Wild Animal Circus is the name of a circus that either traveled through or is stationed in Duckburg.
The Wild Animal Circus is, as its name implies, a circus. Its focus seems to be its menagerie of wild animals, which include the gorilla Horrendo, its star actor, and at least two elephants. Its success, at least according to its manager, is greatly owed to the ferocious Horrendo and his feats of strength. This means, of course, that said manager was quite angry when barber Donald Duck "ruined" the ape in the early 1960's with his hair-cutting skills.
Behind the scenes
The Wild Animal Circus first appeared in Spare That Hair by Carl Barks. The story was released in May of 1963. Its name was never said out loud by any characters in the story, instead being garnered from a poster its manager shows to Donald Duck.