Rodent size linked to human population and climate change

July 31, 2009

You probably hadn't noticed -- but the head shape and overall size of rodents has been changing over the past century. A University of Illinois at Chicago ecologist has tied these changes to human population density and climate change.

The finding is reported by Oliver Pergams, UIC research assistant professor of biological sciences, in the July 31 issue of .

Pergams said that such size-and-shape changes in mammals, occurring around the world in less than a century, are quite substantial.

He had done earlier studies on a century's worth of anatomic changes between two geographically isolated rodents -- Channel Island deer mice from coastal California and white-footed mice northwest of Chicago -- and noted fast change among both.

"I suspected they weren't unique examples," he said. "I wondered whether these changes were occurring elsewhere, whether they were global in nature, and what some of the causes may be."

Pergams examined specimen rodents from museums around the world, including the big collections held at Chicago's Field Museum and the Smithsonian in Washington. Altogether, he recorded more than 17,000 body and skull measurements from 1,300 specimens from 22 locations in Africa, the Americas and Asia. The animals were collected from 1892 to 2001, and Pergams compared those from before 1950 to those collected after.

He also compared specimens gathered from sparsely populated islands to those from the mainland, where human populations were denser.

Pergams found both increases and decreases in the 15 anatomic traits he measured, with changes as great as 50 percent over 80 years. Ten of the 15 traits were associated with changes in density, current temperature, or trends in temperature and precipitation.

"Rapid change, contrary to previous opinion, really seems to be happening quite frequently in a number of locations around the world," Pergams said. "There seem to be significant correlations with 'people-caused' parameters, such as population density and anthropologically-caused ."

While Pergams' study was by no means comprehensive, it was the first attempt of its kind to examine data on mammals from many global locations to find links between morphological change and variables such as population density and changing climate.

"Species can adapt quickly to rapid environmental changes -- quicker than many people have thought, especially for mammals," said Pergams. "Those mammals that can adapt quickly have a much higher chance to survive big environmental changes caused by humans. Understanding which species and populations have the greatest ability to change has a crucial impact on being able to conserve biodiversity."

Source: University of Illinois at Chicago (news : web)

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5 / 5 (1) Jul 31, 2009

It sounds like SPAM whenever you post.

3.4 / 5 (5) Jul 31, 2009
Some guy measures city rat sizes, see's a correlation with the amount of garbage available (because that correlates with the amount of food available) , and the headline tells us its about global warming? Congratulations, physorg. You've just earned the title of "Rag". Oh and I'll have one less entry in my list of browser bookmarks, too. Bye all. its been fun.
3.5 / 5 (4) Jul 31, 2009
and the headline tells us its about global warming?

Funny how you see things that aren't there. I suppose you won't see this either.

It says:
Rodent size linked to human population and climate change

Climate change. Not global warming.

For a rat that includes things like CITY INDUCED WARMING. Cities tend to be 10 degrees warmer than the surrounding countryside. Its due to a lot things like

Black top
Lack of trees
buildings blocking wind

We aren't just a food source for rodents. Cities have a better climate in the winter for them.

3.7 / 5 (3) Jul 31, 2009
So now we know. Rats drive global climate change and human populations.
Seems as reasonable as anything I've heard recently.
3 / 5 (2) Aug 01, 2009
You might want to consider getting your hearing checked. You seem to be hearing things that weren't said. At least in this thread.

Besides I heard that it is COWS that are driving global warming by farting. And don't forget sheep. Those miserable furry beasts are not just eating all the grass to kill off the cows they are farting the world to death. They have no brains so they must fart their way to victory. They are tired of those itchy wool coats they wear and warming up the place is their way to fix the wool itchy wool problem.

If you don't understand the terrible danger of farts it is time you read John Scalzi's Android's Dream. There you will find out just how deadly a fart can be. It not necessary to use a fleem to kill. Odorized gasses will do trick quite well if you are a clever and ambitious ruminant.


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