2010年10月22日
科學家們研究海龜遷徙靠什麼指引方向
開始一種結論是靠星星，可是海龜視力不好，很難看到，而且在烏雲密佈的晚上還是可以繼續遷徙（烏雲密佈這裏有道辭彙題）；然後還有一種是靠氣味，可是氣味不能維持很久，所以不適用於長途遷徙，而且在過程中有氣味干擾，但是海龜依然能找對方向；第三種是磁場，可是如果綁個磁鐵在領頭的海龜上，它還是可以辨別方向，所以也不是磁場。
但是有一個結論是海龜可能是用combine幾種方法，在靠近目的地時味道是有用的（有題）。最後一種解釋，是海龜體內的一種DNA，它能記錄海龜被孵化出的地點（也就是他們去的地方），並且由母海龜遺傳給小海龜。最後說有一個例子可以證明：從前在加勒比海的一個地方有很多綠海龜，但是後來捕殺很嚴重海龜們就不去了；近幾年雖然又保護起來了但是海龜們來得仍然很少。
How sea turtles navigation when they are migrate: First hypothesis is they can see the sun rise and sun sets; second hypothesis is they can feel the magnet (but it won't be disturbed by the change of magnet); third is the most possible one that they find the direction of the wave and the odor. The scientists also find that the female turtles transfer their DNA to their children without mixing with male turtles.
A Sea Turtle Has A Map Sense and a Compass Sense
Studies by Kenneth Lohmann and colleagues at the University of North Carolina at Chapel Hill have been instrumental in bringing to the forefront information about the relationship between sea turtles and geomagnetic navigation.
The results of the study showed that the turtle has a magnetic map that helps it know its position relative to a specific destination, such as feeding grounds, and may be used with the turtle’s compass—or directional—sense, as well as other environmental cues (such as the shoreline) to put itself on a course to reach that specific destination.
The Olfactory Section of the Turtle’s Brain
While researchers have long suspected that a sea turtle’s excellent sense of smell plays a role in navigation, a nasal structure called the Jacobson's organ is thought to be linked with the turtle’s geomagnetic skill. This organ is connected the olfactory bulb in the turtle’s brain. It is possible that small particles of magnetite, an iron ore, are located near the sea turtle’s nose, which help “stimulate the turtle’s brain with a sense of magnetic location,” according to Witherington.
Why Sea Turtles Must Know How to Orient Themselves
All of these advanced skills are important to sea turtles because, after hatching, they may spend up to five years floating in the ocean among various habitats specific to their species. For loggerhead turtles, the journey at sea to maturity is longer, maybe a decade. Each species of sea turtle has its preferred feeding grounds, and every female sea turtle instinctively returns to breed at the beach where she hatched—the same nesting site as her forebears. It is a part of her DNA. This faithfulness to the beach where she was born is called “natal philopatry.”
Perhaps one day researchers will know for sure all of the mysteries behind the sea turtle’s amazing instincts and navigational abilities. It is yet another example of how an animal considered ancient and perhaps simple has more advanced inner workings than man currently understands.

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