Estación Experimental de Zonas Áridas (EEZA-CSIC), Ctra. de Sacramento s/n, La Cañada de San Urbano, Almería, Spain.
PLoS One. 2013 Jul 10;8(7):e68862. doi: 10.1371/journal.pone.0068862. Print 2013.
Chemical defences against predators are widespread in the animal kingdom although have been seldom reported in birds. Here, we investigate the possibility that the orange liquid that nestlings of an insectivorous bird, the Eurasian roller (Coracias garrulus), expel when scared at their nests acts as a chemical defence against predators. We studied the diet of nestling rollers and vomit origin, its chemical composition and deterrent effect on a mammal generalist predator. We also hypothesized that nestling rollers, as their main prey (i.e. grasshoppers) do from plants, could sequester chemicals from their prey for their use. Grasshoppers, that also regurgitate when facing to a threat, store the harmful substances used by plants to defend themselves against herbivores. We found that nestling rollers only vomit after being grasped and moved. The production of vomit depended on food consumption and the vomit contained two deterrent chemicals (hydroxycinnamic and hydroxybenzoic acids) stored by grasshoppers and used by plants to diminish herbivory, suggesting that they originate from the rollers' prey. Finally, we showed for the first time that the oral secretion of a vertebrate had a deterrent effect on a model predator because vomit of nestling rollers made meat distasteful to dogs. These results support the idea that the vomit of nestling rollers is a chemical defence against predators.
动物界广泛存在防御捕食者的化学物质，尽管鸟类中的此类物质鲜有报道。在这里，我们研究了一种可能性，即食虫鸟欧亚红隼（Coracias garrulus）雏鸟在巢穴中受到惊吓时排出的橙色液体是否具有防御捕食者的化学作用。我们研究了雏隼的饮食和呕吐物的来源、其化学成分，以及对一种哺乳动物捕食者的驱避作用。我们还假设，雏隼会像它们的主要猎物（即蝗虫）从植物中那样，从猎物那里摄取化学物质并将其用于自身防御。蝗虫在面对威胁时也会反刍，它们会储存植物用于防御草食动物的有害物质。我们发现，雏隼只有在被抓住和移动时才会呕吐。呕吐的产生取决于食物的摄入，并且呕吐物中含有两种驱避化学物质（羟基肉桂酸和羟基苯甲酸），这些化学物质是由蝗虫储存的，植物也会利用这些化学物质来减少草食性，这表明它们来自于雏隼的猎物。最后，我们首次表明，脊椎动物的口腔分泌物对模型捕食者具有驱避作用，因为雏隼的呕吐物使肉对狗变得不可口。这些结果支持了这样一种观点，即雏隼的呕吐物是一种防御捕食者的化学物质。
