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Does sport hunting affect how animals evolve?

Brief by Central Staff

Wildlife – June 2004 – Colorado Central Magazine

A group of researchers, most of them with Canadian affiliations, have concluded that it does — and the result is to produce animals less desirable to hunters.

They studied the Colorado state animal, the Bighorn Sheep, in the Alberta province of Canada, and examined data going back to 1971.

It turned out that bighorn males are getting smaller — they weigh less, and their horns don’t grow as large as formerly.

Trophy hunters want bighorns with, well, big horns, and that trait is usually accompanied by a husky body.

The researchers theorize that hunters remove the bigger males, usually by age four. Without hunting, the bigger males are better breeders, because they’re better fighters, and thus can keep other males away from their harems of ewes.

But if hunters take them out of the picture, then the smaller males can breed. The offspring are smaller, and the average size of rams and their horns declines.

Or, as the study concludes, “Unrestricted harvesting of trophy rams has thus contributed to a decline in the very traits that determine trophy quality. Hunters have selectively targeted rams of high genetic quality before their reproductive peak, depleting the genes that confer rapid early body and horn growth.”

Is there a solution? They point to one area in Alberta where hunting was restricted to “full-curl” horns, which come after seven or eight years. That gives big-horned rams time to breed and pass on their trophy traits.