Overwintering Requirements of the Monarch Butterfly in Mexico: Habitat Selection Versus Habitat Suitability

每年秋天，北美东部大部分地区多达10亿只帝王蝶向南迁移到墨西哥的山区。 数以千万计的它们聚集在几英亩的森林里。 这些高海拔地区几乎没有蝴蝶可以食用的花朵，因此蝴蝶必须保持寒冷，以减缓它们在迁徙过程中积累的能量储备（脂质）的消耗。 这些地点经常遭受严重的冬季风暴，而森林树冠层则起到了保护毯和保护伞的作用。 在这个项目中，耐寒性实验和脂质分析将对气候如何影响蝴蝶的生存和个体消耗能量储备的速度产生更强的影响。 详细研究蜂群内和附近未被蝴蝶选择的地点的小气候，将有助于解释为什么蝴蝶在栖息地的使用上如此有选择性。 勘探工作将利用空中侦察和卫星图像，在已确定具有适宜小气候的森林中寻找更多的越冬区。 地理信息系统（GIS）分析将整合所有这些组成部分，以确定目前的适宜生境范围，并将量化适宜生境在过去四十年中的变化。 人类正在通过伐木、火灾和生态旅游改变帝王蝶过冬的森林。帝王蝶独特的迁徙的长期持续性取决于适当的越冬场所的持续性。因此，这项研究对关注这一非凡野生动物奇观的科学家、政策制定者和公民具有保护意义。

Every autumn, up to a billion monarch butterflies across most of eastern North America migrate south to the mountains of Mexico. By the tens of millions they cluster in forests on a handful of acres. These high altitude sites have few flowers on which butterflies can feed, so the butterflies must stay cold to slow their expenditure of the energy reserves (lipids) they accumulated during their migration. The sites are subject to severe winter storms, and the forest canopy serves as a protective blanket and umbrella. In this project, cold tolerance experiments and lipid analyses will develop a stronger picture of how climate affects both butterfly survival and the rate at which individuals deplete their energy reserves. Detailed studies of microclimate within colonies and in nearby sites not selected by the butterflies will help explain why the butterflies are so selective in their habitat use. Using aerial reconnaissance and satellite imagery, exploration will search for additional overwintering areas in forests identified as having suitable microclimate. Geographic information system (GIS) analysis will integrate all of these components to determine the current extent of suitable habitat, and will quantify how suitable habitat has changed over the past forty years. Humans are altering the forests where the monarchs overwinter, through logging, fires and ecotourism. The longterm persistence of the monarchs' unique migration depends upon the persistence of appropriate wintering sites. This research has conservation implications, therefore, for scientists, policymakers and citizens concerned about this extraordinary wildlife spectacle.