Dominant Rumpless

The rumpless gene causes the chicken to have no tail feathers. It removes the oil gland on the tail, all of the tail feathers, and either one or two of the last spinal vertebrae on the bird. It can also cause a fusing of some of the lower spinal column in some cases too. Breeds with natural rumplessness include the Araucana, Piao, Kaulhuhn, and d'Everberg chickens. All of these breeds often have decreased fertility and hatch rates, likely due to skeletal reproductive issues (1) (3).

The mutation appears close to the same in both homozygous and heterozygous form, though most birds when tested are heterozygous, making many researchers believe that the homozygous form of the gene also causes lower hatch rates. (3)

The APA recognizes only one rumpless breed: the Araucana (2).

Breeding with Rumpless:

For more information about breeding with this kind of gene, including tips and tricks and a full explanation of how these results were calculated, please see here.

Rumpless x Rumpless = 100% Rumpless

Rumpless x het. Rumpless = 50% het. Rumpless, 50% Rumpless (all will be rumpless)

Rumpless x non-Rumpless = 100% het. Rumpless (all will look rumpless)

Het. Rumpless x het. Rumpless = 25% non-rumpless, 50% het. Rumpless, 25% full Rumpless (75% appear rumpless)

Het. Rumpless x non-Rumpless = 50% non-rumpless, 50% het. Rumpless (half of all chicks will not have a rump)