Although they are docile and come to be fed and get attention, they don't bond and show no interest in the affairs of people, and there are no domesticated moochs. What they eat when they don't get vegetable treats is unknown; some think they don't eat at all.
Moochs are the only known creatures to go to the seraph cities, but scholars are puzzled as to why and how.
"Our hallromm tribe showed the moochs what they thought of them getting all the attention from smut Fresian. We had to patch up half of them, but the moochs didn't come back. Which made our cargo hold goldfairy cry. The disorder of the cargo is unbelievable, and I'll need to fix the fairy's mood somehow."
— Sefinama, dustship captain
The German original, "Much", is a difficult phonetic translation; speak "mooch" with the same ending as Scottish "loch". So, yeah, flying rays, I couldn't stop myself, although it's a bit of a fantasy/sci-fi trope, but I love the shapes so much. There are places (in Africa, I think) where actual rays come to the shore to play with children and be petted, which is very, very cute, and I brought some of that into moochs' behaviour.