Both groups are traditionally pastoralists, whose migration patterns take them north into the Sahara during the brief rainy season, and south as far as Nigeria and Burkina Faso during the dry season. Like all Tuareg groups, they are formed from a number of highly stratified castes, who interweave loyalty from a number of clans, some of whom are limited to specific castes. Ruling caste clans lead the large confederations, and engage in seasonal migration, herding, trade, war, and religious duties. Lower castes, and clans made up of subject groups of free clans are more likely sedentary and not part of confederations, even if their traditional suzerains are members of a confederation such as the Iwellemmedan. In addition, large confederations may include allied non-Tuaregs, such as local Arabic speaking tribes.