Parrots Eat Nutritious Foods despite Toxins
Parrots Eat Nutritious Foods despite Toxins
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DOI：
10.1371/journal.pone.0038293
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发表时间：
2012-06-05
期刊：
影响因子：
3.7
通讯作者：
Toft, Catherine A.
中科院分区：
文献类型：
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作者：
Gilardi, James D.;Toft, Catherine A.
背景：多面手食草动物不仅面临植物性食物低氮和高消化率的挑战，而且还面临植物的物理和化学防御。这项研究调查了秘鲁亚马逊地区野生鹦鹉的食物，并询问这些食物是否含有限制一般食草动物的饮食成分（蛋白质、脂质、矿物质），以及含量是多少；鹦鹉是否根据营养成分选择食物；以及鹦鹉是否会避开有化学防御的植物。研究方法/主要发现：在2个旱季（1992-1993年7 - 8月）和1个雨季（1994年1 - 2月），对未受干扰的热带雨林中8属17种散养鹦鹉在102种树木上觅食进行了224次野外观察。我们对鹦鹉吃和不吃的植物部分进行了实验室分析，并对卤水虾进行了毒性测试，作为脊椎动物的代理。鹦鹉吃种子、水果、花、树叶、树皮和昆虫幼虫，但它们的食物中有70%是由许多热带树木的种子组成的，这些种子处于不同的成熟阶段。鹦鹉吃的植物部分富含蛋白质、脂肪和必需的矿物质，以及潜在的有毒化学物质。种子的蛋白质和脂肪含量高于其他植物材料，纤维含量低于其他植物材料。三种大型金刚鹦鹉所吃的食物中蛋白质和脂肪含量较高，而纤维含量较低，与可获得但不吃的植物部分相比。金刚鹦鹉吃的食物中酚类化合物的含量低于它们不吃的食物。然而，金刚鹦鹉所吃的食物含有可测量的毒性。金刚鹦鹉似乎不会根据矿物质含量来选择饮食。结论/意义：鹦鹉是一种多面手食草动物，尽管植物有化学防御，但它们仍会破坏性地消耗种子。有了吃有毒食物的能力，生活在雨林中的鹦鹉利用了多种营养食物，即使是在其他食果动物和花岗岩动物食物匮乏的旱季。
Background: Generalist herbivores are challenged not only by the low nitrogen and high indigestibility of their plant foods, but also by physical and chemical defenses of plants. This study investigated the foods of wild parrots in the Peruvian Amazon and asked whether these foods contain dietary components that are limiting for generalist herbivores (protein, lipids, minerals) and in what quantity; whether parrots chose foods based on nutrient content; and whether parrots avoid plants that are chemically defended.Methodology/Principal Findings: We made 224 field observations of free-ranging parrots of 17 species in 8 genera foraging on 102 species of trees in an undisturbed tropical rainforest, in two dry seasons (July-August 1992-1993) and one wet season (January-February 1994). We performed laboratory analyses of parts of plants eaten and not eaten by parrots and brine shrimp assays of toxicity as a proxy for vertebrates. Parrots ate seeds, fruits, flowers, leaves, bark, and insect larvae, but up to 70% of their diet comprised seeds of many species of tropical trees, in various stages of ripeness. Plant parts eaten by parrots were rich in protein, lipid, and essential minerals, as well as potentially toxic chemicals. Seeds were higher than other plant materials in protein and lipid and lower in fiber. Large macaws of three species ate foods higher in protein and lipids and lower in fiber compared to plant parts available but not eaten. Macaws ate foods that were lower in phenolic compounds than foods they avoided. Nevertheless, foods eaten by macaws contained measurable levels of toxicity. Macaws did not appear to make dietary selections based on mineral content.Conclusions/Significance: Parrots represent a remarkable example of a generalist herbivore that consumes seeds destructively despite plant chemical defenses. With the ability to eat toxic foods, rainforest-dwelling parrots exploited a diversity of nutritious foods, even in the dry season when food was scarce for other frugivores and granivores.