Is Climate Change Leading To Super Marmots?

A new study published this week in the journal Nature says yellow-bellied marmots in Colorado are getting bigger in size and population. Climate change may be the reason. Robert Siegel talks to UCLA marmot scientist Dan Blumstein.

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ROBERT SIEGEL, host:

A few days ago on this program, we told you about a possible link between climate change and the boom in poison ivy growth. The plant is growing heartier and spreading faster than ever. Well, little did we know that the same may well be true for yellow-bellied marmots in Colorado. They're second cousins to groundhogs or woodchucks.

According to a new study in the journal Nature, over the past 10 years, not only are the marmots getting bigger, but there are also more of them three times more. And, yes, scientists say that climate change may be to blame.

Dan Blumstein is a co-author of that paper and a professor of ecology and evolutionary biology at UCLA. He has studied marmots the world over and he joins us from his field cabin in Colorado, where he's stationed for the better part of the last decade. Welcome to the program.

Professor DAN BLUMSTEIN: (Ecology and Evolutionary Biology, UCLA): Thanks for having me.

SIEGEL: And before we get to these latest findings, why study marmots?

Prof. BLUMSTEIN: Marmots are a good species to study if you're interested in looking at behavior or you're interested in following populations. And that's because unlike many other mammals, marmots have an address. They live in burrows. So if you know where their burrows are, you know where they live.

SIEGEL: Why have their numbers increased so much?

Prof. BLUMSTEIN: In our valley, and we study a five-kilometer stretch outside Crested Butte, Colorado, it's been getting warmer earlier. The snow's been melting earlier, the marmots have been getting up earlier. And for a hibernating species, the name of the game is gaining weight, getting obese. So if the animals don't have to hibernate as long and burn as much fat, they come out of hibernation better conditioned, they're coming out earlier.

So this has led to an increase in survival for breeding age females. And this has led to more breeding age females over the last decade reproducing. And over the past decade, the population has increased. It's been averaging around a hundred. In the last it's gone up to about 300.

SIEGEL: Both more marmots, but also bigger marmots.

Prof. BLUMSTEIN: Yeah.

SIEGEL: How much bigger are they?

Prof. BLUMSTEIN: They're about a pound bigger on average in August than they were 30 years ago.

SIEGEL: Is there some species that feeds off of marmots and is this good news for them? Or have they been missing? What's happened on that score?

Prof. BLUMSTEIN: Well, when - you know, animals follow the resources. So when populations of things that are food for other things increase, then those things increase. So we've been seeing more coyotes. We've been seeing more foxes. Predation is a major factor driving this population out here.

SIEGEL: It seems remarkable that in such a relatively short period of time you could see such a dramatic change in the marmots, in their size and also in the size of the marmot population. First of all, are you struck by that and, second, what's the long-term forecast for marmots?

Prof. BLUMSTEIN: We are struck by, really, we think hitting a tipping point in this valley. The long-term forecast for marmots, though, the ground will not be, you know, knee deep with marmots. Climate models for this region suggest that there's going to be hotter temperatures and more summer droughts. Summer droughts are pretty bad for yellow-bellied marmots.

SIEGEL: You've been at this for a number of years watching the marmots, is their size sufficiently different that you notice it, that the marmot looks different to you in 2010 than it did in, I don't know, 1985 or whatever?

Prof. BLUMSTEIN: Yes, in some cases. This year it's remarkable. We've had for the first time marmots at basically hibernation size and they don't hibernate till September, October. They're already at hibernation body masses in July.

SIEGEL: Are you worried about this, what it says about marmots and maybe down the road, us?

Prof. BLUMSTEIN: I don't know if I'm worried as much as I'm intrigued by it and I want to continue following the story. Most ecological studies are two or three years, which is how long it takes a student to complete his dissertation research, or her dissertation research. Whereas this study has been going on for 49 years. And it's only through these long-term studies that we can gain important insights into what's happening, what's happened and ultimately identify mechanisms through which we may be able to predict what might happen in the future.

SIEGEL: Professor Blumstein, thank you very much for talking with us.

Prof. BLUMSTEIN: Thank you very much.

SIEGEL: Dan Blumstein is a professor at UCLA. He studies marmots at the Rocky Mountain Biological Laboratory in Colorado.

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