Abstract Political boundaries may represent ecological barriers due to differences in wildlife management policies. In the European Union, it might be expected that these differences should be highly diluted, because all countries have to comply with common directives issued by the European Commission. However, the subsidiarity principle may lead to the uneven uptake of European Union regulations, which can impact on biodiversity conservation due to unequal legislation in neighboring countries, particularly in the case of highly mobile organisms. Here we address this issue, by analyzing how EU regulations issued in response to the Bovine Spongiform Encephalopathy (BSE) crisis differentially affected vulture conservation in Portugal and Spain. Taking advantage of the intensive GPS-tracking of 60 griffon (Gyps fulvus) and 11 cinereous vultures (Aegypius monachus) from Spain, we found that the Spanish-Portuguese border acts as a quasi-impermeable barrier. In fact, there was an abrupt decline in the number of vulture locations across the Spanish-Portuguese border, with modelling showing that this was unlikely to be related to differences in land cover or topography. Instead, the pattern found was likely due to differences in trophic resource availability, namely carcasses from extensive livestock husbandry, resulting from the differential application of European sanitary legislation regarding the mandatory removal of dead livestock from the field. Overall, our results should be seen as a warning signal to policy makers and conservation managers, highlighting the need for a stronger integration of sanitary and environmental policies at the European level.

中文翻译：

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无形的障碍：不同的卫生法规限制了秃鹰跨越国界的流动

摘要 由于野生动物管理政策的差异，政治边界可能代表生态障碍。在欧盟，这些差异应该被高度稀释，因为所有国家都必须遵守欧盟委员会发布的共同指令。然而，辅助性原则可能会导致欧盟法规的采用不均衡，这可能会由于邻国立法的不平等而影响生物多样性保护，特别是在高度流动的生物体的情况下。在这里，我们通过分析欧盟为应对牛海绵状脑病 (BSE) 危机而颁布的法规如何对葡萄牙和西班牙的秃鹰保护产生不同的影响来解决这个问题。利用对来自西班牙的 60 只狮鹫（Gyps fulvus）和 11 只灰秃鹫（Aegypius monachus）的密集 GPS 跟踪，我们发现西班牙-葡萄牙边境充当了准不透水屏障。事实上，跨越西班牙和葡萄牙边境的秃鹰地点数量突然下降，模型显示这不太可能与土地覆盖或地形的差异有关。相反，发现的模式可能是由于营养资源可用性的差异，即来自粗放畜牧业的尸体，这是由于欧洲卫生立法关于强制将死牲畜从田间移走的不同应用造成的。总的来说，我们的结果应该被视为对政策制定者和保护管理者的警告信号，