What Animals See in the Stars, and What They Stand to Lose
Nick, a harbor seal, entered the annals of astronomical history when Guido Dehnhardt, a marine biologist now at the University of Rostock, was studying how marine mammals orient themselves. If seals could discern stars, Dr Dehnhardt and his colleague Björn Mauck hypothesized that it might help explain how animals are able to swim long swims through otherwise featureless seas.
To test the astronomical skills of a seal, Dr. Mauck devised what must be two of the most awe-inspiring and amazing experiments in scientific history.
First, the team built their seal-o-scope – a lensless tube, through which Nick circled the night sky. He was constantly pushing down on his paddle when bright spots like Venus, Sirius and Polaris appeared; he couldn’t see as many faint stars as humans can, the researchers determined, but many possible celestial landmarks were still available to him.
Then Dr Mauck built something even bigger. This time two Seals were invited to participate, Nick and his even smarter brother, Malta.
When brought back to a pool at a Cologne zoo, the seals entered a dome measuring 15 feet in diameter, its edge resting on a floating ring. The interior of this bespoke aquaplanetarium was illuminated with 6,000 simulated stars. “They immediately swam across the planetarium and looked at stars like, ‘Oh, what is this?'” Said Dr Dehnhardt. “You feel like they really recognized what it is.”
The researchers first used a laser pointer to point the seals to where the edge of the dome met the water closest to Sirius, the Dog Star. If a seal swam and touched that particular part of the dome with its snout, it would receive fish. Then the pointer was pointed directly at Sirius. Again, the seal’s task was to swim towards the star and touch the tip of the edge just below.
Then the researchers gave up the laser pointer. Regardless of the orientation of the star projector, the two seals could possibly swim towards Sirius. This showed, the researchers argued in a 2008 article, that seals crossing the high seas had the ability to use lodestars to guide their journeys.
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