Lobsters used in the study were displaced 12 to 37 kilometers (7.5 to 23 miles) from their point of capture. Divers gathered the lobsters and placed them in containers partially filled with seawater. The containers were covered and transported to testing sites via circuitous routes by truck and boat. Further disorienting tricks were employed, such as suspending the containers by ropes so that they swung erratically, and lining them with magnets strong enough to alter the directional functions of compasses. Once at the test site, the lobsters, even with their eyes covered, invariably determined the direction of their capture site and began moving homeward.
"The physical displacement, with all the measures we took to confuse them, was to test the hypothesis of true navigationthat animals are not lost when taken somewhere completely new to them," Boles explained. "It's precisely the test that most animals fail. Once they pass, it implies that they somehow know where they are all the time, that something is built-in."
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Exactly how some animals are able to perform true navigation is not known. A leading theory suggests that the ability is based on magnetic mappingan animal's detection and use of the Earth's magnetic fields. Not all scientists subscribe to the concept, but the lobster study suggests that it may play a role.
Boles and Lohmann's experiments also tested the hypothesis that the lobsters were able to determine their locations by measuring even minimal differences in the Earth's magnetic field. The researchers wanted to learn how captive lobsters would react if they altered the Earth's magnetic fields to suggest to stationary lobsters that they had in fact been moved.
"We made extremely small changes in the magnetic field, subtle changes that most animals would ignore," said Boles. "[The captive lobsters] acted as if they were at the location that the magnetic field represented and ignored their actual physical location."
"That's very exciting, because many animals can navigate, like butterflies, whales, and salmon," said Walcott. "We know bits and pieces of what they do, but in no case do we really understand how they find a particular place. This is one of the first bits of evidence that the Earth's magnetic field plays a role in that ability."
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