Iguanas fall from trees with cold snap KEY BISCAYNE, Fla. - How cold was it in South Florida this week? So cold the iguanas fell from the trees. The cold-blooded reptiles go into a deep sleep when the temperature falls into the 40s. Experts said their bodies basically shut off and they lose their grip on the tree. But it isn't sudden death: Experts said the reptiles perk up when the temperatures rises. The iguanas turn a gray hue in the meantime. Miami Metrozoo officials said the night cold causes the most drops. "The worst part of the cold comes in the evening, and they literally just shut off," said Ron Magill, communications director for Miami Metrozoo. "Their bodies shut off and they lose their grip on the tree, and they start falling." Temperatures hit the high 20s and low 30s this week in Florida during an unusual cold snap. While many of the iguanas will wake up, they could face death if low temperatures persist. Iguanas can sustain cold for between four and 10 hours before they have to wake up, Magill said. "The populations have expanded so drastically (that) when we do experience a really good cold snap, it will kill off a lot of them," said Kenneth Krysko, a herpetologist at the Florida Museum of Natural History at the University of Florida. "It is a good thing. They're not native, and they're considered a nuisance."