The iguanas start dropping out of the trees down here with the cold weather. They go into hibernation if it gets cold enough, and then they die if it doesn't warm up. A lot died last year.
I heard that the same thing happened to a lot of the pythons in the Everglades.
The best story I heard from last year was about a guy who drove around his neighborhood collecting the iguanas on the ground (apparently they can be quite tasty). He put them all into the back of his station wagon. Well, a number of them weren't dead yet, and as they warmed up they all awoke in his car.