Mergotery feeds mainly on fish (hence the name: Mergus - merganser, duck piscivorous) can hunt small animals, swimming across the river, and catch young waterfowl. Perhaps carnivorous marsupials more preadapted to transition to food fish, but the bag prevents them master the aquatic environment, so mergotery not met worthy competitors in Australian rivers. Only fish can compete with them for food. From platypus mergotery in larger dimensions: it grows up to a meter in length; about half the length of the tail, flattened and widened at the end.