Iwata Yuji, Nakashima Yoshihiro, Tsuchida Sayaka, Nguema Pierre Philippe Mbehang, Ando Chieko, Ushida Kazunari, Yamagiwa Juichi
Kyoto University, Graduate School of Science, Kitashirakawa, Kyoto 606-8502, Japan.
J Vet Med Sci. 2015 Oct;77(10):1247-52. doi: 10.1292/jvms.15-0111. Epub 2015 May 21.
African rainforest harbors herbivores at high density. However, because plants and soils typically lack in some essential minerals, rainforest is not always a suitable habitat for herbivores. How they fulfill the mineral requirements is therefore an important question to animal ecology and conservation. Although large marshes, called 'bais', are often mentioned as efficient mineral-resource, little information on other sodium resources has still been available. Our laboratory works and field surveys found that a peculiar item, decaying wood stumps of Anthostema aubryanum, played as a major sodium resource for herbivores in Moukalaba-Doudou National Park, Gabon. When A. aubryanum is alive, the sodium content of its bark is low and its latex is toxic. Sodium is accumulated in decaying stumps (mean=1,343 mg/kg dry matter). Eight herbivores visited stumps to ingest the dead wood. Fecal sample analysis revealed that western lowland gorillas, a species most-frequently using the stumps, consumed large amount of the dead wood as regular food. Our findings suggest that decaying A. aubryanum is critical sodium-resources and is a key species for herbivores in our study area. Importance of the A. aubryanum may be particularly large there, because it is a limited sodium-rich material that is available year round. Our study site is known as the site where the densities of several herbivores are among the highest at Central Africa. The relatively high herbivores density in our study site may partly depend on decaying A. aubryanum as sodium resources.
非洲雨林中食草动物密度很高。然而，由于植物和土壤通常缺乏某些必需矿物质，雨林并不总是适合食草动物生存的栖息地。因此，它们如何满足矿物质需求是动物生态学和保护领域的一个重要问题。尽管被称为“bais”的大型沼泽地常被提及是有效的矿物质资源，但关于其他钠资源的信息仍然很少。我们实验室的研究工作和实地调查发现，一种奇特的东西，即奥氏花萼木腐烂的树桩，是加蓬穆卡拉巴 - 杜杜国家公园食草动物的主要钠资源。当奥氏花萼木活着的时候，它树皮中的钠含量很低，其乳胶有毒。钠会在腐烂的树桩中积累（平均干物质含量为1343毫克/千克）。八种食草动物会到树桩处啃食枯木。粪便样本分析显示，西部低地大猩猩是最常使用这些树桩的物种，它们将大量枯木作为常规食物食用。我们的研究结果表明，腐烂的奥氏花萼木是关键的钠资源，是我们研究区域食草动物的关键物种。奥氏花萼木的重要性在那里可能特别大，因为它是一种全年都可获取的有限的富钠物质。我们的研究地点是中非地区几种食草动物密度最高的地点之一。我们研究地点相对较高的食草动物密度可能部分取决于腐烂的奥氏花萼木作为钠资源。
