AS night falls over the vast Yirol plains, and the hundreds of long-horned cattle settle at their tethers, the sound of singing floats up from a smoke-shrouded camp.
A tall cattleman stands in the midst of his herd beside a cow-dung fire, singing to his largest bull.
The scene is doubtless repeated in cattle camps throughout Bahr el Gazal, the remote central region of southern Sudan inhabited by the Dinka, the country's largest and most colorful tribe.
As in most pastoral communities, Dinka life centers around cattle, the providers of food, wealth, and status. But the Dinka have extended appreciation of their animals far beyond most other tribes to the point of cattle worship.
A Dinka may spend all day with his favorite bull, brushing ash into his coat to ward off flies and polishing its curving horns with oil extracted from the nut of a local tree.
A man buys his wife with cattle and he names his first-born son after his best bull.
This ancient way of life, however, has undergone more changes over the past decade than in several previous centuries. The reason is Sudan's 14-year-old civil war between the black African south and the Arab Islamic north.
On one recent morning, a group of Dinka men left their cattle camp at dawn, armed with an assortment of traditional weapons, spears, and mahogany clubs, as well as several rusty-looking guns. Word had spread of a pending attack by rival Nuer tribesmen on a neighboring cattle camp. Reinforcements were needed.
Incursions by heavily armed Nuer into Dinka territory have become frequent. On March 17, for example, a Nuer raid left 19 people dead, 30 wounded, and 5,000 head of cattle stolen.
The Dinka form the backbone of the rebel Sudan People's Liberation Army (SPLA), led by John Garang. This month his rival, Riak Machar, signed a "political charter" with the Islamic government in Khartoum, confirming allegations that his Nuer forces had been fighting alongside those of the government ever since Mr. Machar split from the SPLA in 1991.
Traditional rivalry between Dinka and Nuer has been exacerbated by current politics and modern weaponry. The Dinka have exacted their revenge for the damaging Nuer raids, as in the attack on Ganyiel last July in which up to 200 people were killed.
Meanwhile, the main towns in Yirol and Rumbek counties are occupied by Sudanese government troops. Services there have been cut off, depriving the population of education, health care, and agricultural support.
Under British colonial rule, little effort was wasted on trying to bring development to the uncharted areas beyond the few insignificant towns. Without roads and river bridges, the majority of people are inaccessible for nine months of the year.
Deep in papyrus swamps along the White Nile that swarm with mosquitoes, Dinka fishermen eke out a living using dugout mahogany canoes and spears.
River trade with the capital Khartoum ceased when war broke out. The few fishing nets in use are made from yarn supplied by the Red Cross. Many Dinka have never seen soap or salt.
IT was here that early Christian missionaries from Italy set up their southernmost mission on the Nile in 1854 at Shambe, 1,000 miles south of Khartoum.
"We are Christians here," says Dinka chief Abraham Abuk. "We pray for the end of hunger and disease and for freedom from the Arabs."
Norwegian People's Aid (NPA), one of the few international aid agencies that has ventured this far into southern Sudan, is trying to encourage agricultural diversity among the Dinka to compensate for the damage the war has caused to their economy.
Most families cultivate small patches of sorghum and groundnuts to supplement their milk diet, but farming methods are poor.
"It's an enormous cultural challenge," says Dan Eiffe of NPA. "The Dinka tell us they want change.
"But try asking a cattleman to use his bull to pull a plow. He'd rather use his wife first."