Consequences of hunting

Posted: Wednesday, October 28, 2009

The thrill of the kill. And the bigger the kill, the greater the thrill. Prizes are awarded and photographs proudly record a huge halibut dwarfing the captor, a monster bear at the feet of a hunter, or a moose with a rack wider than the arm-span of its killer. The potential thrill brings some hunters and fishers to pay enormous sums of money to have a chance at the biggest "something" - a trophy animal.

In some cases, landing the biggest fish or bagging the biggest deer/bear/elephant actually represents a high degree of skill, but often no special skill is involved. Indeed, the skill involved in seeking an animal and taking a good photograph must often exceed that of killing the animal. The biggest fish or deer is not necessarily the tastiest either; I've heard fishers and hunters who actually eat their prey say that smaller ones taste better. In fact, hunters of big prey often have no intention of eating the meat but rather take body parts as trophies. So it is not necessarily taste-craving or the exercising of skill that drives a hunter or fisher in search of big prey. It is often thrill-seeking.

University of Alaska Fairbanks Professor Emeritus R. D. Guthrie has suggested that the appetite for hunting and killing is deeply engrained in the human psyche; he calls it "a thirst for the jubilation of the seek- and-kill experience." Humans-as-killers-of-animals goes back a very long way, several million years, and the excitement of taking big prey may be as old. (This is not to imply that all humans share this joy in the killing experience.)

Very few trophy seekers pause to consider the consequences of their targeted hunts. Yet scientific studies show that reducing the number of large animals in a population can have very serious consequences, some of which ultimately reduce the availability of trophy animals for future hunters or fishers.

Here is one well-documented example: A population of bighorn sheep in Alberta has been studied for more than 30 years. This population is subject to intensive selective hunting of trophy rams; about 40 percent of legal-size rams are killed every year. These are the rams most likely to be dominant over smaller rams with smaller horns, and therefore most likely to be able to mate successfully with ewes, in natural circumstances. Curtailing the lives of these large individuals (which would have high survival rates if not hunted) means that they leave fewer offspring than otherwise expected. And since body size and horn size are, in part, genetically controlled, this means that the genes for large bodies and big horns become ever-fewer in the population. In fact, body size and horn size of rams in this population have declined significantly, decreasing the availability of trophy-quality animals. In short, there has been an evolutionary response to sport hunting in this population, toward smaller and smaller rams, which have been the ones remaining to father the next generations. So, even though one male sheep can fertilize several females, it really matters which males do the job.

Similar effects of selective killing of males, especially dominant males, are reported for many other hunted populations, including fish and invertebrates. There may be other consequences as well, including the entire collapse of the animal's social system and decreased rates of pregnancy (e.g., saiga antelope), increased infanticide (bears, lions) and corresponding habitat shifts of females to avoid infanticidal males (often to lower quality habitat, so reproductive rates decrease), lower frequency of male offspring (moose), increased stress levels, decreased foraging time, lower body condition of females, and increased abortion rates (zebra).

It is well-documented that the evolution of size, behavior, or physiology can be very rapid, with significant changes occurring in just a few generations. But the ecological and evolutionary effects of size-selective harvest of prey animals is seldom considered, in wildlife management plans or conservation projects, despite a solid body of scientific literature on the subject.

One author has proposed that humans have become the "world's greatest evolutionary force." It is past time for the principles of evolution to be incorporated in wildlife management and conservation.

• Mary F. Willson is a retired professor of ecology and a Juneau.

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