What happens to tropical lizards when Florida freezes

South Florida's lizards come mostly from the tropics, and every one of them has a lower limit: a body temperature at which it can no longer turn itself the right way up, known as its critical thermal minimum. On 22 January 2020, air temperatures in Miami fell below the limits of the lizards living there.

We happened to be ready for it. In October and November 2016 we had measured the cold tolerance of six lizard species living together in Miami: four anoles (the green, brown, crested and bark anoles), the brown basilisk and the African house gecko. They differ in size, habitat and physiology, and before the cold snap their cold limits differed too.

Six species, one new limit

In the week after the freeze we measured all six species again. As a community they could now tolerate colder temperatures, and species that had differed beforehand had converged on the same new, lower limit, averaging about 7.2°C. Ten weeks later the new limits were still in place in the five species we could resample (COVID-19 curfews ruled out night sampling for the house gecko).

How does a lizard's cold tolerance change so fast? Two explanations are possible, and they are not mutually exclusive. The cold may have killed the least tolerant individuals, leaving a population shaped by selection, or the survivors may have adjusted their physiology in response to the cold itself. Either way, the result cuts against a common assumption: tropical and subtropical cold-blooded animals are often thought unable to withstand rapid swings in climate, yet these lizards endured conditions beyond their measured physiological limits.

Back out in the cold

Extreme cold events keep coming. When another hit Miami in February 2026, the lab was out at 4am, in winter hats and head torches, ready to sample cold-stunned lizards. A study with colleagues on how lizards lose, and then recover, the ability to move after cold exposure is currently in review. It connects to our research on green anoles further north, where surviving winter is the central challenge for a lizard of tropical origin (see the green anole guide).

The 2020 study, led by James Stroud and Caitlin Mothes, was published in Biology Letters.

In the news

• The Washington Post Florida cold temperatures pose risk to people, crops and iguanas January 2022
• CNN Florida's falling lizards are getting used to cold winter temperatures October 2020
• Scientific American It's so cold in Florida that iguanas might rain from the skies January 2026
• Smithsonian Magazine Lizards Fell From Palm Trees During a Florida Cold Snap, but Now They've Toughened Up 2020
• Science News How frigid lizards falling from trees revealed rising cold tolerance October 2020
• Phys.org What cold lizards in Miami can tell us about climate change resilience October 2020

Read the research

• An extreme cold event leads to community-wide convergence in lower temperature tolerance in a lizard community. Biology Letters (2020)
• Beyond Righting Response: Disentangling cold-induced loss and recovery of motor function in lizards. (2026)