A rare cold snap in Florida has left thousands of iguanas “frozen” and motionless, with some falling from trees. The state’s wildlife agency says the time is ripe to capture them.

Reptiles like iguanas are ectotherms, meaning their internal body temperature is affected by the weather outside. When it gets too cold — temperatures in Florida have dropped below 50 degrees Fahrenheit (10 degrees Celsius) — their internal processes slow down, causing a phenomenon called “cold stunning.”

Florida wildlife agencies are asking the public to capture these iguanas, an invasive species that is not native to the state, when they are motionless. They report that more than 2,000 cold-stunned iguanas have been turned over to authorities so far.