Grey Tree Frog

This little guy was sitting on the edge of a large tub of water the other day just singing his heart out (I don't really know if it is a he or a she). It took way too many tries to get him with his throat puffed out like this. The funniest thing is that I've seen these tiny frogs in the yard many times, usually either on a tree or sleeping in a flower pot during the heat of the day. They are always multiple shades of grey. This one is all green. They are loud all out of proportion with their size which is only about an inch and a half long. When I came back awhile later he was still sitting there but not singing and his color had turned back to grey. I first thought I had a new kind of frog, but it turns out that instead I have a frog that can change colors. He's not too afraid of me if I just keep a few feet away and even keeps singing when I'm around. I wish those really tee tiny Spring Peepers would do that. I still have never actually seen one of then, just hear them singing.
Jane