Surface-water constraints on herbivore foraging in the Kruger National Park, South Africa
Surface-water constraints on herbivore foraging in the Kruger National Park, South Africa
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DOI：
10.1890/01-0625
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发表时间：
2003-08-01
期刊：
影响因子：
4.8
通讯作者：
Getz, WM
中科院分区：
文献类型：
--
作者：
Redfern, JV;Grant, R;Getz, WM
在景观尺度上，生物和非生物因素的综合影响可能决定了非洲稀树草原生态系统中大型食草动物的分布格局。在这些生态系统中觅食的食草动物可能会成为营养压力在每年的旱季时，饲料的质量和数量都减少。此外，水源的位置可能会对旱季食草动物的分布施加限制。我们使用逻辑回归分析了13年来在南非克鲁格国家公园（KNP）收集的航空普查数据，并评估了关于地表水、饲料质量和饲料数量对8种食草动物旱季、大规模分布模式的相对影响的假设，利用以前对物种相对水分依赖性的观察，提出了关于物种分布与距水距离之间相关程度的假设。我们还开发了假设物种之间的权衡，可能会发生地表水的限制和营养需求时，无论是饲料质量或数量减少的反应。总的来说，我们预计物种与水的平均距离会增加，这是由于个体减轻了营养需求的限制（即，水的质量或数量）。我们的分析表明，营养需求和地表水的限制，物种王牌之间的权衡根据物种的水依赖，大小和肠道形态。在我们分析的四种食草动物中，水羚。分布似乎主要受到地表水供应的限制。布法罗是一种大型反刍食草动物，其分布表明，当饲料量减少时，个体面临营养需求和地表水限制之间的权衡。或者，角马（一种较小的反刍食草动物）的分布表明，当获得高质量饲料的机会有限时，个体会面临这种“权衡”。与布法罗和角马相比，当饲料质量或数量减少时，斑马（一种大小与角马相似的非反刍动物）的这种权衡的强度是中等的。浏览器的分布模式的特点是一个弱的关系与距离水，预期这些相对水独立的物种。相对于饲料质量的人口密度混淆探索这种权衡混合饲养。
At a landscape scale, the combined influence of biotic and abiotic factors may determine the distribution patterns of large herbivores in African savanna ecosystems. Herbivores foraging in these ecosystems may become nutritionally stressed during an annual dry season when both forage quality and quantity are reduced. Additionally, the locations of water sources may impose a landscape-scale constraint on dry-season herbivore distributions. We used logistic regression to analyze 13 years of aerial census data collected in the Kruger National Park (KNP), South Africa, and evaluated hypotheses regarding the relative influences that surface water, forage quality, and forage quantity exert on the dry-season, landscape-scale distribution patterns of eight herbivore species, Hypotheses regarding the degree of correlation between species' distributions and distance to water were developed using previous observations of species' relative water dependence. We also developed hypotheses regarding species' responses to the trade-off that may occur between surface-water constraints and nutritional requirements when either forage quality or quantity is reduced. In general, we expect an increase in species' mean distance to water as a result of individuals mitigating limitations in nutritional requirements (i.e., intake quality or quantity) by foraging farther from water. Our analyses, suggest that the trade-off between nutritional requirements and surface-water constraints that species ace varies according to the species' water dependence, size, and gut morphology. Of the four grazers considered in our analyses, waterbuck. distributions appear to be constrained primarily by surface-water availability. Distributions of buffalo, a large ruminant grazer, suggest that individuals face a trade-off between nutritional requirements and surface-water constraints when forage quantity is reduced.. Alternatively, distributions of wildebeest, a-smaller ruminant grazer, suggest that individuals face this' trade-off when access-to high-quality forage is limited. In comparison to buffalo and, wildebeest, the strength of this trade-off is moderate for zebra, a nonruminant similar in size to wildebeest, when either forage quality or quantity is reduced. Distribution patterns for browsers are characterized by a weak relationship with distance to Water, as expected for these relatively water-independent species. Population densities relative to forage quality confound exploration of this trade-off for mixed feeders.