Yes, we’ve heard bees use the Earth’s magnetic field to navigate by. We’ve also heard about some bird species following the Sun to find the location of their evening roost. But what do we know about the animals living at sea? Do they use astronomical aids to help them find their way around the planet? Mammals such as whales are known to exhibit “skyhopping” behaviour when they surface from the water to have a look around, but seals go one step further; they can recognise and orientate themselves with the stars…
It was one of the first methods us humans used for navigation when sailing across the middle of a featureless ocean, we’d pick out known stars and constellations and relate them to our location on the planet’s surface. Explorers used astronomy to guide them to new lands, captains used the stars to direct their battleships toward the enemy and trade routes were repeatedly used thanks to star navigation. In its most basic form, star navigation could be carried out by linking stars with the location on the horizon when they rise, as was traditionally done by Polynesian sailors to colonize vast numbers of islands in the Pacific.
In a revealing study, researchers at the University of Southern Denmark in Odense have discovered that seals have the ability to recognise stars and groups of stars inside a modified planetarium. A five-metre round pool plus two harbour seals were covered with a dome with 6000 point light sources to simulate the Northern Hemisphere’s starry sky. BjÃ¶rn Mauck and his team found that if they selected an individual star with a laser pointer, they could train the seals to swim toward that star and then rewarded them with a treat if they did it correctly. Then the researchers would randomly orientate the dome, and without the help of a laser pointer, the seals would continue to swim toward the correct star.
“Seals and many other animals are exposed to the starry sky every clear night, and thus certainly have sufficient opportunities to learn the patterns of stars.” – BjÃ¶rn Mauck
This study strongly suggests that these two harbour seals have an amazing, natural ability to recognise the distribution of stars on a clear night.
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So when you next see a seal popping to the ocean surface, it might not be simply checking out its surroundings, it might be trying to look for Sirius in the constellation of Canis Major…
Paper abstract: “Harbour seals (Phoca vitulina) can steer by the stars“, Mauck et al., 2008
Source: New Scientist