Landscape-scale analyses suggest both nutrient and antipredator advantages to Serengeti herbivore hotspots

T. Michael Anderson, J. Grant C. Hopcraft, Eby Stephanie, Mark Ritchie, James B. Grace, Han Olff

Research output: Contribution to journalArticlepeer-review

80 Scopus citations

Abstract

Mechanistic explanations of herbivore spatial distribution have focused largely on either resource-related (bottom-up) or predation-related (top-down) factors. We studied direct and indirect influences on the spatial distributions of Serengeti herbivore hotspots, defined as temporally stable areas inhabited by mixed herds of resident grazers. Remote sensing and variation in landscape features were first used to create a map of the spatial distribution of hotspots, which was tested for accuracy against an independent data set of herbivore observations. Subsequently, we applied structural equation modeling to data on soil fertility and plant quality and quantity across a range of sites. We found that hotspots in Serengeti occur in areas that are relatively flat and located away from rivers, sites where ungulates are less susceptible to predation. Further, hotspots tend to occur in areas where hydrology and rainfall create conditions of relatively low-standing plant biomass, which, coupled with grazing, increases forage quality while decreasing predation risk. Low-standing biomass and higher leaf concentrations of N, Na, and Mg were strong direct predictors of hotspot occurrence. Soil fertility had indirect effects on hotspot occurrence by promoting leaf Na and Mg. The results indicate that landscape features contribute in direct and indirect ways to influence the spatial distribution of hotspots and that the best models incorporated both resource- and predation-related factors. Our study highlights the collective and simultaneous role of bottom-up and top-down factors in determining ungulate spatial distributions.

Original languageEnglish (US)
Pages (from-to)1519-1529
Number of pages11
JournalEcology
Volume91
Issue number5
DOIs
StatePublished - May 2010

Keywords

  • Forage quantity vs. Quality
  • Grazing lawns
  • Herbivore habitat selection
  • Near-infrared difference vegetation index (ndvi)
  • Predator-prey
  • Remote sensing
  • Serengeti
  • Soil nutrients
  • Structural equation modeling
  • Topographic relief
  • Ungulate spatial distribution

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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