Florida's Iguanas Are Adapting to Cold in Real Time

Imagine tropical lizards experiencing temperatures they've never faced in tens of millions of years of evolution. That's exactly what's happening to Florida's green iguanas this week as temperatures plummet into the 30s and 20s Fahrenheit.

These five-foot reptiles aren't native to Florida. They arrived in the 1960s from Central and South American rainforests, where temperatures stay wonderfully consistent. Now they're getting an evolutionary crash course in adaptability.

When temperatures drop below 50 degrees, the iguanas experience cold shock while sleeping in trees. The result is Florida's most surreal weather phenomenon: iguanas raining from the sky. Before you panic, they're usually fine once they warm up.

James Stroud, an evolutionary biologist at Georgia Institute of Technology, sees these falling lizards as a rare opportunity. Scientists don't often get to watch in real time how animals respond to completely new climates.

During a 2020 cold snap, Stroud and his team made a fascinating discovery. The iguanas that survived the chill became more tolerant of cold temperatures afterward. The lizards were literally adapting before researchers' eyes.

The Bright Side

This unexpected natural experiment is teaching scientists crucial lessons about how species respond to rapid climate changes. While the iguanas aren't native and can be considered invasive, their struggle reveals something hopeful about nature's resilience.

Stroud is now working to understand whether this cold tolerance represents true evolution or simple adaptation. Either way, it shows that even when confronted with conditions never experienced in their entire evolutionary history, living creatures can find ways to adjust.

The cold snaps happen every few years in Florida, though less frequently as overall temperatures rise from climate change. Each event creates another learning opportunity for both the iguanas and the scientists studying them.

If you spot a cold-shocked iguana, Stroud has simple advice: leave them alone. Unless they've fallen from high enough to cause injury, they'll wake up once the sun warms the air. No blankets needed.

These tumbling tropical lizards are writing a new chapter in their species' story, one chilly Florida morning at a time.