Papi F, Luschi P, Akesson S, Capogrossi S, Hays G C
Dipartimento di Etologia, Ecologia, Evoluzione, University of Pisa, Via A. Volta 6, I-56126 Pisa, Italy.
J Exp Biol. 2000 Nov;203(Pt 22):3435-43. doi: 10.1242/jeb.203.22.3435.
Green turtles (Chelonia mydas) that shuttle between their Brazilian feeding grounds and nesting beaches at Ascension Island in the middle of the Atlantic Ocean are a paradigmatic case of long-distance oceanic migrants. It has been suggested that they calculate their position and the direction of their target areas by using the inclination and intensity of the earth's magnetic field. To test this hypothesis, we tracked, by satellite, green turtles during their postnesting migration from Ascension Island to the Brazilian coast more than 2000 km away. Seven turtles were each fitted with six powerful static magnets attached in such a way as to produce variable artificial fields around the turtle that made reliance on a geomagnetic map impossible. The reconstructed courses were very similar to those of eight turtles without magnets that were tracked over the same period and in the previous year, and no differences between magnetically disrupted and untreated turtles were found as regards navigational performance and course straightness. These findings show that magnetic cues are not essential to turtles making the return trip to the Brazilian coast. The navigational mechanisms used by these turtles remain enigmatic.
绿海龟（蠵龟）穿梭于巴西的觅食地和位于大西洋中部阿森松岛的筑巢海滩之间，是远距离海洋迁徙动物的典型例子。有人提出，它们通过利用地球磁场的倾斜度和强度来计算自己的位置以及目标区域的方向。为了验证这一假设，我们通过卫星追踪了绿海龟在筑巢后从阿森松岛迁徙到2000多公里外的巴西海岸的过程。七只绿海龟每只都被安装了六块强力静态磁铁，安装方式使得海龟周围产生可变的人工磁场，从而无法依靠地磁图。重建的路线与同期以及前一年追踪的八只未安装磁铁的海龟的路线非常相似，在导航性能和路线直线度方面，未发现受磁场干扰的海龟和未处理海龟之间存在差异。这些发现表明，磁信号对于海龟返回巴西海岸的旅程并非必不可少。这些海龟所使用的导航机制仍然是个谜。
