Renewal: Geomagnetic Maps and Magnetic Navigation in Sea Turtles

海龟的远距离迁徙涉及到动物界中一些最非凡的定向和导航壮举。刚孵化的海龟第一次进入海洋时，会立即建立走向公海的航线，并在游泳到看不见陆地的很长时间后坚定不移地保持这些航线。随着海龟的成熟，它们通常会沿着跨越整个大洋盆地的复杂迁徙路线。年长的海龟在觅食地栖息，但经常长途迁徙到特定的交配和筑巢地点，之后许多海龟导航回到它们以前居住的相同觅食地点。海龟如何在看似平淡无奇的广阔海洋中引导自己，一直是动物行为的一个永恒的谜团。越来越多的证据表明，地球磁场为海龟提供了一个重要的方向和位置信息来源，这些信息可以在它们生命的不同时期以不同的方式使用。作为刚孵化出来的海龟，海龟可能会首先使用地球的磁场作为方向信号，使它们在迁徙到海洋时保持头部。后来，在开阔的海洋中，区域磁场显然起到了导航标志的作用，在关键的地理边界处引发了游泳方向的变化，从而帮助小海龟保持在有利的海洋区域，并沿着迁徙路线前进。然而，这个年龄的海龟不会导航到特定的地点。相比之下，年龄较大的幼龟在沿海觅食地栖息，最近的证据表明，它们获得了一张磁性地图？这使它们能够导航到特定的进食地点。类似的导航能力可以解释成年海龟是如何找到筑巢海滩的。这项拟议的研究旨在调查磁性线索在引导海龟迁徙中所起的作用。研究人员将调查在它们第一次跨洋迁徙过程中，年轻的黑头海豚是如何利用区域磁场作为公海航行标志的。此外，研究人员还将研究新发现的幼龟磁性地图感，以深入了解海龟如何利用磁场导航到特定的进食地点，并确定地图是如何组织的。更好地了解海龟在跨洋迁徙过程中如何引导自己，并学会寻找特定的地理位置，将有助于保护努力拯救这些濒临灭绝的物种。此外，这项工作的结果可能会为与人类导航相关的新方法提供见解。该项目将为一些本科生和研究生提供研究经验。

The long-distance migrations of sea turtles involve some of the most extraordinary feats of orientation and navigation in the animal kingdom. Hatchling turtles entering the ocean for the first time immediately establish courses toward the open sea and steadfastly maintain them long after swimming beyond sight of land. As the turtles mature, they often follow complex migratory pathways that span entire ocean basins. Older turtles take up residence in feeding grounds but regularly migrate long distances to particular mating and nesting sites, after which many navigate back to the same feeding sites that they inhabited previously. How sea turtles guide themselves across vast expanses of seemingly featureless ocean has remained an enduring mystery of animal behavior.Growing evidence suggests that the Earth's magnetic field provides turtles with an important source of both directional and positional information that can be used in different ways at different times in their lives. As hatchlings, turtles may first use the Earth's field as a directional cue that enables them to maintain headings as they migrate out to sea. Later, in the open ocean, regional magnetic fields apparently function as navigational markers that elicit changes in swimming direction at crucial geographic boundaries, thus helping young turtles remain within favorable oceanic regions and progress along the migratory route. Turtles of this age, however, do not navigate to specific locations. In contrast, older juvenile turtles take up residence in coastal feeding grounds, and recent evidence indicates that they acquire a ?magnetic map? that enables them to navigate to specific feeding sites. A similar navigational ability may explain how adult turtles locate nesting beaches.The proposed research is designed to investigate the role that magnetic cues play in guiding the migrations of sea turtles. The researchers will investigate how young loggerheads exploit regional magnetic fields as open-sea navigational markers during their first transoceanic migration. In addition, the researchers will study the newly discovered magnetic map sense of juvenile turtles to gain insight into how turtles use magnetic fields to navigate to specific feeding sites and to determine how the map is organized. An improved understanding of how sea turtles guide themselves during transoceanic migrations, and learn to find specific geographic locations, will benefit conservation efforts to save these jeopardized species from extinction. In addition, the results of the work may provide insights into new methodologies relevant to human navigation. The project will provide research experience for a number of undergraduate and graduate students.