From Creatures Wikia
Uglee (Bruttoia albiania)Albian Grendel. It spends most of its time asleep, on the barren ledge in the Desert Terrarium - when it is awake, it is often sailing about its home in search of Gnarler eggs. As disgusting as they appear, however, they are harmless to creatures.
Two uglees are placed in the Desert at the beginning of the game. They do not reproduce. More can be obtained through cloning, however their collision detection does not work well in any terrarium other than the desert, and they invariably end up forever flying into the wall in the top corner of whichever other one they are placed into.