Rumplessness and ear tufts are separate inherited features

Araucanas can combine a tailless rump with feathered projections near the ears, but these are not one genetic package. Noorai and colleagues studied 60 birds from six American flocks in 2012, using genome-wide markers to investigate the two traits independently. They localized the rumpless-associated region to chromosome 2 and the tuft-associated region to chromosome 15.

The study identified candidate genes, including IRX1 and IRX2 in the rumpless region and TBX1 among the ear-tuft candidates. Candidate status means a promising research target, not a complete proof of the causative change. The paper also explains why mating outcomes are more complicated than picking two attractive parents: ear tuft inheritance is associated with embryo loss, and visible expression can vary. Its sample was selected to study traits, not to estimate national population size. These findings concern Araucana genetics; they should not be converted into a guaranteed hatch percentage for a keeper's flock.