Geomagnetic Position Fixing

摘要这项拟议的研究将调查脊椎动物利用地球磁场的倾角或倾角(定义为磁力线与重力之间的角度)的梯度来确定地理(地图)位置的能力。以前对寻的方向的研究表明，磁倾角可以用来推导出导航地图的一个坐标。为了更严格地测试磁倾角在提供地图信息方面的作用，将使用磁倾角的微小变化对寻的方向的影响来估计动物居所范围内的局部磁倾斜度的特征，例如倾斜度的“原始值”和梯度的对准。然后，这些从行为上得出的估计值将与通过绘制动物采集地点周围磁倾角的空间梯度图而获得的实际测量值进行比较。还将利用在南北和东西轴线上收集的动物相对于我们测试地点的反应进行比较，以帮助区分由于磁倾角变化而产生的“地图”和“非地图”效应，并确定是否使用真正的双坐标地图来确定地理位置。拟议的实验将有助于更好地理解磁场在寻的MAP组件中的作用。这些实验还将有助于确定生物系统对地磁场变化的敏感性下限，并在更一般的水平上确定脊椎动物神经系统测量物理刺激绝对值的精确度。

SummaryThe proposed research will investigate the ability of a vertebrate to use gradients in the inclination or 'dip angle' of the earth's magnetic field (defined as the angle between the magnetic field lines and gravity) to determine geographic ("map") position. Previous studies of homing orientation have shown that magnetic inclination may be used to derive one coordinate of a navigational map. To provide a more rigorous test of magnetic inclination's role in providing map information, the effects of small changes in magnetic inclination on homing orientation will be used to estimate characteristics of the local gradient of magnetic inclination within an animal's home range, e.g., the "home value" of inclination and the alignment of the gradient. These behaviorally derived estimates will then be compared with actual measured values obtained by mapping the spatial gradients of magnetic inclination around the sites where animals were collected. A comparison of the response of animals collected at sites along the north-south and east-west axes relative to our testing site will also be used to help distinguish "map" and "non-map" effects resulting from changes in magnetic inclination, and to determine whether a true bicoordinate map is being used to determine geographic position. The proposed experiments will contribute to a better understanding of the magnetic field's role in the map component of homing. These experiments will also help to determine the lower limits of the sensitivity of biological systems to variation in the geomagnetic field and, at a more general level, to determine the precision with which the vertebrate nervous system can measure the absolute values of physical stimuli.