KLEE: the Kenya Long-term Exclosure Experiment

1. Figure 3. Density of rodents in the presence or absence of large herbivores. Plots without large herbivores have about twice as many mice, even through pronounced fluctuations in abundance. KLEE: the Kenya Long-term Exclosure Experiment Truman Young, Frederick Erii, Kari Veblen, Corinna Riginos, Felicia Keesing Livestock and wildlife share much of their range in African savannas. To understand the interactions between livestock and wild herbivores (and other indigenous biodiversity), we have established a long-term herbivore exclusion experiment in the Laikipia ecosystem. Using different kinds of barriers, we differentially exclude various combinations of cattle, large wild herbivores, and ‘mega-herbivores’ (giraffes and elephants) from 18 four-hectare plots (Figure 1). Established in 1995, this project is the first controlled, replicated exclusion of different combinations of rangeland herbivores. We are monitoring soils, trees, herb layer vegetation, plant defense, grass productivity, use by large mammals, and populations of rodents, birds, & invertebrates. We report here 1) evidence of competition between cattle and wildlife, 2) evidence that elephants may mitigate the competition between cattle and zebras, and 3) an examination of the fate of a savanna when all large herbivores have been removed. The pathology of no herbivory African savannas have coexisted and co-evolved with large herbivores for millions of years, and with livestock for millennia. The total exclusion treatment in the KLEE plots at first developed rank grass cover and thick thatch. This was followed by a severe drought (in an “La Nina” year), during which there was severe reduction of living and dead biomass, and the death of larger grass plants suppressed by rankness (Figure 5). Large numbers of herbs appeared in the bare areas among the remnant grasses. In subsequent years, large areas of the exclusion plots converted to a herb-dominated community, with reduced grass cover (Figure 6). We attribute these “pathological” changes in the total exclusion plots to the novel conditions for which some of its dominant species were ill-adapted. In the last couple of years, it appears that the grasses may be slowly returning to dominance on the total exclusion plots. Figure 5. After being suppressed by rank growth, larger grass plants died during the 2000/1 drought in plots without herbivores, but not in the plots grazing by native herbivores and livestock. Do elephants sometimes mitigate the competition between cattle and zebras? Notice in Figure 4 that the presence of elephants reduced both grass and zebra use when there were no cattle (because they all eat grass), but increased grass and zebras in the presence of cattle. It appears that elephants removed key forage plants (Commelina), causing cattle to eat less (and remove less grass). In other words, in the presence of cattle, elephants facilitate (increase) zebras. This was a completely unexpected result. Competition among herbivores Many species share the grasses and herbs of the Laikipia savannas, but the only way to know if they are competing is to remove certain herbivores, and see whether others increase. The KLEE experiment now has evidence that there is competition among most, but not all, of these rangeland herbivores: 1. Removing cattle increases Grant’s gazelles, hartebeest, eland, elephant and zebra (Figs 2 & 4). Removing wildlife (zebras, mostly), increases rangeland savanna use by elephants, and increases forage intake rates of cattle. Removing large herbivores doubles the numbers of mice (Figure 3). We estimate that half of the grass you would expect to be available to cattle (or zebras) after the removal of zebras (or cattle) is instead being eaten by increased numbers of mice. In contrast, grasshoppers do not increase, regardless of which other grass eaters we exclude. We suspect that this is because the number of grasshoppers is determined more by their predators than by their food. Figure 6. After the death of grasses in the drought, herbs came to dominate large areas of the exclusion plots, where they continue to cover twice the ground as in the control plots. Figure 2. Excluding cattle increases wildlife use Elephants (M) reduce grass and zebra use when cattle are absent Elephants increase grass and zebra use when cattle are present Percent cover Outreach In addition to writing “KLEE Corner” for the LWF Newsletter, we have published over 30 scientific articles from this research project (list available ) La Nina drought El Nino rains Figure 4. In plots with cattle, there is less grass and fewer zebras than in plots without cattle. Data from Felicia Keesing Acknowledgements: The exclosure plots were built and have been maintained by grants from the James Smithson Fund of the Smithsonian Institution (to Alan P. Smith), The National Geographic Society, The National Science Foundation, and the African Elephant Program of the U.S. Fish and Wildlife Service (to T.P. Young). We also appreciate the generosity of the late George Small and the support of Nick Georgiadis and John and Ken Wreford Smith. The plots are currently maintained by the KLEE field crew: Fred Erii, John Lochukuya, Jackson Ekadeli, Patrick Etelej, Kari Veblen, Corinna Riginos, and Dan Kelly. Doctoral and Masters students supported by KLEE: Bell Okello, Ph.D. Candidate, University of Natal David Kinyua, no degree, University of Nairobi Michelle Gadd, Ph.D., University of California Todd Palmer, Ph.D., University of California Wilfred Odadi, M.Sc. Moi Univ.; and Ph.D. candidate, Egerton Silvanos Otieno, M.Sc., University of Nairobi Charles Warui, Ph.D., Rhodes University Ryan Sensenig, Ph.D. candidate, University of California Kari Veblen, Ph.D. candidate, University of California Isaac Kimathi, M.Sc., University of Nairobi Corinna Riginos, Ph.D. candidate, University of California Lucy Ngatia, M.Sc. candidate, University of Nairobi