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Since ancient times, human beings have known to rely on the stars in the night sky to indicate the direction, but there are many animals that know how to use the stars to navigate. From dung beetles, songbirds to seals, mastering star navigation is a vital survival skill, which can help them to migrate, find food and even find mates.
Like many migratory songbirds, the North American indigo bunting flies south for the winter, and they prefer to fly at night. During the migration season, the indigo bunting will jump in the direction it wants to go before taking off to determine its course.
However, when researchers in Michigan removed constellations that mimic the 35 degree range of Polaris in the night sky, the songbirds lost their sense of direction, were unable to determine where the North was, and could not use the information to fly south.
Harbor seals, a marine mammal living along the Atlantic and Pacific coasts of the northern hemisphere, spend a lot of time foraging at night. In these cases, they lack landmarks to indicate direction.
But scientists in Germany and Denmark have found that harbor seals use specific stars as navigation clues to stay away from the coast, the first scientific evidence that marine mammals are oriented through stars. This star based navigation is likely to enable seals to effectively search an area for food.
The researchers say seals can see individual stars because their eyes are very much like cameras, and the joint action of cornea and lens is equivalent to a convex lens, which gathers light from objects on the retina to form an image of the target object. This structure allows a lot of light to enter, which helps seals detect relatively dim objects such as stars.
Insects, by contrast, dont see a single star because their compound eyes cant detect tiny details like a single point of light. But galaxies such as the Milky way can be seen as luminous streaks, a useful reference for the nocturnal African beetle s.satyrus.
In order to compete for fresh dung more effectively, dung beetles usually move in a straight line to cross the longest distance in the shortest time. For this reason, s.satyrus usually needs the polarized light navigation of the moon. Without the moon, the Milky way would be an alternative to navigation.
S. satyrus is the only animal that has been shown to be able to navigate the galaxy, the researchers said. As long as they remain in the same direction as their initial position, they move in a straight line.
In addition to the indigo bunches, harbor seals and dung beetles mentioned above, there may be more animals navigating through the stars. For example, preliminary evidence suggests that European robins, yellow back winged moths and even crickets and frogs can do it.
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