Survival of the smallest

Humans have evolutionary impact on animals; our prey is getting smaller, breeding earlier

by Rachel Mendleson on Tuesday, February 2, 2010 2:31pm - 7 Comments

(Kraig Lieb/Getty)

As a general rule, it’s tough to get the public engaged in science. Which is why Victoria-based environmental researcher Chris Darimont says he’s “thrilled” about the attention his findings on the evolutionary impacts of hunting and fishing have garnered. His paper, which shows how the targeting of large animals has prompted species to get smaller and breed earlier, was just named one of Discover Magazine’s Top 100 Science Stories of 2009. “I know that it’s infiltrating the world of managers,” says Darimont. “And that, for a conservation scientist, is really important.”

In a sense, his findings were always destined for the mainstream. According to Darimont, a postdoctoral fellow at the University of California, Santa Cruz, and research scientist with the Raincoast Conservation Society, the study gives credence to oft-told anecdotes about how, in generations past, animals were much larger. Based on the meta-analysis of 34 studies, Darimont found that humans have caused swift evolutionary change in species ranging from big horn sheep to Atlantic cod. On average, he says, in the past three decades, body mass has decreased by 20 per cent and reproductive age by 25 per cent.

Though we tend to think of our role in the ecosystem in more civilized terms, in reality, says Darimont, we are predators, “and every predator can have an evolutionary impact on its prey.” Unlike other predators, who typically target the “newly born or nearly dead,” says Darimont, humans go after “large, reproductive-aged adults.” At the same time, regulations often require animals under a certain size be spared, which, says Darimont, “promotes these evolutionary changes.”

With the exception of emails from “a few angry trophy hunters,” Darimont says the feedback he’s received has been overwhelmingly positive. His hope, he says, is that the findings influence policymakers—and us—to rethink how fish and animals are hunted. “It’s not good enough just to do good science,” he says. “It’s got to be injected into the real world, so that changes can be made.”

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  • http://mahout.wordpress.com Andrew Turner

    I doubt it, and I'd like to find out where he got the info for his hockey stick. Hunting has decreased dramatically over the past three decades, and populations have increased hugely, to the point where I think there are more white-tailed deer, mule deer, and ducks (for instance) then there have been in generations.

    This scientist's posit is hokey. I hunt and have for years, and nothing's been shrinking. Size is largely dependent on the protein amount in the animal's feed, and that's about it. Enough of these scientists who lie to make a buck, create massive policy shifts, and then get found out phony.

    • pogomutt

      I'm with you. Sounds like one more publish-or-perish academic pulling a (20% undersize) rabbit out of his hat. I've seen no reduction in size of game animals in my 60 years on this planet. As you say, size may vary a little year-to-year depending on food supply, but an overall species-wide mass reduction of 20%! That's ridiculous. I can't believe MacCleans is giving this story time of day.

      • Ess

        With all due respect to both of you, you are not paid to study these things nor do you have the educational background to do so. This guy does this for a living. I'm pretty certain you don't respond well to "outsiders" critizing your profession. It's called respect. It personally bothers me in this egomaniacal culture WE have evolved into to see people constantly thinking they know better than the experts.

        I would also point out that it appears others do not share your opinion as anecdotal evidence is supporting this scientist's findings. Also, you've ignored the major contributing factor to the shrinkage of animal populations in the wild as a whole: human encroachment on territories.

        • http://intensedebate.com/profiles/shoreboy Andrew Turner

          The whole premise of science is prove/disprove; science not being open to criticism is ridiculous. With regards to my living, as an adult I'm a branding and marketing specialist, and I get a lot of criticism. As a kid, I hunted coyotes for fur, and I'm sure some would criticize that also. That's fine.

          But drawing from this scientist's position, one would arrive at the conclusion that in 150 years (five x thirty) the animals will be so minute as to not exist. An animal cannot reduce in size indefinitely, not unless you expect me to believe that we're going to have deer the size of mice. Likewise with reproductive age: the math doesn't line up.

          Whether this guy knows his job or not, to me this is the equivalent of checking the weather on the computer vs looking out the window: if the computer says it's raining when it's sunny outside, I'd be a fool to think that it is raining, merely because the computer told me so.

  • delford t louis

    the mind…. can make you or break you

  • http://intensedebate.com/people/marvist marvist

    This may be true over the last million years but has nothing to do with humans. We are living in an ICE AGE and if you get to big you can't get out of the way of the ice sheets or follow them back fast enough if you get too accustomed to them. Climate Change has been hell on an evolutionary time scale during the Pleistocene. Human, however flourished killed off the cousins and remade the world. Small with a cerebellum and opposing thumb … can't beat it.

  • http://www.nygoldcashers.com New York Gold Buyers

    Great article Rachel. Hopefully people would do something about this before it's too late.

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