[jiggyboy]

The Sun-Sentinel nailed it, the iguanas are not quite dropping dead, but they are falling out of the trees:

Kamikaze iguanas fall from Florida's frozen trees

The lizards go into a type of hibernation when the temperature drops below around 9 degrees C, all body functions but the heart switching off and blood flow cut to a minimum.

It means they lose their grip on branches and the creatures, which are common in the "sunshine state", plunge out of the trees.

The lizards, which can grow up to five feet long, then lie grey and appear dead until the temperature rises again, at which time they usually revive.

http://www.telegraph.co.uk/news/worldnews/northamerica/usa/6947254/Kamikaze-iguanas-fall-from-Floridas-frozen-trees.html

I was going to post this as an article but when I searched and found this thread I decided to just ping everybody here.

[jiggyboy]

Whoops, looks like the Telegraph swiped a few paragraphs from the Sun-Sentinel article. The bit about killing them humanely and the quote from Tiffany Snow (!) are verbatim.