Why Are Iguanas Falling from Trees in Florida?

American songwriters Arthur Johnston and Johnny Burke penned the standard “Pennies from Heaven” in 1936, and it was first performed by American singer and actor Bing Crosby in the film of the same name later that year. According to the song, “you’ll find your fortune fallin’ all over town,” so “be sure that your umbrella is upside down.” But when you’re visiting Florida during a cold snap, that “fortune” just might be a rain of reptiles.

The falling reptiles of note are iguanas (family Iguanidae), the largest of which can grow to more than 2 meters (6.6 feet) long and weigh up to 6 kg (13.2 pounds). Like most reptiles, iguanas are cold-blooded animals (ectotherms). Their body temperature (and thus their metabolism) is dependent on the temperature of the environment, and as outside temperatures increase during the day and fall after sunset, the efficiency of their metabolism follows suit. In contrast, warm-blooded animals (endotherms), such as birds and mammals (as well as a few other species; see also opah) are not constantly at the mercy of the outside temperatures. Although warm-blooded animals can certainly freeze if conditions are harsh enough, their bodies are designed to keep their body temperatures relatively constant. This is done largely through cellular respiration resulting from the breakdown of the food they consume to produce heat.

With respect to iguanas in Florida, during a cold wave (in which the flow of frigid air plunges south into subtropical parts of North America), temperatures can fall below 7.2 °C (45 °F) across the state. These cold-air outbreaks can drive such a rapid decline in the iguanas’ body temperatures and metabolic activity that they enter into a state of dormancy and appear still and lifeless (see also torpor). In the process, iguanas may lose their grip on the branches where they are resting and fall to the ground. Colloquially, this is called “cold-stunning.” Cold-stunning is a condition that also explains why homebound pet lizards and snakes are sluggish during the winter, particularly if their enclosures are inadequately heated. For cold-stunned iguanas, it could take days to recover after outside temperatures rebound.

Of the more than 35 species of iguanas in the world, none are native to the Sunshine State, and three species—the Mexican spiny-tailed iguana (Ctenosaura pectinata), black spiny-tailed iguana (C. similis), and the green iguana (I. iguana)—are the ones most often seen. Iguanas are invasive species that are known to burrow under sidewalks, rip up and damage landscaping, and eat fruits and vegetables from orchards and residential gardens. Green iguanas, in particular, also pose a threat to the state’s native tree snails, and they have been blamed for increases in cases of Salmonella infection in children.

Now what are Florida residents to do if they spot a cold-stunned iguana? Under normal circumstances, Florida residents cannot possess or transport iguanas without a permit; however, during cold snaps Florida’s wildlife officials sometimes issue temporary rules that allow residents to pick up cold-stunned iguanas and bring them to special collection points. This is to prevent them from dispersing and doing more damage after temperatures warm. Florida’s Fish and Wildlife Conservation Commission is quick to point out that iguanas should be contained in closed sacks during transport, in case they recover quickly in a warm vehicle and become aggressive. During one particular cold episode in January and early February 2026, Florida residents and wildlife officials collected more than 5,100 green iguanas, which were later euthanized humanely.