Is global warming shrinking goats and sheep?

Over the past few days, there has been much press about “shrinking” goats in the Italian Alps. The coverage was precipitated by a new study from Durham University in the UK (see press release).

Researchers claim that goat size has been decreasing over the past 30 years due to global warming. “They discovered that the declines were strongly linked to the warming climate in the study region, which became 3-4̊C warmer during the 30 years of the study. To date, most studies have found that animals are getting smaller because the changing climate is reducing the availability or nutritional content of their food. However, this study found no evidence that the productivity of Alpine meadows grazed by Chamois had been affected by the warming climate. Instead, the team believes that higher temperatures are affecting how chamois behave.” In other words, the heat is making the goats too lazy to forage as much as they did in the past, therefore they don’t grow as much.

By the way, the researchers didn’t actually measure any goats, but relied on reports from hunters and did a bunch of statistical analysis to justify their conclusion. The study is speculative and lacks compelling physical evidence for cause and effect.

But in another “shrinking” story from the UK researchers posited that global warming caused sheep to eat more. “For nearly a quarter of a century the wild Soay sheep on the windswept Scottish island of Hirta have been getting smaller when evolution should have made them bigger.” “Evolutionary theory suggested that the bigger sheep with the most fat would be the most likely members of the flock to survive until the following spring.” In this case, however, the postulated reason for shrinking sheep was that global warming was extending the length of time forage was available, thereby allowing younger, smaller sheep to survive the winter and reproduce.

These studies invoke “Bergmann’s Rule” to explain why goats and other animals are shrinking with global warming. The “Rule” says essentially that in colder climates animals are larger because larger animals have a lower surface area to volume ratio than smaller animals, so they radiate less body heat per unit of mass, and therefore stay warmer in cold climates. I wonder if African elephants and rhinos know about that rule?

So there you have it folks, with global warming both more food and less food shrinks critters. Could global warming also be shrinking the distinction between cause and effect in the minds of researchers?

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