Rumpless is a term used for the

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA replication, DNA or viral repl ...

which causes the tail of an animal to be absent. Usage and examples can be found in

Manx cat The Manx cat (, in earlier times often spelled Manks) is a breed of domestic cat (''Felis catus'') originating on the Isle of Man, with a naturally occurring mutation that shortens the tail. Many Manx have a small stub of a tail, but Manx cats ...

Manx Rumpy The Rumpless Game is a British breed of tail-less chicken. It may have originated on the Isle of Man, and may thus be known as the Manx Rumpy. There are both standard-sized and bantam Rumpless Game. History Manx Rumpy The British breed ...

Belgian d'Everberg The ( nl, Everbergse Baardkriel, italic=no), is a Belgian breed of bantam chicken. It is a tailless variant of the Barbu d'Uccle, and was bred in about 1906 at the Château d'Everberg, at Everberg in the municipality of Kortenberg, between Bru ...

and

Araucana The Araucana ( es, Gallina Mapuche, italic=no) is a breed of domestic chicken from Chile. Its name derives from the Araucanía region of Chile where it is believed to have originated. It lays blue-shelled eggs, one of very few breeds that do so. ...

chickens.

See also