Skip to main content
SpringerLink
Log in

Droughts Decouple African Savanna Grazers from Their Preferred Forage with Consequences for Grassland Productivity

  • Published:
Ecosystems Aims and scope Submit manuscript

Abstract

Grazing lawn and flammable-tussock grass communities are contrasting resource pools for mammalian grazers in terms of forage quantity and quality. Drought events fundamentally alter forage availability within these communities and therefore should alter herbivore use with repercussions for the recovery and functioning of ecosystems after drought. During and after an intense El Niño drought (2014–2017) in Kruger National Park, South Africa, we addressed two questions: (1) how does herbivore use of different grass types change during a drought and (2) how do these changes affect grass productivity post-drought? We monitored grazer use of three different grass communities (lawn, tussock and burned-tussock) at a landscape scale and measured primary productivity monthly during and post-drought. For the first drought year, grazer numbers were highest on grazing lawn communities. This pattern continued into the second dry growing season, until herbivores finally left the study area. Both lawns and tussock grasslands recovered rapidly after the first good rainfall (productivity > 150 g m−2 per month). However, grazers did not return to feed on the same patches they had frequented pre-drought resulting in grazing lawn grasses self-shading and senescing. Longer droughts have the potential to decouple grazers and grazing lawns with negative impacts on lawn productivity and persistence that could drive the loss of lawns in savanna landscapes and impact mesoherbivore populations. It is clear from our results that grazer effects need to be incorporated into drought frameworks to understand the consequences of droughts for grassland function.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Figure 1
Figure 2
Figure 3
Figure 4
Figure 5

Similar content being viewed by others

Data Availability

Data have been submitted to South African National Parks (SANParks) online data repository http://dataknp.sanparks.org/sanparks/metacat/judithk.111311.2/sanparks.

References

  • Anderson TM, Hopcraft JGC, Eby SL, Ritchie M, Grace JB, Olff H. 2010. Landscape-scale analyses suggest both nutrient and antipredator advantages to Serengeti herbivore hotspots. Ecology 91:1519–29. http://www.ncbi.nlm.nih.gov/pubmed/20503883. Accessed 27 Jan 2015.

  • Anderson TM, Kumordzi BB, Fokkema W, Valls Fox H, Olff H. 2013. Distinct physiological responses underlie defoliation tolerance in African lawn and bunch grasses. Int J Plant Sci 174:769–778.

    Google Scholar 

  • Archibald S, Bond WJ. 2004. Grazer movements: Spatial and temporal responses to burning in a tall-grass African savanna. Int J Wildl Fire 13:377–85.

    Google Scholar 

  • Archibald S, Bond WJ, Stock WD, Fairbanks DHK. 2005. Shaping the landscape: fire-grazer interactions in an African savanna. Ecol Appl 15:96–109.

    Google Scholar 

  • Arnold SG, Anderson TM, Holdo RM. 2014. Edaphic, nutritive, and species assemblage differences between hotspots and matrix vegetation: two African case studies. Biotropica 46:387–94.

    Google Scholar 

  • Augustine DJ. 2004. Influence of cattle management on habitat selection by impala on central Kenyan rangeland. J Wildl Manag 68:916–23.

    Google Scholar 

  • Augustine DJ, McNaughton SJ. 2006. Interactive effects of ungulate herbivores, soil fertility, and variable rainfall on ecosystem processes in a semi-arid savanna. Ecosystems 9:1242–56.

    CAS  Google Scholar 

  • Augustine DJ, McNaughton SJ, Frank DA. 2003. Feedbacks between soil nutrients and large herbivores in a managed savanna ecosystem. Ecol Appl 13:1325–37.

    Google Scholar 

  • Bates D, Mächler M, Bolker BM, Walker SC. 2015. Fitting linear mixed-effects models using lme4. J Stat Softw 325:883–5. http://www.sciencemag.org/cgi/doi/10.1126/science.1176170. Accessed 17 Oct 2017.

  • Biondini ME, Patton BD, Nyren PE. 1998. Grazing intensity and ecosystem processes in northern-mixed grass prairie, USA. Ecol Appl 8:469–79.

    Google Scholar 

  • Bond WJ, Keeley JE. 2005. Fire as a global ‘herbivore’: the ecology and evolution of flammable ecosystems. Trends Ecol Evol 20:387–94. http://www.ncbi.nlm.nih.gov/pubmed/16701401. Last accessed 15/06/2011.

  • Bonnet O, Fritz H, Gignoux J, Meuret M. 2010. Challenges of foraging on a high-quality but unpredictable food source: the dynamics of grass production and consumption in savanna grazing lawns. J Ecol 98:908–16. http://doi.wiley.com/10.1111/j.1365-2745.2010.01663.x. Last accessed 24/02/2012.

  • Briggs JM, Knapp AK. 1995. Interannual variability in primary production in tallgrass prairie: climate, soil moisture, topographic, and fire as determinants of aboveground biomass. Am J Bot 82:1064–9.

    Google Scholar 

  • Buis GM, Blair JM, Burkepile DE, Burns CE, Chamberlain AJ, Chapman PL, Collins SL, Fynn RWS, Govender N, Kirkman KP, Smith MD, Knapp AK. 2009. Controls of aboveground net primary production in mesic savanna grasslands: an inter-hemispheric comparison. Ecosystems 12:982–95.

    CAS  Google Scholar 

  • Burkepile DE, Burns CE, Tambling CJ, Amendola E, Buis GM, Govender N, Nelson V, Thompson DI, Zinn AD, Smith MD. 2013. Habitat selection by large herbivores in a southern African savanna: the relative roles of bottom-up and top-down forces. Ecosphere 4:1–19.

    Google Scholar 

  • Codron D, Codron J, Lee-Thorp JA, Sponheimer M, de Ruiter D, Sealy J, Grant R, Fourie N. 2007. Diets of savanna ungulates from stable carbon isotope composition of faeces. J Zool 273:21–9. http://doi.wiley.com/10.1111/j.1469-7998.2007.00292.x. Last accessed 28/06/2011.

  • Crawley MJ, Ed. 2012. The R book. West Sussex: Wiley.

    Google Scholar 

  • Cromsigt JPGM, te Beest M. 2014. Restoration of a megaherbivore: landscape-level impacts of white rhinoceros in Kruger National Park, South Africa. J Ecol 102:566–75.

    Google Scholar 

  • Cromsigt JPGM, Olff H. 2008. Dynamics of grazing lawn formation: an experimental test of the role of scale-dependent processes. Oikos 117:1444–52.

    Google Scholar 

  • Cromsigt JPGM, Rensburg SJ, Etienne RS, Olff H. 2009. Monitoring large herbivore diversity at different scales: comparing direct and indirect methods. Biodivers Conserv 18:1219–31. http://www.springerlink.com/index/10.1007/s10531-008-9506-1. Last accessed 28/08/2011.

  • Fay PA, Carlisle JD, Knapp AK, Blair JM, Collins SL. 2003. Productivity responses to altered rainfall patterns in a C4-dominated grassland. Oecologia 137:245–51.

    PubMed  Google Scholar 

  • Frank DA, Kuns MM, Guido DR. 2002. Consumer control of grassland plant production. Ecology 83:602–6.

    Google Scholar 

  • Fuhlendorf SD, Engle DM. 2001. Restoring heterogeneity on rangelands: ecosystem management based on evolutionary grazing patterns. Bioscience 51:625.

    Google Scholar 

  • Fuhlendorf SD, Engle DM, Kerby J, Hamilton R. 2009. Pyric herbivory: rewilding landscapes through the recoupling of fire and grazing. Conserv Biol 23:588–98.

    PubMed  Google Scholar 

  • Gertenbach WPD. 1983. Landscapes of the Kruger National Park. Koedoe 26:9–121.

    Google Scholar 

  • Gizaw MS, Gan TY. 2017. Impact of climate change and El Niño episodes on droughts in sub-Saharan Africa. Clim Dyn 49:665–82.

    Google Scholar 

  • Hema EM, Di Vittorio M, Barnes RF, Guenda W, Luiselli L. 2017. Detection of interannual population trends in seven herbivores from West African savannah: a comparison between dung counts and direct counts of individuals. Afr J Ecol 55:609–17.

    Google Scholar 

  • Hempson GP, Archibald S, Bond WJ, Ellis RP, Grant CC, Kruger FJ, Kruger LM, Moxley C, Owen-Smith N, Peel MJS, Smit IPJ, Vickers KJ. 2015. Ecology of grazing lawns in Africa. Biol Rev 90:979–94. http://rstb.royalsocietypublishing.org/lookup/doi/10.1098/rstb.2015.0309. Accessed 20 Sept 2016.

  • Kleynhans EJ, Jolles AE, Bos MRE, Olff H. 2010. Resource partitioning along multiple niche dimensions in differently sized African grazers. Oikos 120:591–600.

    Google Scholar 

  • Knapp AK, Hoover DL, Blair JM, Buis GM, Burkepile DE, Chamberlain A, Collins SL, Fynn RWS, Kirkman KP, Smith MD, Blake D, Govender N, O’Neal P, Schreck T, Zinn A. 2012. A test of two mechanisms proposed to optimize grassland aboveground primary productivity in response to grazing. J Plant Ecol 5:357–65.

    Google Scholar 

  • Koerner SE, Collins SL. 2014. Interactive effects of grazing, drought, and fire on grassland plant communities in North America and South Africa. Ecology 95:98–109.

    PubMed  Google Scholar 

  • Macandza VA, Owen-Smith N, Cross PC. 2004. Forage selection by African buffalo in the late dry season in two landscapes. S Afr J Wildl Res 34:113–21.

    Google Scholar 

  • Mc Naughton SJ. 1979. Grazing as an optimization process: grass-ungulate relationships in the Serengeti. Am Nat 113:691–703.

    Google Scholar 

  • Mc Naughton SJ. 1984. Grazing lawns: animals in herds, plant form, and coevolution. Am Nat 124:863–86. http://www.jstor.org/stable/2461305. Accessed 14 Apr 2011.

  • Mc Naughton SJ. 1985. Ecology of a grazing ecosystem: the Serengeti. Ecol Monogr 55:259–94. http://www.jstor.org/stable/1942578. Accessed 19 Jan 2011.

  • Mc Naughton SJ. 1990. Mineral nutrition and seasonal movements of African migratory ungulates. Nature 345:613–15.

    CAS  Google Scholar 

  • Mc Naughton SJ, Banyikwa FF, Mc Naughton MM. 1997. Promotion of the cycling of diet-enhancing nutrients by African grazers. Science (80-) 278:1798–800.

    CAS  Google Scholar 

  • Mc Naughton SJ, Milchunas DG, Frank DA. 1996. How can net primary productivity be measured in grazing ecosystems? Ecology 77:974–7.

    Google Scholar 

  • Mucina L, Rutherford MC, Eds. 2006. The vegetation of South Africa, Lesotho and Swaziland. Pretoria: South African National Biodiversity Institute.

    Google Scholar 

  • O’Connor TG. 1991. Patch colonization in a savanna grassland. J Veg Sci 2:245–54.

    Google Scholar 

  • O’Connor TG. 1994. Composition and population responses of an African savanna grassland to rainfall and grazing. J Appl Ecol 31:155–71.

    Google Scholar 

  • O’Connor TG. 1995. Transformation of a savanna grassland by drought and grazing. Afr J Forage Sci 12:53–60.

    Google Scholar 

  • Owen-Smith N, Ogutu JO. 2013. Controls over reproductive phenology among ungulates: allometry and tropical-temperate contrasts. Ecography (Cop) 36:256–63.

    Google Scholar 

  • Owen-Smith N, Traill LW. 2017. Space use patterns of a large mammalian herbivore distinguished by activity state: fear versus food? J Zool 303:281–90.

    Google Scholar 

  • van der Plas F, Zeinstra P, Veldhuis M, Fokkema R, Howison R, Olff H. 2013. Responses of savanna lawn and bunch grasses to water limitation. Plant Ecol 214:1157–68.

    Google Scholar 

  • R Development Core Team. 2016. R: A language and environment for statistical computing, reference index. Version 3.3.1. Vienna, Austria: R Foundation for Statistical Computing. Retrieved from http://ww-w.R-project.org.

  • Ratnam JV, Behera SK, Masumoto Y, Yamagata T. 2014. Remote effects of El Nino and Modoki events on the austral summer precipitation of southern Africa. Am Meteorol Soc 27:3802–16.

    Google Scholar 

  • Ribeiro PJ, Diggle PJ. 2016. Package ‘geoR’.

  • Sensenig RL, Demment MW, Laca EA. 2010. Allometric scaling predicts preferences for burned patches in a guild of East African grazers. Ecology 91:2898–907.

    PubMed  Google Scholar 

  • Simpson KJ, Ripley BS, Christin PA, Belcher CM, Lehmann CER, Thomas GH, Osborne CP. 2016. Determinants of flammability in savanna grass species. J Ecol 104:138–48.

    PubMed  Google Scholar 

  • Singh RS. 1993. Effect of winter fire on primary productivity and nutrient concentration of a dry tropical savanna. Vegetatio 106:63–71.

    Google Scholar 

  • Smith MD. 2011. An ecological perspective on extreme climatic events: a synthetic definition and framework to guide future research. J Ecol 99:656–63.

    Google Scholar 

  • Tainton NM. 1999. Veld management in South Africa. Pietermaritzberg: Natal University Press.

    Google Scholar 

  • Tomor BM, Owen-Smith N. 2002. Comparative use of grass regrowth following burns by four ungulate species in the Nylsvley Nature Reserve, South Africa. Afr J Ecol 40:201–4.

    Google Scholar 

  • Venter FJ, Scholes RJ, Eckhardt HC. 2003. The abiotic template and its associated vegetation pattern. In: Du Toit JT, Rogers KH, Biggs HC, Eds. The Kruger experience: ecology and management of savanna heterogeneity. Washington: Island Press. p 83–129.

    Google Scholar 

  • Waldram MS, Bond WJ, Stock WD. 2008. Ecological engineering by a mega-grazer: white rhino impacts on a South African savanna. Ecosystems 11:101–12.

    Google Scholar 

  • Walker BH, Emslie RH, Owen-Smith N, Scholes RJ. 1987. To cull or not to cull: lessons from a Southern African drought. J Appl Ecol 24:381–401.

    Google Scholar 

  • Whyte IJ, Joubert SCJ. 1988. Blue wildebeest population trends in the Kruger National Park and the effects of fencing. S Afr J Wildl Res 18:78–87.

    Google Scholar 

  • Yahdjian L, Sala OE. 2006. Vegetation structure constrains primary production response to water availability in the Patagonian steppe. Ecology 87:952–62.

    PubMed  Google Scholar 

  • Yoganand K, Owen-Smith N. 2014. Restricted habitat use by an African savanna herbivore through the seasonal cycle: key resources concept expanded. Ecography (Cop) 37:969–82.

    Google Scholar 

  • Zuur AF, Ieno EN, Walker NJ, Saveliev AA, Smith GM. 2009. Mixed effects models and extensions in ecology with R. New York: Springer.

    Google Scholar 

Download references

Acknowledgements

We thank Khensani Mkhonto for collecting data in the field. We are grateful to SANParks and Working on Fire for their continued support, particularly Navashni Govender and Tercia Strydom. This work was funded by the USAID/NAS program “Partnerships for Enhanced Engagement in Research” (Sub-Grant 2000004946, Cycle 3) and the Andrew Mellon Foundation. JED was funded by the National Research Foundation Freestanding, Innovation and Scarce Skills Development Fund (Grant No. 94250).

Author information

Author notes

  1. JED conceived and designed the study, performed the research, analysed the data and wrote the paper. CLP conceived and designed the study and wrote the paper. EHM conceived and designed the study and performed the research. SA conceived and designed the study, analysed the data and wrote the paper.

Authors and Affiliations

  1. School of Animal Plant and Environmental Sciences, University of the Witwatersrand, Private Bag 3, Wits, 2050, South Africa

    Jason Ernest Donaldson, Catherine L. Parr & Sally Archibald

  2. Department of Biology, Wake Forest University, 049 Winston Hall, Winston-Salem, North Carolina, 27109, USA

    Jason Ernest Donaldson

  3. School of Environmental Sciences, University of Liverpool, Liverpool, L69 3GP, UK

    Catherine L. Parr

  4. Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002, South Africa

    Catherine L. Parr

  5. Scientific Services, Kruger National Park, Private Bag X402, Skukuza, 1350, South Africa

    E. Happy Mangena

Authors
  1. Jason Ernest Donaldson
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Catherine L. Parr
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. E. Happy Mangena
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Sally Archibald
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Jason Ernest Donaldson.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary material 1 (DOCX 268 kb)

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Donaldson, J.E., Parr, C.L., Mangena, E.H. et al. Droughts Decouple African Savanna Grazers from Their Preferred Forage with Consequences for Grassland Productivity. Ecosystems 23, 689–701 (2020). https://doi.org/10.1007/s10021-019-00438-x

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s10021-019-00438-x

Keywords

Search

Navigation