The only Time mine do this is just before the poop and they even make bubbles I. the water. I've not really listened to see if the fart periodically throughout the day, but most animals do because as you know the digestive process does produce Methane gas which does get expelled through the body.

Not all was probably flatulence though as these frogs also make popping/clicking noises which is their way of communicating and it doesn't come from their vent. They will also make a sound like this when they puff up full of air.

It is possible you were mistaken, but if it really was gas them perhaps you should look for alternatives in its diet.