Ever seen iguanas falling from trees? Here's the science behind this bizarre phenomenon

The sight of non-native green iguanas falling off trees has become increasingly familiar, particularly during winters in Florida. While you may think of this as the cold-blooded reptiles having a clumsy moment, there's actually a fascinating reason behind it! According to Live Science, green iguanas have a difficult time regulating their body temperature in cold weather, which forces them to enter a temporary state of lethargy. The green iguanas experience brief paralysis that causes them to lose muscle control and hence they fall from trees or their perches. 

Joe Wsilewski, a conservation biologist at the University of Florida, revealed that iguanas often experience this kind of paralysis when the temperature dips into 40s Fahrenheit. Interestingly, the effect of temperature drop is just not evident just on the iguanas but also on other reptiles like pythons and crocodiles. "Their body metabolism is built for living in a tropical area. They have been placed in these habitats, south Florida for instance…where once or twice a year we get a cold snap," Wsilewski revealed to the outlet. 

The phenomenon of iguanas falling off from their nests has become more noticeable in recent times because their populations have also significantly increased. Iguanas were introduced to Florida in the 1960s, but their numbers have increased since the 1990s, partly because they have few natural predators. 

Notably, since the native range of these green reptiles extends from southern Mexico to central Brazil and Bolivia, their ideal body temperature is somewhere between about 85 and 95 degrees Fahrenheit (that is 29 to 35 degrees Celsius), as revealed by Wasilewski. The drop in temperature also affects negatively the iguanas' metabolism, and they start falling from trees once the temperature hits the low 40s. "I am getting more and more reports of counties north of where their northern extent is, starting to see [iguanas]. As the weather gets warmer they are going to distribute themselves to more northern counties; however, those more northern counties are going to have more cold snaps than southern Florida, and I don't think they'll be able to survive," Wasilewski revealed. 

While iguanas falling from trees might look harmless, it actually can negatively affect people, injuring people. It is pertinent to mention that the National Weather Service issues falling iguana warnings, urging people to be aware of their surroundings and, moreover, to leave a cold-stunned iguana undisturbed if they ever come across one.

Further, Wasilewski recalled being tasked with collecting cold-stunned iguanas, placing them in a box to warm up and then opening the box later to discover it teeming with highly active, jumping iguanas. "If nobody bothers them… chances are, they're gonna warm up and scurry right back up the tree," he said with the outlet. Meanwhile, Lisa Thompson, a spokesperson for the Florida Fish & Wildlife Conservation Commission shared that once these cold iguanas warm up, they will return back to their normal form. "Staff with the FWC's Nonnative Fish and Wildlife Program reminds the public that if they encounter a cold-stunned iguana, they should not bring it into their homes. Iguanas are wild animals and once they recover and warm up, they could act defensively," she added.