Let's break down the text accompanying the photograph:
Here's a photo I got from a friend...it's a 7-9 foot Cottonmouth that was killed out in the Fryer area of Caldwell County Kentucky the other day...be careful, these are deadly poisonous...to me this raises the question "Is this actually the biggest snake out there in the county? Or are there others that are bigger?" Ponder that next time you're in some tall weeds :) The man in the photo is (I've removed the name) and the photo was taken near the Fryer area of Caldwell...anyone who claims this is fake is an idiot.
Well, I've been called worse. But really, as I've explained before, it's not that the picture is fake, it is the information about the picture that is wrong.
Let's get the reported size out of the way. This snake is not nearly eight feet long. It appears longer than it really is because the snake is on a long stick and held much closer to the camera than the man holding the stick. If this the first time you've visited this blog, you can read about this trick here. I'll estimate that the snake is about five feet long (more on that later).
Let's move on to the identification. First: no Cottonmouth (Agkistrodon piscivorus) ever measured has reached over seven feet long (but you already knew that). Second: that's not a Cottonmouth. It's true that it can sometimes be hard to tell the difference between Cottonmouths and non-venomous water snakes but in this case, the dark bands on the tail give it away as a Diamondback Watersnake (Nerodia rhombifer). The largest known Diamondback Watersnake was just shy of six feet long (my source for this length is Snakes of the United States and Canada by Ernst and Ernst). Like all snakes within the genus Nerodia, Diamondback Watersnakes are harmless to people and primarily eat fish and amphibians. Females reach larger sizes than males (you can read why here) so we can be fairly confident that the snake in the picture is an old girl. As you might expect, Diamondback Watersnakes are often confused for Cottonmouths and killed as a result.
Finally, both Diamondback Watersnakes and Cottonmouths can be found in western Kentucky, leaving us no reason to doubt the location.