科学60秒:海龟自带"指南针"
To find out, researchers strapped hatchlings into custom Lycra bathing suits, ___3___ to a tracking unit. They plopped each turtle into a small pool surrounded by magnetic coils. And they ___4___ the magnetic fields of Puerto Rico and the Cape Verde Islands, two points along the turtles' migration, with equal latitudes but different longitudes. The hatchlings swam opposite directions in the two trials—both being the right ones, to stay on the migratory track. The study appears in the journal Current Biology. [Nathan Putman et al., "Longitude Perception and Bicoordinate Magnetic Maps in Sea Turtles"]
The researchers say turtles may calibrate their migratory maps by sensing the magnetic field's intensity, and its inclination to the Earth's surface—a combo that gives each point of the migration a unique signature. As for any human navigators out there, you'll just have to ___5___ for a GPS.
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