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Study finds trophy hunting leads to smaller animals – science fact or science fiction?

Submitted by andy on Sat, 01/17/2009 - 05:53

A male Key Deer stands at about 55 lbs.
Key Deer live on the Florida keys and
have no natural predator, allowing them
to have such a small stature.

There recently was a post in our forums asking whether you should shoot a spike or pass it up. Latter on
I came across a news articles about a study that shows trophy hunting may be forcing smaller individuals.

The report was released by the Proceedings of the National Academy of Sciences, and shows those species hunted by man (such as bighorn sheep, caribou, salmon and cod) are forced to evolve at a rapid rate. In fact the article states that the animals have decreased in body size by 20% over 30 years. So what gives.

The idea behind this is that smaller animals are often passed on by hunters, and they are allowed to continue to breed. Larger individuals are taken, and have a smaller opportunity to pass on their genetics. Humans act as a “super predator,” often taking a large portion of the population at one time.

Dr. Tom Reimchen, a professor at the University of Victoria puts it this way: "On average, most predators tend to target the young ones, these are the ones that can't defend themselves, or the old and decrepit .... We come in as a super-predator and target those that are the prime in the population."

I have never been a fan of news articles that only present one side of a story, so I went out and looked for a rebuttal to the story, and I found a very well written one. I would now like to direct you to that
written article by “Black Bear Blogs” located here

In it the author quotes multiple researchers who present interesting rebuttals. One, by VALERIUS GEIST, Professor emeritus, Faculty of Environmental Design, The University of Calgary, Calgary, Alberta, Canada, states that trophy bucks have a tendency to accidentally have their antlers become intertwined and locked. There are stories of hunters coming across two dead deer with their antlers locked. The professor also tells this story:

“During eight years of field work with habituated mule deer in Waterton National Park, Alberta, Canada, I was fortunate to closely observe three bucks with exceptionally large antlers. All three became “shirkers” during the rutting season. They avoided other deer, bucks especially, and thus failed to court and breed females. They merely fed and rested in seclusion. However, one of these bucks had a surprising history. He had been a normal rutting buck up to three years of age. During a fight with an old buck, he was flung upward and landed on his back in some wind-blown aspen trees. He quit rutting that year and for two more years. By then, he had grown to a very large body and antler size. The next rutting season he reversed and became a fully engaged, breeding master-buck. He continued as such for three rutting seasons. Hence, “shirking” is potentially reversible. Nevertheless, managing populations for trophy size remains highly questionable, as do the stated concerns of Coltman et al.”

Also stated in another rebuttal is that this study fails to account for 50% of the gene pool, the females of the species. These individuals are often not highly targeted by hunters.

Are trophy hunters causing animals to shrink or is it just bad science? We invite you to take up the discussion in our forums.

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