The experiments show for the first time that bottlenose dolphins have a sensory basis for using the Earth’s magnetic field for orientation, said neuroscientist Guido Denhardt from the Institute of Life Sciences at the University of Rostock. At least there is potential for this. “It’s fair to say that dolphins have this ability.”
The research team includes biologist first author Tim Hüttner (University of Rostock/Tiergarten-Nuremberg), physicist Lars Miersch (University of Rostock) and Lorenzo von Fersen from Tiergarten-Nuremberg.
The phenomenon is known only in some mammals.
The so-called electroreception has long been known in sharks and rays. “The shark is the ultimate electrical specialist among marine animals,” says Denhardt. Among mammals, electroreception has been demonstrated in the platypus, the short-beaked echidna, and, in 2012, the Guiana dolphin. And now with a bottlenose dolphin.
Animal subjects “Dolly” and “Donna”
The new findings were based on experiments with dolphins “Dolly” and “Donna” at Nuremberg Zoo, where the dolphins have been kept since 1971. There, animals in the dolphinarium first learned to swim underwater in an experimental apparatus made of PVC pipes in order to stay there. They put their faces on the shelf. If there is an electrical signal, you should leave the device again. If there is no signal, you should wait in the device for at least twelve seconds. Correct decisions were always rewarded with fish.
The animals sensed electric fields through nerve-rich so-called vibrissae pits on their upper beaks. Young animals have small tactile whiskers (vibrissae) that help them in the not so easy task of finding their mother’s nipple. The experiments also showed that Dolly and Donna responded slightly differently depending on the strength of the electric fields. “But it was minor,” Huettner said.
Lots of training in advance
Before Donna and Dolly were ready, researchers and a team of trainers led by dolphin keeper Armin Fritz had to spend a lot of time. Donna and Dolly trained for a year and a half until they began measuring electric fields. “This is due to very, very weak direct current fields, which cannot be perceived without the corresponding receptors,” says Hüttner. “One day I put my hand under it. Nothing happened”.
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