Abraham Joel O, Hempson Gareth P, Staver A Carla
Department of Ecology and Evolutionary Biology Yale University New Haven Connecticut.
South African Environmental Observation Network (SAEON), Ndlovu Node Pretoria South Africa.
Ecol Evol. 2019 May 22;9(12):7047-7056. doi: 10.1002/ece3.5270. eCollection 2019 Jun.
Climate models predict increases in drought frequency and severity worldwide, with potential impacts on diverse systems, including African savannas. These droughts pose a concern for the conservation of savanna mammal communities, such that understanding how different species respond to drought is vital.Because grass decreases so consistently during droughts, we predict that grass-dependent species (grazers and mixed feeders) will respond strongly to drought, whether by changing diets, seeking drought refugia, or suffering mortality.A recent severe but heterogeneous drought in Kruger National Park, South Africa, afforded a rare opportunity to test these hypotheses in situ-crucial, given the central role of landscape-scale movement as a potential herbivore strategy. We used herbivore dung as a proxy, integrating spatial distributions (dung counts) with diet composition (carbon isotope analysis of dung).As predicted, browsers showed little response to drought. However, mixed feeders switched their diets to incorporate more C3 trees/forbs, but did not move. Meanwhile, grazers and megaherbivores instead moved toward drought refugia. : The responses we observed by savanna herbivores are largely amplifications of typical dry season strategies and reflect constraints imposed by body size and feeding ecology. Grazers may be at particular risk from increased drought frequency and spatial extent if drought refugia become decreasingly available. Conservation strategies should recognize these constraints and work to facilitate the diverse responses of herbivores to drought.
气候模型预测，全球干旱的频率和严重程度将会增加，这可能会对包括非洲稀树草原在内的各种系统产生影响。这些干旱引发了对稀树草原哺乳动物群落保护的担忧，因此了解不同物种如何应对干旱至关重要。由于干旱期间草的数量持续减少，我们预测依赖草的物种（食草动物和混合食性动物）将对干旱做出强烈反应，无论是通过改变饮食、寻找干旱避难所还是面临死亡。南非克鲁格国家公园最近发生了一次严重但分布不均的干旱，这提供了一个在实地检验这些假设的难得机会——鉴于景观尺度的迁移作为一种潜在的食草动物策略所起的核心作用，这一点至关重要。我们以食草动物的粪便为替代物，将空间分布（粪便计数）与饮食组成（粪便的碳同位素分析）结合起来。正如预测的那样，食叶动物对干旱几乎没有反应。然而，混合食性动物改变了它们的饮食，纳入了更多的C3树木/草本植物，但没有迁移。与此同时，食草动物和大型食草动物则向干旱避难所迁移。我们观察到的稀树草原食草动物的反应在很大程度上是对典型旱季策略的放大，反映了体型和觅食生态所带来的限制。如果干旱避难所越来越少，食草动物可能会因干旱频率增加和空间范围扩大而面临特别的风险。保护策略应认识到这些限制，并努力促进食草动物对干旱的多样化反应。
