Influence of Rainfall Fluctuations on Population Trends of Eleven Wild Herbivores in Soysambu Conservancy, Kenya

  • Johnstone K. Kimanzi Department of Wildlife Management, School of Natural Resources Management University of Eldoret P.O. BOX 1125, Eldoret, Kenya
  • Caroline W. Mbau Department of Wildlife Management, School of Natural Resources Management University of Eldoret P.O. BOX 1125, Eldoret, Kenya
Keywords: Population trends; Rainfall fluctuations; Soysambu conservancy; Wild herbivores.


Recent studies have shown that about 70% of wildlife populations are found outside the protected areas in Kenya. In a bid to cater for this large portion of wildlife many conservancies have been established in Kenya.  Soysambu is one of the private conservancies that has experienced consistent decline in rainfall during the dry seasons. This may cause decline in wildlife populations in this conservancy as their declines have been shown to be directly correlated with decreases in rainfall unlike in other private conservancies. This study was carried out to determine the population trends of eleven wild herbivores, the effect of temporal variation in rainfall on wild herbivore populations and establish the relationship between wild herbivore populations in Soysambu conservancy. Data for twentyone years (1993-2013) on rainfall and wild herbivore populations were obtained from the conservancy records and the Kenya meteorology service. Regression and correlation analyses were used to assess population trends, relationship between rainfall parameters (wet season, dry season, mean annual, and 5-year cumulative rainfalls) and herbivore populations, and correlation among herbivore populations. Results showed a significant increase in the population of impala (r2 = 0.267, P = 0.004), buffalo (r2 = 0.511, P < 0.001), zebra (r2 = 0.745, P < 0.001), giraffe (r2 = 0.786, P < 0.001), herbivore browsers (r2 = 0.5641, P < 0.001) and grazers (r2 = 0.748, P < 0.001), but a significant decrease in the population of Thomson’s gazelle (r2 = 0.387, P = 0.007). The significant increase in the populations of zebra, giraffe and all grazers were attributed to the increase in mean annual rainfall and decrease in dry season rainfall. Also, the significant decrease in the population of Thomson’s gazelle was attributed to the significant decrease in dry season rainfall (r2 = 0.321, P = 0.022) and the increase in the populations of zebra (r = -0.654, n = 21, p = 0.040) and giraffe (r = -0.654, n = 21, P = 0.001). The increase in the other herbivore populations could not be explained by rainfall variability. Pearson correlation showed that there was a significant positive correlation between browsers and grazers (r = 0.745, n = 21, P < 0.001) and significant correlations (P < 0.05) among 10 wild herbivore species. For sustainable conservation of diverse wild herbivores in Soysambu conservancy there is need to (i) provide artificial water supply to species that are water-dependent and significantly decreasing to counter the adverse effects of drought, (ii) regulate the populations that are significantly increasing at the expensive of others and (iii) carry out further research to understand habitat requirements of the various herbivore species and identify resource inadequacies before they threaten population viability.


Annals of the New York Academy of Sciences, 1223, 120–128.

Borner, M., Fitz Gibbon, C. D., Borner, M., Caro, T. M., Lindsay, W.K., Collins, D. A. & Holt, M. E. (1987) The decline of the Serengeti Thomson's gazelle population. Oecologia 73:32-40.

Buckland, S. T., Anderson, D. R., Burnham, K. P., Laake, J. L., Borchers, D. L., and Thomas, L. (2001) Introduction to Distance Sampling, Oxford University Press, Oxford.

Collen, B., Loh, J., Whitmee, S. & McRae, L. (2009) Monitoring changes in vertebrate abundance: the Living Planet Index. Conservation Biology, 23,317–327

Craigie, I. D., Baillie, J. E., Balmford, A., Carbone, C., Collen, B., Green, R. E., & Hutton, J. M. (2010). Large mammal population declines in Africa’s protected areas. Biological Conservation, 143(9), 2221-2228.
Dwight, P. (2005). "Lake Elmenteita added to the Ramsar List". The Ramsar Convention on Wetlands. Available at:
FAO (2017) Sustainable Wildlife Management and Human−Wildlife Conflict. Available at: Accessed: 27 June 2017 2009-04-19.

Illius, A.W. & T G. O'Connor. (2000). Resource heterogeneity and ungulate population dynamics. Oikos 89: 283-294.

IUCN (1974) Classification and Use of Protected Natural and Cultural Areas, IUCN Occasional Paper No. 4, IUCN, Morges, Switzerland.

IUCN (2016). An Introduction to the IUCN Red List of Ecosystems: The Categories and Criteria for Assessing Risks to Ecosystems. Gland, Switzerland: IUCN. vi + 14pp.

Kenya Wildlife Conservancies Association (2015). Kenya wildlife conservancies association (KWCA) flyer 2015. Fact sheet.

Kenya Wildlife Conservancies Association (2016). State of wildlife conservancies in Kenya report 2016. Annual Report.

Kimanzi, J. K. and Wishitemi, B. E. L. (2001) The effect of land-use changes on herbivores of Masai Mara Ecosystem. International Journal of Environmental Studies, 58:727-740.

Kimanzi, J. K. and Wishitemi, B. E. L. (2003) The effect of land-use / cover changes on Wildlife Depredation in Masai Mara Ecosystem. International Journal of Environmental Studies, 60(5):453-461.

Kimanzi, J. K., Wanyingi, J. N., Ipara, H. & Odwori, P.O. (2016). Factors influencing population dynamics of five antelope species in Ruma National Park, Kenya. African Journal of Education, Science and Technology, 3(1), 59-70.

Knight, J. (2017). The Basics of Wildlife Management. Available at:

Kruger National Park (2016) Reedbuck. Available at: http:/ (Accessed: 24 May 2016).

Leap (2019) Soysambu Conservancy conservation management plan. Available at: (Accessed: 7 February 2019).

Loftis, E. E. (2015). Population Viability of Mega-Herbivores in Manyara Ranch, Tanzania, in a Climate Change Context.

Mawdsley, J. R., O’Malley, R. O. B. I. N., & Ojima, D. S. (2009). A review of climate‐change adaptation strategies for wildlife management and biodiversity conservation. Conservation Biology, 23(5), 1080-1089.

Ogutu, J. O., & Owen‐Smith, N. (2003). ENSO, rainfall and temperature influences on extreme population declines among African savanna ungulates. Ecology Letters, 6(5), 412-419.

Ogutu, J. O., & Owen‐Smith, N. (2005). Oscillations in large mammal populations: are they related to predation or rainfall? African Journal of Ecology, 43(4), 332-339.

Ogutu, J. O., Piepho, H. P., Said, M. Y., & Kifugo, S. C. (2014). Herbivore dynamics and range contraction in Kajiado County Kenya: climate and land use changes, population pressures, governance, policy and human-wildlife conflicts. The Open Ecology Journal, 7(1).

Ogutu, J.O., Piepho, H.P., Said, M.Y., Ojwang, G.O., Njino, L.W., Kifugo, S.C., Wargute, P.W. (2016). Extreme Wildlife Declines and Concurrent Increase in Livestock Numbers in Kenya: What Are the Causes? PLoS One. 27;11(9):e0163249. doi: 10.1371/ journal.pone.0163249.

Owen-Smith, N. and Mills, M. G. L. (2006) 'Manifold Interactive Influences on the Population Dynamics of a Multispecies Ungulate Assemblage', Ecological Monographs, 76(1),73-92.

Owen-Smith, R. N. (2002). Adaptive herbivore ecology: from resources to populations in variable environments. Cambridge University Press.

Parker D. M & Bernard, R. T. F. (2005). The diet and ecological role of giraffe (Giraffe camelopadarlis) introduced to the eastern cape, South Africa. Journal of Zoological Society of London 267:203-210.

Ripple, W. J., Newsome, T. M., Wolf, C., Dirzo, R., Everatt, K. T., Galetti, M., Hayward, M. W., Kerley, G. I. H., Levi, T., Lindsey, P. A., Macdonald, D. W., Malhi, Y., Painter L.E., Sandom, C. J., Terborgh, J., & Blaire Van Valkenburgh, R. (2015) Collapse of the world’s largest herbivores. American Association for the Advancement of Science.

Sampere, E. and Kinuthia, W. (2012) Lewa Wildlife Conservancy Annual Report 2012. Ascent Limited.

Vigne, R. (2017) Ol Pejeta Conservancy Annual report 2017.

Western, D., Russell, S., & Cuthill, I. (2009). The status of wildlife in protected areas compared to non-protected areas of Kenya. PLoS One, 4(7), e6140.
Wildlife Fund, Harare, Zimbambwe.

Wildlife Safari (2016) African Animals. Available at: http:/ (Accessed: May 24 2016).

Wilkie, D.S., Bennett, E.L., Peres, C.A. & Cunningham, A.A. (2011) The empty forest revisited.

World Wildlife Fund (2000). Counting Wildlife Manual. Wildlife Management Series. World

World Wildlife Fund (2014). The Living Planet Index. In: Living Planet Report 2014 (Eds: R. McLellan, L. Iyengar, B. Jeffries, N. Oerlemans, M. Grooten, M. Guerraoui, & P. Sunters). WWF International, Gland, Switzerland
How to Cite
Kimanzi, J., & Mbau, C. (2019, September 17). Influence of Rainfall Fluctuations on Population Trends of Eleven Wild Herbivores in Soysambu Conservancy, Kenya. African Journal of Education,Science and Technology, 5(2), 1-11. Retrieved from