have passed on those traits to their offspring, leading to the Soay shrinking.
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