Green iguanas (Iguana iguana) are not native to the U.S. but were brought to Florida in the 1960s, where they have, for the most part, flourished—except, that is, when temperatures have dropped below 50 degrees F (10 degrees C). These chilly conditions can cause a cold shock in the lizards. And because the iguanas tend to sleep in trees, getting cold shocked can sometimes cause the animals to fall from the skies in an infamous Florida phenomenon. “These tropical lizards were experiencing conditions that they’ve never experienced in their entire evolutionary history before, tens of millions of years,” says James Stroud, an evolutionary biologist at the Georgia Institute of Technology.But in Florida, colder conditions occur every few years—albeit less often as temperatures rise because of climate change. The experience of the iguanas that have been forced to confront the cold in the state can teach scientists more about how animals respond to new climates more generally, Stroud says.

Scientific American | 2026-01-16T00:00:00-05:00