Spatial cluster analysis for large herbivore distributions: Amboseli ecosystem, Kenya
Introduction
African savannah ecosystems are characterized by extensive seasonal migrations of large herbivores (Sinclair et al., 2007). In recent decades, rapid human population and land use changes have caused a loss of populations and range among most large herbivores (Ogutu et al., 2011). Amboseli ecosystem in southern Kenya, which has been continuously studied since the 1960s, provides a rich dataset showing the impact of human activity on a savannah ecosystem and wildlife populations (Western and Nightingale, 2003). Despite the abundant documentation of population and habitat changes, little has been published on the spatial changes in wildlife movements and species richness patterns (Mose et al., 2013).
In this paper we present an assessment of species distributions and spatial utilization of selected species using spatial hierarchical cluster analysis of large herbivore populations from the 1970s to 2000s. The species include buffalo (BF), elephant (EL), Grant's gazelles (GG) Thomson's gazelles (TG), wildebeest (WL) and zebra (ZB). The analysis covers a range of body size to explore long term changes in spatial distribution and richness, the primary agents and the differential effects on species. We use spatial cluster analysis as a tool for detecting data patterns, the changes in pattern over time and the conservation implications.
Section snippets
Study area and methods
The 8500 km2 (Fig. 1) Amboseli ecosystem straddling the Kenya–Tanzania border is defined by the seasonal movements of large herbivores and includes the 388 km2 Amboseli National Park. Further details of the ecosystem are provided elsewhere (Western, 2006). Land subdivision, settlement, agriculture and loss of seasonal grazing (Okello, 2005) have led to range restriction and fragmentation of pastoral livestock and wildlife populations over the last four decades (Western, 2006, Worden, 2007).
In
Results
Species clustered into four groups in both the 1970s and 2000s. In the 1970s, species richness was relatively uniform within and across clusters (Fig. 3). Each of the six species fell into any of the four clusters identified fairly randomly. Clusters 1, 2, and 3 recorded the maximum species richness (Fig. 3). Cluster 4 had a species richness of 5. By the 2000s only cluster 2 had maximum species richness, indicating a compression of species into and around the national park (Fig. 2). Cluster 4
Discussion
In the 1970s species were widespread across the ecosystem, but by the 2000s showed a heavy contraction of range and concentration in the vicinity of Amboseli National Park (Fig. 2). The major causes of compression are an expansion of the agricultural areas (Fig. 5), draining of the swamps east of the national park for irrigation, increase in human settlement (Fig. 4), land subdivision and sedentarization (Western and Nightingale, 2003), leading to loss of rangeland productivity (Groom and
Acknowledgments
We wish to thank the many wardens and the staff of Kenya Wildlife Service for their support over the years, David Maitumo for being part of the data collection team and Lucy Waruingi for logistical support. Liz Claiborne Ortenberg Foundation: www.lcaof.org (Grant Number: LCAOF-ACP2014) funded the data collection.
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