What happens to iguanas when cold weather strikes? Florida phenomenon explained

Colder air and a frigid wind chill in South Florida this week are expected to give rise to a phenomenon somewhat unique to that part of the country: falling iguanas.

The invasive reptile − believed to have been introduced to the state in the 1960s as part of the exotic-pet trade − normally thrives in the Florida heat, which matches the iguanas' native range, which extends from Central America to tropical regions of South America and some eastern Caribbean islands.

But when cold fronts move in carrying chilly northern winds, temperatures under 50 degrees can immobilize iguanas in trees, causing them to lose their grip and fall to the ground. Though the condition is temporary, it can make turn paralyzed iguanas into easy prey for bobcats and coyotes.

Why do iguanas become paralyzed in the cold?

Iguanas are cold-blooded reptiles that need external heat sources to regulate their core body temperature. They are active during the day and can be found basking in sunlight on the ground, on rocks and in trees. Where sidewalks and other warm surfaces are present, it's not uncommon to find them basking there.

But according to officials from the Florida Fish and Wildlife Conservation Commission, the state's non-native green iguanas can become immobilized when air temperatures drop to 40 to 50 degrees. Barring an attack by a predator or being run over by vehicles on a roadway, iguanas usually bounce back when the warm weather and sunshine return. However, if iguanas are immobilized for too long during extended cold snaps, their digestive systems can sour and create deadly bacterial infections.

The last major cold-induced die-off of iguanas occurred in January 2010, when West Palm Beach's overnight lows dropped into the 30s nine times in an 11-day stretch.

What do you do if you see a fallen iguana?

Immobilized iguanas appear to be sleeping or dead but will wake up and move normally when temperatures warm. They are wild animals with sharp teeth and claws, so experts recommend leaving them alone.

Contributing: Kimberly Miller, The Palm Beach Post

SOURCES The Palm Beach Post; Naples Daily News; Florida Fish and Wildlife Conservation Commission; University of Florida