As humans hunt, their prey gets smaller

[alan1]

As humans hunt, their prey gets smaller: study | Science | Reuters

As humans hunt, their prey gets smaller: study
Mon Jan 12, 2009 5:05pm EST

WASHINGTON (Reuters) - Hunting and gathering has a profound impact on animals and plants, driving an evolutionary process that makes them become smaller and reproduce earlier, U.S. researchers reported on Monday.

Their study of hunting, fishing and collecting of 29 different species shows that under human pressure, creatures on average become 20 percent smaller and their reproductive age advances by 25 percent.

The human tendency to seek large "trophies" appears to drive evolution much faster than hunting by other predators, which pick off the small and the weak, the researchers report in the Proceedings of the National Academy of Sciences.

"As predators, humans are a dominant evolutionary force," said Chris Darimont of the University of California, Santa Cruz. "It's an ideal recipe for rapid trait change."

Darimont and colleagues calculated the rates of trait change with a metric called the "Darwin," after Charles Darwin, who developed the theory of natural selection to help explain evolution.

They studied changes in the size of fish, limpets, snails, bighorn sheep and caribou, as well as two plants -- the Himalayan snow lotus and American ginseng.

In virtually all cases, human-targeted species got smaller and smaller and started reproducing at younger ages -- making populations more vulnerable.

"Earlier breeders often produce far fewer offspring. If we take so much and reduce their ability to reproduce successfully, we reduce their resilience and ability to recover," Darimont said.

The findings fit in with other studies that suggest many fish are over-harvested.

"The public knows we often harvest far too many fish, but the threat goes above and beyond numbers," Darimont said in a statement. "We're changing the very essence of what remains, sometimes within the span of only two decades. We are the planet's super-predator."

Regulations meant to protect the young may in fact be helping drive this unnatural process, Darimont said.

"Hunters are instructed not to take smaller animals or those with smaller horns. This is counter to patterns of natural predation, and now we're seeing the consequences of this management," he said.

(Reporting by Maggie Fox; Editing by Will Dunham and Eric Walsh)

 

[Missourian]

I wonder why they chose sheep and caribou, snails and limpets instead of more popular hunting targets like deer, turkey, raccoons, and ducks?

 

[dilloduck]

I wonder why they chose sheep and caribou, snails and limpets instead of more popular hunting targets like deer, turkey, racoons, and ducks?

so they could prove their point ?

The last 5 deer I shot were all pretty much the same size

 

[alan1]

I wonder why they chose sheep and caribou, snails and limpets instead of more popular hunting targets like deer, turkey, racoons, and ducks?

And what about the plants,

the Himalayan snow lotus and American ginseng

Why not corn and wheat?

 

[Anguille]

But if that's true about getting smaller, don't all animals who are the prey of other animals get smaller?

 

[alan1]

But if that's true about getting smaller, don't all animals who are the prey of other animals get smaller?

Not domesticated ones.

 

[dilloduck]

But if that's true about getting smaller, don't all animals who are the prey of other animals get smaller?

hmmmmm if a guy gets chased around by a bunch of women that could become a real problem.

 

[alan1]

so they could prove their point ?

The last 5 deer I shot were all pretty much the same size

Even the ones that were 20% smaller?

 

[Procrustes Stretched]

But if that's true about getting smaller, don't all animals who are the prey of other animals get smaller?

the more Christians pray the smaller they get


---

edited for no reason whatsoever: a partial thursby


a full thursby would've been a deletion.

 

[alan1]

the more I think about it the more I get the creeps. the more Christians pray the smaller they get. does prayer cause arrested development and/or stunted growth?

Maybe you should start a thread on that, this one isn't about religion, nor in the religion forum.

 

[random3434]

But the weapons get bigger!

 

[Procrustes Stretched]

Maybe you should start a thread on that, this one isn't about religion, nor in the religion forum.

oh pray tell...did I make an error?

 

[dilloduck]

Even the ones that were 20% smaller?

well the ones that were 20% smaller were 40% larger than before so I think that works out.

 

[alan1]

well the ones that were 20% smaller were 40% larger than before so I think that works out.

Nice.

 

[alan1]

oh pray tell...did I make an error?

I don't pray,
but,
yes.

 

[Procrustes Stretched]

I don't pray,
but,
yes.

I was taking to god a little while ago. does that count as prayer?

 

[alan1]

I was taking to god a little while ago. does that count as prayer?

Yer still on the incorrect thread, jr.

 

[Anguille]

the more Christians pray the smaller they get


---

edited for no reason whatsoever: a partial thursby


a full thursby would've been a deletion.

LOL

LOL

and





LOL!

 

[Bern80]

If we could back to the actual thread title:

The last paragraph is a bit telling and for me brings into question how credible the article is and what they authors really know about hunting.

First hunters are not "instructed" to take the largest animal. No one 'instructs' on which animal to take. No one 'instructs' any other hunter I know what to take either.

The reality is there is only so much wall space. My dad shot and had mounted the largest white tail he's seen to this day some 15 years ago. The largest elk he has shot and had mounted was more than 20 years ago. The largest mule deer I've shot I had mounted last year. The largest white tail my brother has seen was shot and mounted last year. The largest walleye I've ever caught was mounted 6 years ago. My dad's 5 years ago.

The point, you may be asking, is that after you get 'the big one' size after that for most hunters becomes irrelevant. I can say with a high degree certainty that my dad will never shoot a bigger elk, and my brother I can say with 99.9% certainty is never going to shoot a bigger white tail rack wise, and he has 40-50 years of hunting left.

The other thing I question about the study is if the human harvest is really enough of a factor that it correlates to what was observed (I don't deny their obervations). Given the deer hunting year in MN I find it hard to believe that humans are haveiung a huge impact on the animal population much less causing any evolutionary changes. We had a hard enough time competeing with the Timberwolves for deer this year and as far as large animals go, white tail deer are probably the number one hunted animal in the country. Interesting that they chose not to study those.

 

[Abelian Sea]

But if that's true about getting smaller, don't all animals who are the prey of other animals get smaller?

Most predators get the small and weak, because it's easier. If this were to have "evolutionary pressure" on the prey species, it would push them to be larger and stronger, rather than smaller.

The article claims that human predators typically go after the big strong specemines, so that the pressure on the prey species is to become smaller.

I remember my Dad thinking along the same lines. I used to go frogging with him, and if we encountered a particularly large and healthy frog, we'd pass him by in hopes of increasing his influence on the local gene pool.


As for the general veracity of the article, I could believe it for the animals they studied, especially fish. We massively and regularly prey on fish for food, but by and large we don't and haven't tried to steer their evolutionary course (via selective breeding) the way we have with chattel and crops. So you have the preference for bigger prey, with no counterbalancing breeding programs, and done on a sufficient scale to actually have an evolutionary impact.

Maybe. Explanations are suspect - especially when a bias is evident in the explaners, like the "human hunters r teh devil" vibe this article puts out - but the raw data is interesting. They're saying that 29 species are getting smaller and reproducing earlier, which does indicate that some sort of game is afoot.