ABSTRACT
Livestock mobility is the most important natural resource management strategy that East African pastoralists have engaged in to exploit resources in heterogeneous environments. For millennia, familiar norms of reciprocity among kin and friends facilitated effective movement. These traditional ties have always been nested (families within localities, localities within sections, alliances among sections, etc.), often ephemeral, and specific to particular groups and regions (Behnke, 1994; Galaty and Johnson, 1990; Mwangi and Ostrom, 2009). Sets of agreements at several social levels regulated the use of and access to resources. Informal social institutions were comprised of commonly observed practices with moral weight; when they were violated, sanctions followed. Land was held communally, and fuzzy (indefinite and seasonally moving) boundaries, rules and behaviour were the norm in arid and semi-arid regions, where opportunistic strategies allowed herders to take advantage of patchy resources, characterised by large areas of low productivity land and sparse, rich, key resources (Swallow and Bromley, 1995).
