Unusually cold Florida weather causes cold-stunned iguanas

In early January, Floridians were shocked to see green iguanas (Iguana iguana) falling out of trees or lying on the ground, apparently dead. But the iguanas weren’t dead — they were stunned by the cold.

“At about 40 degrees F, green iguanas may become immobile due to lack of blood flow,” said Sarah Lessard, a spokeswoman for the Florida Fish and Wildlife Conservation Commission Division of Habitat and Species Conservation. And South Florida was experiencing unusually cold weather — between 30 and 40 degrees Fahrenheit  — earlier this month.

The cold snap may not have been long enough to significantly impact the population, Lessard said, but the effects are difficult to quantify.

“We do not have a population estimate for iguanas,” Lessard said, “so, we do not know exactly how many iguanas died, or what proportion of the population was affected.”

Green iguanas are invasive in Florida, and can be a nuisance to homeowners, damaging landscaping, leaving droppings in yards and pools and digging burrows on the landscape.

“Iguanas may impact sensitive natural resources in Florida, but we do not know the extent of that threat,” Lessard said.

This isn’t the first time this has happened. Large iguanas have been known to become sluggish and even fall out of trees around 50 degrees. In January 2010, almost two weeks of cold weather may have killed a portion of the iguana population.

Cold weather can offer the unique opportunity for landowners to control their nuisance iguana populations, Lessard said. Iguanas may be humanely captured and euthanized on private properties with landowner permission.

“However, we do not encourage members of the public to ‘rescue’ cold-stunned iguanas by taking them indoors, or otherwise trying to warm them up,” she said. “They are wild animals and could act defensively once their body temperature rises.”

Other nonnative species may also be impacted by the cold weather, including

Burmese pythons (Python bivittatus). After the 2010 cold snap, many pythons were reported dead floating in the Everglades, Lessard said. But it can also negatively impact native marine species such as sea turtles, the Florida manatee (Trichechus manatus) and warm-water fish species.