A couple of days ago I was sitting in the living room watching tv, and I heard a sound coming from my RES turtles tank. At first I didn't think anything of it, as I didn't think that turtles could make sounds. Then a few hours later, I heard the same sound, and realized it was actually one of the turtles. As he was swimming about the top of the water with his head poked out, he was making an almost quacking sound.
That was a few days ago, and it seems that he's making this sound more and more frequently. Is this normal, or should I be concerned?



