Opposing Rainfall and Plant Nutritional Gradients Best Explain the Wildebeest Migration in the Serengeti
Opposing Rainfall and Plant Nutritional Gradients Best Explain the Wildebeest Migration in the Serengeti
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DOI：
10.1086/597229
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发表时间：
2009-04-01
影响因子：
2.9
通讯作者：
Fryxell, John M.
中科院分区：
文献类型：
--
作者：
Holdo, Ricardo M.;Holt, Robert D.;Fryxell, John M.
人们提出了多种假设来解释塞伦盖蒂角马的年度迁徙，但很少有研究将分布模式与环境驱动因素进行比较。我们使用了一个降雨驱动的草地动态和角马运动模型来模拟角马的月度分布，角马的运动决策取决于14个候选的适应运动模型，以响应资源的可用性。我们使用信息理论方法比较了3年来两个空间尺度上模拟和观测的月分布模式的拟合。在两个空间尺度上，包括绿草的摄取率和氮浓度以及树木覆盖对草生物量的抑制作用的模型都提供了最好的拟合，这表明消化限制和蛋白质需求可能在驱动迁移行为中起关键作用。据预测，迁徙的出现取决于角马在相对大范围（180-100公里）追踪资源丰度变化的能力。当迁徙决策仅仅基于当地资源的可用性时，角马就无法在整个生态系统中迁移。我们的研究强调了强烈的和抵消季节性驱动的降雨和生育力梯度的潜在关键作用——非洲稀树草原生态系统的一贯特征——作为有蹄类动物长距离季节性迁徙的驱动因素。
Multiple hypotheses have been proposed to explain the annual migration of the Serengeti wildebeest, but few studies have compared distribution patterns with environmental drivers. We used a rainfall-driven model of grass dynamics and wildebeest movement to generate simulated monthly wildebeest distributions, with wildebeest movement decisions depending on 14 candidate models of adaptive movement in response to resource availability. We used information-theoretic approaches to compare the fits of simulated and observed monthly distribution patterns at two spatial scales over a 3-year period. Models that included the intake rate and nitrogen (N) concentration of green grass and the suppressive effect of tree cover on grass biomass provided the best model fits at both spatial scales tested, suggesting that digestive constraints and protein requirements may play key roles in driving migratory behavior. The emergence of a migration was predicted to be dependent on the ability of the wildebeest to track changes in resource abundance at relatively large scales (180-100 km). When movement decisions are based solely on local resource availability, the wildebeest fail to migrate across the ecosystem. Our study highlights the potentially key role of strong and countervailing seasonally driven rainfall and fertility gradients-a consistent feature of African savanna ecosystems-as drivers of long-distance seasonal migrations in ungulates.