You got me there! It's not the same animal. The one eating is a female, the other's a male. It's also kind of an optical illusion. The worm looks a lot bigger on the picture. While I took this picture I saw the male "yawning" and took his picture as well. So the idea of the big "Burp" was born.
Triturus species can manage big prey items though. The worm in the picture is (excuse me, was) longer than the carnifex, when it was outstretched. I do not allways feed them this way of course, but I never chop any worms.