Human Ecology

, Volume 45, Issue 4, pp 525–532 | Cite as

No Magic Number: an Examination of the Herd-Size Threshold in Pastoral Systems Using Agent-Based Modeling

  • Mark MoritzEmail author
  • Abigail Buffington
  • Andrew J. Yoak
  • Ian M. Hamilton
  • Rebecca Garabed


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.


Agent-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.


  1. Barth F. (1961). Nomads of South Persia: The Basseri tribe of the Khamseh confederacy, Little, Brown and Company, Boston (MA).Google Scholar
  2. 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
  3. Bradburd D. A. (1980). Never Give a Shepherd an Even Break: Class and Labor among the Komachi. American Ethnologist 7(4): 603–620.CrossRefGoogle Scholar
  4. Bradburd D. A. (1982). Volatility of Animal Wealth among Southwest Asian Pastoralists. Human Ecology 10(1): 85–106.CrossRefGoogle Scholar
  5. Bradburd D. A. (1989). Producing their Fates: Why Poor Basseri Settled but Poor Komachi and Yomut Did Not. American Ethnologist 16(3): 502–518.CrossRefGoogle Scholar
  6. 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
  7. Coulomb, J.( 1974). Methodes d'analyse statistique du troupeau. Paper read at Journees techniques: Production animale, at Paris.Google Scholar
  8. 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
  9. Fratkin E., and Roth E. A. (1990). Drought and Economic Differentiation among Ariaal Pastoralists of Kenya. Human Ecology 18(4): 385–402.CrossRefGoogle Scholar
  10. Grandin B. E. (1989). Labor Sufficiency, Livestock Management, and Time Allocation on Maasai Group Ranches. Research in Economic Anthropology 11: 143–178.Google Scholar
  11. Grimm V., Revilla E., Berger U., Jeltsch F., Mooij W. M., Railback S. F., Thulke H.-H., Weiner J., Wiegand T., and DeAngelis D. L. (2005). Pattern-Oriented Modeling of Agent-Based Complex Systems: Lessons from Ecology. Science 310(11 November 2005): 987–991.CrossRefGoogle Scholar
  12. 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
  13. 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
  14. Heffernan C., and Rushton J. (2000). Restocking: A Critical Evaluation. Nomadic Peoples 4(1): 110–124.CrossRefGoogle Scholar
  15. Loftsdóttir K. (2008). The Bush is Sweet: Identity, Power, and Development among WoDaaBe Fulani in Niger, Nordiska Afrikainstituted, Uppsala (Sweden).Google Scholar
  16. Lybbert T., Barrett C., Desta S., and Coppock L. (2005). Stochastic Wealth Dynamics and Risk Management among a Poor Population. Economic Journal 114: 750–777.CrossRefGoogle Scholar
  17. Mace R., and Houston A. (1989). Pastoralist Strategies for Survival in Unpredictable Environments: A Model of Herd Composition that Maximises Household Viability. Agricultural Systems 31(2): 185–204.CrossRefGoogle Scholar
  18. McCabe J. T. (1987). Drought and Recovery: Livestock Dynamics among the Ngisonyoka Turkana of Kenya. Human Ecology 15(4): 371–389.CrossRefGoogle Scholar
  19. McPeak J. G., and Barrett C. B. (2001). Differential Risk Exposure and Stochastic Poverty Traps among East African Pastoralists. American Journal of Agricultural Economics 83(3): 674–679.CrossRefGoogle Scholar
  20. Mitchell M. (2009). Complexity: A Guided Tour, Oxford University Press, Oxford (UK).Google Scholar
  21. Moris J. R. (1988). Oxfam's Kenya Restocking Projects. ODI Pastoral Development Network paper 26c: 1–21.Google Scholar
  22. 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
  23. 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
  24. Raikes P. L. (1981). Livestock Development and Policy in East Africa, Scandinavian Institute of African Studies, Uppsala (Sweden).Google Scholar
  25. Railsback S. F., and Grimm V. (2012). Agent-Based and Individual-Based Modeling: A Practical Introduction, Princeton University Press, Princeton (NJ).Google Scholar
  26. Reynolds C. W. (1987). Flocks, Herds, and Schools: A Distributed Behavioral Model. Computer Graphics 21(4): 25–34.CrossRefGoogle Scholar
  27. Roth E. A. (1996). Traditional Pastoral Strategies in a Modern World: An Example from Northern Kenya. Human Organization 55(2): 219–224.CrossRefGoogle Scholar
  28. Sieff D. F. (1999). The Effects of Wealth on Livestock Dynamics among the Datoga Pastoralists of Tanzania. Agricultural Systems 59: 1–25.CrossRefGoogle Scholar
  29. Silverman E., Bijak J., Hilton J., Cao V. D., and Noble J. (2013). When Demography Met Social Simulation: A Tale of Two Modelling Approaches. Journal of Artificial Societies and Social Simulation 16(4): 9.CrossRefGoogle Scholar
  30. 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
  31. Sutter J. W. (1987). Cattle and Inequality: Herd Size Differences and Pastoral Production among the Fulani of Northeastern Senegal. Africa 57(2): 196–218.CrossRefGoogle Scholar
  32. 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
  33. 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
  34. Wilensky U. (1999). NetLogo. Center for Connected Learning and Computer-Based Modeling, Northwestern University. Evanston, IL.

Copyright information

© Springer Science+Business Media, LLC 2017

Authors and Affiliations

  1. 1.The Ohio State UniversityColumbusUSA
  2. 2.Otterbein UniversityWestervilleUSA

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