Posted: Thu Sep 27, 2007 9:02 pm
When a turtle is ill it will have difficulty breathing and will yawn a lot or breath through an open mouth. A healthy turtle will occasionally yawn and may open his/her mouth to bite or hiss if threatened.
As for opening the mouth under water, turtles do this just to get a drink. Also, they may do this in play. For instance, my turtle will bite at the bubbles in the water and the stream of water itself when I'm adding water to his outside pond with the hose. It's just play.
If your turtle is active, has a good appetite, clear eyes, poops normally and doesn't seem to be having any difficulty breathing, then he's probably just a normal healthy turtle amusing himself. Does he have anything in the tank to interest him like river rocks, fake plants, a bridge, etc?
SpotsMama