National Geographic News
A photo of a salamander in North Carolina.

Salamanders in the Appalachians, like this Yonahlossee salamander in North Carolina, are getting smaller, says a new study.


Puneet Kollipara

for National Geographic

Published March 27, 2014

The warmer conditions brought on by climate change may cause some animals to change in size, a new study suggests. Wild salamanders in a warming, drying area of the United States have gotten shorter over the past 50-plus years, researchers report this week in Global Change Biology.

The work raises interesting questions about the potential role of climate change on animals, says Joseph Milanovich, an ecologist at Loyola University Chicago, who wasn't involved in the study. Not much research has sought to address how climate change might affect animal size. "This research has really the inherent value of pushing that [area of work] forward," he says.

The research didn't actually start out as a climate change-related project. Karen Lips of the University of Maryland, College Park, said she and colleagues were trying to figure out why salamander populations have been declining in recent decades.

Between summer 2011 and spring 2012, Lips and colleagues caught salamanders of a wide variety of species from nearly 80 sites in the Appalachian Mountains. The researchers sought to assess whether environmental factors, namely disease, might be reducing salamanders' numbers. To their surprise, disease wasn't the problem.

But then they wondered: Maybe climate change was the culprit? They hadn't tested that idea.

"We thought, 'What could we measure that could tell us whether that's even a possibility?'" Lips recalls.

Warmer, Drier Conditions

Scientists had suspected that wildlife might change in size to better cope with the warmer, and perhaps drier, conditions that climate change is bringing on. So the researchers decided to compare the lengths of the specimens they collected with those of museum specimens collected from the same areas from 1957 onward. In total, the analysis included more than 9,000 specimens from more than a dozen species.

From the 1950s to 2012, salamanders from six species got smaller, while creatures from just one species got a little bit larger, the researchers found. On average, salamanders collected after 1980 were eight percent smaller than those collected before then, and each generation of salamander shrunk by one percent.

Moreover, the shrinking effect was greatest in salamanders from the southernmost sites, where temperatures rose the most and rainfall decreased more than in other areas. "I was surprised ... The fact that we're finding some interesting results in a completely unexpected area was pretty cool," Lips says.

Lips and colleagues don't yet know what biological processes caused the salamanders to shrink. Maybe bigger salamanders died or were less likely to reproduce than smaller ones were.

Or the changes could have resulted from "plasticity"—an organism's ability to adjust its biological features, much like an internal thermostat, in response to changes in its environment. The researchers wonder whether warmer or drier conditions might have altered gene activity or other biological processes to stunt the salamanders' growth. What climate change ultimately means for these salamanders is also unclear.

Based on computer models one of Lips' colleagues created, the researchers think that today's salamanders may have to burn more energy in the present-day warmer, drier conditions to stay just as active as their predecessors. That presents trade-offs; modern salamanders may devote more time to finding food and hiding in the shade, making them more vulnerable to predation and giving them less time for mating.

Tackling Unresolved Questions

Lips says she and colleagues are also planning field tests and laboratory experiments to answer the unresolved questions. Laboratory experiments she and colleagues have planned involve putting salamanders in giant incubators and simulating past, present, and future climatic conditions.

"We also need to figure out the relationship between declining populations and body size, to see if they're related or two separate issues," she says.

Milanovich praises the researchers for a highly novel study involving so much data. "I think the framework of their study can and should be replicated, built upon," Milanovich says. Still, he's not totally convinced by the findings.

The researchers, he notes, did most of their sampling in the daytime. Salamanders often come out at night, and stay idle or hidden at daytime to avoid the heat; bigger salamanders may outcompete smaller ones at night, so he wonders whether smaller ones might emerge more at daytime to avoid the competition. If so, the size reduction the researchers reported might be bigger than it actually is.

Lips responds that this may not be such a problem; even when analyzing only the museum specimens, the researchers observe a similar trend—the salamanders' average length decreased.

Follow Puneet Kollipara on Twitter.

Ken Ricklin
Ken Ricklin

I see a pattern with most responses to articles like this that have even a remote connection to AGW.  If one does not agree with the study and has no credible evidence to support a contrary position, he/she resorts to juvenile remarks, conspiracy theories and accusations of greed to distract from the conclusions presented.

I think that at this point one either believes in human-induced climate change and the possible/likely impacts or not.  Personally I find the evidence of this phenomenon to be simply overwhelming and undeniable: "Warming of the climate system is unequivocal", and "Human influence on the climate system is clear".  The following are taken from Headline Statements form the Summary for Policymankers released by the IPCC in January:

Observed Changes in the Climate System

    •    Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.

    •    Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. In the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1400 years (medium confidence).
    •    Ocean warming dominates the increase in energy stored in the climate system, accounting for more than 90% of the energy accumulated between 1971 and 2010 (high confidence). It is virtually certain that the upper ocean (0–700 m) warmed from 1971 to 2010, and it likely warmed between the 1870s and 1971.
    •    Over the last two decades, the Greenland and Antarctic ice sheets have been losing mass, glaciers have continued to shrink almost worldwide, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent (high confidence).
    •    The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia (high confidence). Over the period 1901 to 2010, global mean sea level rose by 0.19 [0.17 to 0.21] m.
    •    The atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. Carbon dioxide concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification.
Drivers of Climate Change

    •    Human influence on the climate system is clear. This is evident from the increasing greenhouse gas concentrations in the atmosphere, positive radiative forcing, observed warming, and understanding of the climate system.
    •    Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes. This evidence for human influence has grown since AR4. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.
These statements are very serious.  So my question to those who do not believe in human-induced climate change is, what will it take to convince you otherwise?  

Paul M.
Paul M.

Earth Hour is about a Climate blame "crisis". The end is near? Who's the neocon?

How "progressive" is it to issue CO2 death threats to your own children just to make sure they turn the lights out more often? Did Bush goose step billions of innocent children to the greenhouse gas ovens of an exaggerated climate crisis so they stay environmentally aware? 

Science has never been certain the END IS NEAR so don't tell our kids that science "believes" as much as you remaining "believers" do.

E Meredith
E Meredith

This finding seems completely rational to me considering that most species get larger if they live in colder climates than the rest of their kin. For example, as western US coyotes spread up into Canada they produced larger offspring than in the previous American southwest. As a result eastern coyotes, relative newcomers who emigrated down from Canada instead of coming east through heavily populated areas, are larger than their ancestors or their native cousins. Seems rational that the reverse happens when a species finds itself in a warmer climate than before.

Don Cuillo
Don Cuillo

Hey guys, that's so scary:  climate change makes the lizard smaller?Really??When it gets really cold it makes parts of me smaller too…Think it could be that polar vortex?Oh, right… that was another grant.Anyway, I’m heavily invested in carbon credits, so could we please keep the subject on “warming” as in “Global Warming..”Trying to make a profit here…Freezing cold doesn’t sell. Frozen over Great Lakes doesn’t sell.Coldest states in decades doesn’t sell guys!Warming, now that’s hot.Push that.Come on now:Group Think:WARMING, WARMING, WARMING!!!

Donny Cuillo

Gerard Van der Leun
Gerard Van der Leun

"The research didn't actually start out as a climate change-related project."  And then the money ran out and they needed a fat grant.... 

Gerard Van der Leun
Gerard Van der Leun

Salamander shrinking! Good gawd amighty, Puneet, is there ANYTHING global warming cannot do?  What a power. No wonder you worship it on your knees.

Paul M.
Paul M.

News editors never mention that the scientific consensus is "could be" and "95%" unlike how the scientists say comet hits are "inevitable" but not their own comet hit of a climate crisis from Human CO2? Believe all you like but do not tell our children that science "believes" as much as you "believers" do.

Scott Pyle
Scott Pyle

Only problem with that whole line of thinking is, the planet is now cooling. If we do have so much influence apparently we have fixed the problem.  We need not get into the false temperatures or all of climate-gate that continues to unfold. Your entire hypothesis is mute and pointless because the whole issue has been reversed.   

But, let us assume for a minute that temperatures are still on the increase. (We might as well.  It's as nice a fairy tail as anything else the IPCC has perpetrated and they are your only source.) 

Who cares.  The real truth is.  When future generations come to look back on the alarm over global warming that seized the world towards the end of the 20th century, much will puzzle them as to how such a scare could have arisen. They will wonder why there was such a panic over a 0.4 per cent rise in global temperatures between 1975 and 1998, when similar rises between 1860 and 1880 and 1910 and 1940 had given no cause for concern.  They will also no doubt wonder why this hysteria was continued by a few scientists (I use that term loosely.) into the 2000's after temps had already moderated.  

Rohn Johnson
Rohn Johnson

@Paul M. .... Wow.  Those comments are "out there," pauly. Be afraid. Be very afraid. If you have escaped your institution, please go back.  You need your meds.

C. Dufour
C. Dufour

@E Meredith  yes what you are saying is true but thats when heat retention is the factor. with salamanders (which are cold blooded), Its about being smaller in warmer conditions so they can better retain moisture.

John Patt
John Patt

@Paul M.  Paul, You're a believer. Only you believe that the 3% are correct, not the 97%.

Scott Pyle
Scott Pyle

Exactly what 97% are you referring to?  They number the IPCC which has been found to be made up?  Using their math. 4+4=732.  See the problem.

Rohn Johnson
Rohn Johnson

@Scott Pyle ... Yeah.  I see the problem.  Look in the mirror.  You'll see it too.  Why do you come to a science site?  There is a flat Earth society.  I think you'd be much more comfortable there, Gomer.


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