Tropical Animals May Get a Dangerous Metabolic Jolt From Climate Change

By Jennifer Welsh | October 7, 2010 5:49 pm

lizardWhile the temperature effects of climate change are expected to be less dramatic in the equatorial regions, the cold-blooded tropical animals that live there may be in for a dramatic shock.

A study published this week in Nature focused on these cold-blooded animals–including insects, amphibians, and lizards–whose body temperatures are not constant, but instead rise and fall with the temperature of their environment. The researchers found that these creatures show great increases in their metabolism from slight changes in temperature; the metabolic increases were on the order of twice that of warm-blooded animals.

“The assumption has been that effects on organisms will be biggest in the place where the temperature has changed the most,” [first author Michael] Dillon said. “The underlying assumption is that … no matter where you start, a change means the same thing. But with physiology, that’s rarely the case.” [Scientific American].

This means that though climate change will be more extreme in toward the Earth’s poles, the cold-blooded animals that live near the equator (where changes should be milder) may react more strongly to the changes.

The team found this correlation by looking at readouts from temperature records from 3,000 weather stations around the globe, which collected six readings a day between 1961 and 2009. They ran this temperature information through models to determine how the changes over the last 50 years has affected the metabolism of cold-blooded animals.

“If we just pay attention to temperature patterns, that leads us to think we can ignore the tropics, because temperature change hasn’t been very great there,” [Dillon] said. “But even though the temperature change has not been great, the effect on organisms may be really, really big.” [Scientific American].

The findings suggest that these tropical animals will feel the brunt of increased metabolism brought on by climate changes.

“Large effects of recent climate warming on metabolic rates are predicted for invertebrates, amphibians and reptiles in equatorial West Africa, the Caribbean and Central America, Ecuador, eastern equatorial Brazil and the Persian Gulf region,” the report says. [Montreal Gazette]

While the idea of having a higher metabolism isn’t considered bad for people looking to lose their wealth of stored energy (i.e. fat), the researchers are worried about how it might affect the the future of these species, some of which live in areas where food and water is limited.

Dillon speculates that sped-up ectotherms [cold-blooded animals] in the tropics might become more vulnerable to starvation if resources can’t keep pace, he speculates. “If you’re burning more energy, you need more energy,” Dillon says. Food webs may shift. Soil respiration may increase. Mosquitoes may breed faster. Also, in the tropics, Dillon says, “the potential for big impacts on a global scale is the highest there simply because the biodiversity is the highest.” [Science News]

Related content:
80beats: Extinct Goat Tried out Reptilian, Cold-Blooded Living (It Didn’t Work)
Not Exactly Rocket Science: Giant, fruit-eating monitor lizard discovered in the Philippines
Not Exactly Rocket Science: Climate change squeezes jumbo squid out of oxygen
Discoblog: S.O.S.: Global Warming Will Submerge My Country, President Says
DISCOVER: Molding the Metabolism
DISCOVER: Top 100 Stories of 2009 #97: Tropical Heat Speeds Up Evolution

Image: Flickr/Mr. Usaji

CATEGORIZED UNDER: Environment, Living World
  • Rhacodactylus

    I think I’m missing something, don’t most of these animals have behaviors in place to regulate their bodies thermally (e.g. moving from sun to shade, basking on rocks to heat up), is there a reason to think that this wouldn’t be affective if there were an increase in temperature?

    I am in no way saying global warming is acceptable, just wondering about the specifics of this line of thought, thanks.


  • Zachary

    I am saying global warming is acceptable, because the Earth naturally goes through warming and cooling periods. AGW is the most well-intentioned mistake. The science doesn’t support it, and it sadly takes the focus off the myriad ways we are in fact destroying the environment.

  • Jockaira


    Lizards etc. CAN move from sun to shade to help maintain body temperature but they CANNOT move out of the ambient air temperature which also has a great effect on soil temperature, one of the places they might go to in order to escape sun heat.

    I live in a maritime desert environment, high temps (90-110F), high humidity (75-95 RH), and little relief at night, except during two months of winter in December and January (80 days-70 nights). Every morning about an hour after sunrise, the lizards etc. spend a few minutes in the sun warming up. They disappear for the rest of the day, coming out only to grab a quick snack, and then only for the brief time it takes to grab a bug or munch on a leaf.

    When I water my garden, they enjoy it, at first taking a few laps of water then relaxing in the comparative coolness of the water, sometimes immersing themselves completely in small puddles until the sun starts the water to heat up.

    With higher ambient temps and increased aridity (a positive feed-back loop), many of these creatures will probably become rare if not extinct. Other creatures predating on these species will also find it more difficult to survive…and so it goes.

  • Jennifer Welsh

    @ Rhaco,
    The Science News story actually mentioned that as a caveat. Here is what they said:

    “Dillon cautions that plenty of real ectotherms have some ability to moderate their temperatures through behavior, such as darting under rocks to escape the sun. These measures have limits though, especially for small creatures, and actual biology — not just temperature — needs investigating.” (

    Basically, they need to do more experiments to see if their model is correct in real-life scenarios. Thanks for the explanation @Jockaira!

    Thanks for reading and commenting!

  • Rhacodactylus

    Hmm, interesting, I understand the concern but I guess I agree with the authors in that I would love to see how real creatures deal with the issue. For Jackaira, as I understand it tropical creatures will be dealing with the most subtle changes in climate, so maritime desert climates are . . . less than applicable, but I do take your point and thank you for your response.

    As far as Zachary goes, I need you to watch this, as you clearly aren’t focusing on the basic science.


  • Al

    What type of lizard is that in the picture?


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