Department of Biology, Wake Forest University, Winston-Salem, NC 27109, USA.
Department of Statistical Sciences, Wake Forest University, Winston-Salem, NC 27109, USA.
Science. 2024 Feb 16;383(6684):782-788. doi: 10.1126/science.adg0744. Epub 2024 Feb 15.
Competition, facilitation, and predation offer alternative explanations for successional patterns of migratory herbivores. However, these interactions are difficult to measure, leaving uncertainty about the mechanisms underlying body-size-dependent grazing-and even whether succession occurs at all. We used data from an 8-year camera-trap survey, GPS-collared herbivores, and fecal DNA metabarcoding to analyze the timing, arrival order, and interactions among migratory grazers in Serengeti National Park. Temporal grazing succession is characterized by a "push-pull" dynamic: Competitive grazing nudges zebra ahead of co-migrating wildebeest, whereas grass consumption by these large-bodied migrants attracts trailing, small-bodied gazelle that benefit from facilitation. "Natural experiments" involving intense wildfires and rainfall respectively disrupted and strengthened these effects. Our results highlight a balance between facilitative and competitive forces in co-regulating large-scale ungulate migrations.
竞争、促进和捕食为迁徙食草动物的演替模式提供了替代解释。然而，这些相互作用很难衡量，这使得人们对体型依赖性放牧的机制以及演替是否真的发生存在不确定性。我们使用了来自 8 年的相机陷阱调查、GPS 项圈的食草动物和粪便 DNA 代谢组学的数据，来分析塞伦盖蒂国家公园中迁徙食草动物的时间、到达顺序和相互作用。时间上的放牧演替具有“推-拉”动态：竞争放牧促使斑马在共生的角马之前，而这些大型迁徙动物的草食性则吸引了尾随的、体型较小的瞪羚，它们从促进作用中受益。涉及强烈野火和降雨的“自然实验”分别干扰和加强了这些影响。我们的结果强调了促进和竞争力量之间的平衡，它们共同调节着大规模的有蹄类动物迁徙。
