An intrinsic mechanism for the co-existence of different survival strategies within mobile pastoralist communities Tomoo Okayasu a, * , Toshiya Okuro a , Undarmaa Jamsran b , Kazuhiko Takeuchi a a Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan b Center for Ecosystem Studies, Mongolian State University of Agriculture, Zaisan 53, Ulanbaatar 210153, Mongolia article info Article history: Received 9 April 2009 Received in revised form 7 December 2009 Accepted 15 December 2009 Available online 6 January 2010 Keywords: Mobile pastoralism Mobility Herders’ strategy Multi-agent model Mongolia Co-existence mechanism abstract In mobile pastoralism, strategies of mobility are highly heterogeneous within communities; some herd- ers are frequently mobile and others are not. Moreover, pastoral mobility changes over time, especially after external intervention. Although changes in the strategies of herders affect and are affected by other herders, the interactions between herders with different strategies and the effect of changes in the exter- nal environment on their strategies have not been explicitly studied. We examined such interactions with a multi-agent model, simulating the herders’ basic decision-making process, simplified rangeland ecosys- tem, and animal survival. The results showed clear co-existence of wealthy and poor herders at an inter- mediate cost of moving. The movement pattern revealed that an indirect interaction between wealthy and poor herders was the key to their co-existence, suggesting that very simple rules of pastoral mobility inherently contain a mechanism for the co-existence of wealthy and poor herders. At an intermediate cost of moving, the two groups have access to different pastures, thus reducing direct competition for poor herders and enabling their survival in drought years. Such interaction between herders suggests that any interventions in mobile pastoralist societies should take into account that impacts on the mobility of any one group can influence the entire social structure. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction In mobile pastoralism, mobility sustains the livelihoods of herd- ers by enabling access to forage of better quantity and quality to respond to intra- and inter-annual climatic fluctuations (Fernan- dez-Gimenez and Febre, 2006), and it enables them to survive disasters such as drought (Niamir-Fuller, 1998; Swift et al., 1996). But the utilities of mobility, diversity, and reciprocity are not homogeneous among herders. Baker and Hoffman (2006) ob- served a clear distinction between herders who were frequently mobile and those who were not. Wealthy and poor groups exhibit different livelihood strategies. Wealthier groups rely more on live- stock trading and home consumption for income whereas poor groups depend on casual wage labor and trade (Lesorogol, 2008). Differences in mobility between wealthy and poor herders have been widely observed, for example in Niger (McCarthy and Van- derlinden, 2004), Mongolia (Muller and Bold, 1996), Kazakhstan (Milner-Gulland et al., 2006), Ethiopia (Little et al., 2006), and South Africa (Baker and Hoffman, 2006). The herders’ strategies are highly heterogeneous within communities. This phenomenon has been frequently discussed as a poverty problem (Fernandez- Gimenez, 2001). Several studies (Bourbouze, 1999; Hitchcock, 1990; Cullis and Watson, 2005) have pointed out that wealthier herders not only have access to remote better pastures, but they also have access to the pasture in which poor herders live. Wealthy herders therefore derive unilateral benefits from communal pastureland. In addition to such heterogeneity, pastoral mobility has been historically subject to temporal change, especially in response to external forces such as changes in political regime, shifts towards a market economy, and climatic change and its effect on forage productivity. European colonization significantly impacted mobile pastoralists in Africa (Hary et al., 1996; Andriansen, 2008). Recent trends in pastoral management, such as privatization, forced sedentism, cultivation, and intensive livestock breeding have also changed herders’ movement restrictions and patterns (Hary et al., 1996). In former socialist nations such as Mongolia and Kazakhstan, the degradation of various infrastructures affected the mobility of herders (Fernandez-Gimenez, 2002; Milner-Gul- land et al., 2006). A number of studies has examined the impact of the external environment and herders’ adaptations to it on their living strate- gies (e.g., Sieff, 1999; Baker and Hoffman, 2006; Lesorogol, 2008), 0308-521X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.agsy.2009.12.006 * Corresponding author. Address: Laboratory of Landscape Ecology and Planning, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1- 1-1, Bunkyo-ku, Tokyo 113-8657, Japan. Tel.: +81 3 5841 5050; fax: +81 3 5841 5072. E-mail address: aokayasu@mail.ecc.u-tokyo.ac.jp (T. Okayasu). Agricultural Systems 103 (2010) 180–186 Contents lists available at ScienceDirect Agricultural Systems journal homepage: www.elsevier.com/locate/agsy