No Magic Number: an Examination of the Herd-Size Threshold in Pastoral Systems Using Agent-Based Modeling
Pastoralists who depend on their herds for their livelihoods need a minimum number of animals to support their household. Due to the dynamics of herd growth, pastoralists may find themselves at times below that minimum number. Previous studies have shown that there is a herd-size threshold below which households are unlikely to escape poverty. We explore the concept of a herd-size threshold using an agent-based model to examine the role of scale and stochasticity in family herd dynamics. The model was parametrized with data from the literature. The results from the computer simulations show (1) that offtake rates significantly limit herd growth; and (2) that herd-size threshold is better understood as a range of probabilities. We discuss the methodological and conceptual advantages of using agent-based modeling to examine demographic dynamics, including the possibility of conducting multiple experiments in silico to examine the dynamics of herd growth.
KeywordsAgent-based model Demography Threshold Family herds African pastoral systems
Compliance with Ethical Standards
This research project was supported by a grant from the National Science Foundation (BCS-1546061).
Conflict of Interest
The authors declare that they have no conflict of interest.
- Barth F. (1961). Nomads of South Persia: The Basseri tribe of the Khamseh confederacy, Little, Brown and Company, Boston (MA).Google Scholar
- Borgerhoff Mulder M., and Sellen D. W. (1994). Pastoralist decisionmaking: A behavioral ecological perspective. In Fratkin E., Galvin K. A., and Roth E. A. (eds.), African Pastoralists Systems: An Integrated Approach, Lynne Rienner publishers, Boulder (CO).Google Scholar
- Buffington, A., Yoak, A. J., Hamilton, I.M., Garabed, R., and Moritz, M.. (2016). Family herd model (version 1). CoMSES Computational Model Library.Google Scholar
- Coulomb, J.( 1974). Methodes d'analyse statistique du troupeau. Paper read at Journees techniques: Production animale, at Paris.Google Scholar
- Dahl G., and Hjort A. (1976). Having Herds: Pastoral Herd Growth and Household Economy, Stockholm Studies in Social Anthropology, Department of Social Anthropology, University of Stockholm, Stockholm (Sweden).Google Scholar
- Grandin B. E. (1989). Labor Sufficiency, Livestock Management, and Time Allocation on Maasai Group Ranches. Research in Economic Anthropology 11: 143–178.Google Scholar
- Grimm V., Berger U., Bastiansen F., Eliassen S., Ginot V., Giske J., Goss-Custard J., Grand T., Heinz S. K., and Huse G. (2006). A standard protocol for describing individual-based and agent-based models. Ecological Modelling 198(1–2):115–126.Google Scholar
- Grimm V., Berger U., DeAngelis D. L., Polhill J. G., Giske J., and Railsback S. F. (2010). The ODD protocol: A review and first update. Ecological Modelling 221(23):2760–2768.Google Scholar
- Loftsdóttir K. (2008). The Bush is Sweet: Identity, Power, and Development among WoDaaBe Fulani in Niger, Nordiska Afrikainstituted, Uppsala (Sweden).Google Scholar
- Mitchell M. (2009). Complexity: A Guided Tour, Oxford University Press, Oxford (UK).Google Scholar
- Moris J. R. (1988). Oxfam's Kenya Restocking Projects. ODI Pastoral Development Network paper 26c: 1–21.Google Scholar
- Moritz, M. (2003). Commoditization and the pursuit of piety: The transformation of an African pastoral system. Dissertation, Department of Anthropology, University of California at Los Angeles, Los Angeles.Google Scholar
- Njoya A., Bouchel D., Ngo Tama A.-C., Moussa C., Martrenchar A., and Letenneur L. (1997). Systèmes d'élevage et productivité des bovins en milieu paysan. World Animal Review 89(2): 12–23.Google Scholar
- Raikes P. L. (1981). Livestock Development and Policy in East Africa, Scandinavian Institute of African Studies, Uppsala (Sweden).Google Scholar
- Railsback S. F., and Grimm V. (2012). Agent-Based and Individual-Based Modeling: A Practical Introduction, Princeton University Press, Princeton (NJ).Google Scholar
- Stenning D. J. (1958). Household viability among the pastoral Fulani. In Goody J. (ed.), The Development Cycle in Domestic Group, Cambridge University Press, Cambridge.Google Scholar
- Wagenaar K. T., Diallo A., and Sayers A. R. (1986). Productivity of Transhumant Fulani Cattle in the Inner Niger delta of Mali, ILCA Research Report; No. 13, International livestock Centre for Africa, Addis Ababa, Ethiopia.Google Scholar
- Wilensky U., and Rand W. (2015). An Introduction to Agent-Based Modeling: Modeling Natural, Social, and Engineered Complex Systems with NetLogo, MIT Press, Cambridge (MA).Google Scholar
- Wilensky U. (1999). NetLogo. Center for Connected Learning and Computer-Based Modeling, Northwestern University. Evanston, IL. http://ccl.northwestern.edu/netlogo/.