This paper provides evidence for shifts in the species composition of Somali livestock herds, and offers possible explanations for such changes. Different species held together make efficient use of range vegetation, since camels and goats are primarily browsers, while cattle and sheep are largely grazers. A combination of different types of livestock also provides pastoral groups with a wide array of different animal products. Finally, herd diversification is an important strategy for household security in terms of ensuring minimum subsistence if one herd species is affected by disease, lack of drinking water or forage (Dahl 1981). Change in herd species can therefore have a significant impact on both rangeland ecosystems and pastoral production strategies.

The paper analyses the species composition of livestock herds and examines the ratios among herd species. The paper also shows how changes in herd composition have been caused by technical and economic factors such as the provision of new water supplies and changes in livestock export demand.

This work is based on a larger study (Al-Najim 1989) which employed several methods of data collection, including formal questionnaires, checklist surveys and informal discussions with local inhabitants and government officials. The topics discussed covered issues related to herd management techniques, water supply and veterinary care. Field work was conducted in 1984. Published and unpublished material on livestock numbers and livestock management practices was also consulted.