I am really sorry that I didn’t write much in the last time. I am preparing my first paper, and that is a little bit time and energy consuming. Nevertheless, I have to share this jewel of a paper with you: “How animals follow stars” (James J. Foster, et al. 2018). When I read the paper I was immediately on fire: animal follow stars? I could not imagine that. So I had to read it. Some people debate if our destiny is written in the stars. However, I guess nobody questions that your current location and direction are hidden in the stars above you. In history, sailors used that fact to navigate their ships in the night. Fixed stars like the Polaris can help for directions, and experienced sailors can see the latitude of their location by watching the patterns of stars. If you have a good clock with you, you can even find out the longitude (you need the clock to calculate the earth rotation which produces the same shift in star patterns as a change in longitude). So all in all, humans are able to navigate by stars. The question is if there are also animals which use the stars for their navigation. Orientation by fix stars, for example, require learning to identify individual stars by their configuration. Therefore, animals which would be able to navigate by stars, need a certain “intelligence” and “eye quality”. However, that restriction does not exclude too many species. Therefore, many different scientists analyze the behavior of many different species under the artificial sky of a planetarium or after a geographical displacement (and therefore “different” natural sky). What should I say? There is evidence that some birds can use star clues for their migration. Moreover, night-flying moths seem to orient on both the moon and the star, even though they don’t do that perfectly. Moths show a drift over time, which could be a result of lacking time-compensation for celestial rotation. Of course, there are also non-flying animals which show a talent for star navigation. For example, you can train seals to identify specific star patterns, but the question is if they use that in their natural habitat. What I found most interesting in the review of James J. Foster, et al. (2017) is the story about the ball-rolling dung beetles. Such a dung beetle does not make large journeys which need precise navigation, but nocturnal species like the Scarabaeus satyrus seem to use celestial cues to maintain their initial heading when rolling their dung ball. That prevents them from returning to their point of origin. Planetarium experiments showed that Scarabaeus satyrus use the Milky Way as the primary stellar orientation cue. Of course, the little dung beetle does not see the Milky Way like we do. An experimental study which used an artificial ‘Milky Way’ band consisting of LED lights, showed that their orientation is based on a brightness comparison. It is suggested that the beetles may identify the angle of a bright sky region or the direction of a broad-field brightness gradient. Isn’t that amazing? A small beetle using the large sky to roll their dung home safely!
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IdeaI love to increase my general science knowledge by reading papers from different fields of science. Here I share some of them. Archiv
März 2018
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