South Ethiopia's Omo River Valley is one of the world's most remote tribal areas. Some 15 semi-nomadic tribes inhabit the region. They are all agro-pastoralists. The Karo and Hamar tribes practice flood retreat cultivation. The Surma have raised the custom of body painting to an amazing art form. They practice a stick fighting called Donga which is very competitive. Many Nyangatom are nomadic, residing in mobile livestock villages that may migrate several times a year.