Warming temperatures slow lizard behaviors
March 30, 2015
Spring is here, and for most lizards the warming temperatures are a cue to wake up and get busy. However, as global temperatures inch upward, some lizards may end up spending more of their time in the shade cooling off and less time eating and mating. Now, a new detailed physiological and field study of the Puerto Rican crested anole, Anolis cristatellus, shows that lizards are active over a broader range of temperatures than scientists suspected.
“We are not saying that climate change is not a problem for lizards. It is a major problem. However, our study indicates that lizards’ activity levels are less constrained by temperature than previously thought,” said University of Missouri biologist Manuel Leal, who co-authored the study.
Like other cold-blooded animals, lizards have an optimal body temperature at which they hunt, eat, move quickly, and reproduce. For the Puerto Rican crested anole that active range is between 81 and 84 degrees Fahrenheit (27-29 degrees Celsius). Scientists currently project that the lizards would no longer be active at hotter or cooler temperatures.
To test this hypothesis, Leal and Alex Gunderson, his former graduate student who is now a postdoctoral fellow at the University of California-Berkeley, conducted behavioral observations and collected temperature data on hundreds of A. cristatellus within their native tropical habitat on the island of Puerto Rico. They recorded everything the lizards did over fifteen-minute intervals and estimated the lizard’s body temperature.
When they crunched and plotted their data, the researchers found that lizards were most active between 27 and 29 degrees Celsius; however, above and below that temperature, the lizards were hardly inactive.
“They just dialed down the intensity of their activity,” said Leal.
They also found that activity was more sensitive to temperature change than physiological performance (measured as sprint speed), which is often used as a proxy of how warming will impact lizard populations.
Leal said the findings suggest that scientists need to rethink how to model activity in the present and as the climate changes.
“Instead of treating activity as an ON-OFF switch,” says Leal, “we need to start thinking about activity as more like a dimmer switch, where behaviors are being dialed up and dialed down.”
As for lizards, the study finds that global warming is likely to significantly affect their activity levels and that certain aspects of their behavior, including eating and mating, are likely to be more severely affected than physiological performance.
The study, titled “Patterns of Thermal Constraint on Ectotherm Activity,” appeared in the March 11 online issue of the journal American Naturalist.
Written by: Melody Kroll
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