Bogong moths navigate using a light-dependent geomagnetic inclination compass

Abstract Bogong moths (Agrotis infusa) migrate biannually up to 1,000 km between their breeding areas and geographically restricted aestivation sites in the Australian Alps 1,2 . These moths navigate towards their distant goal using the stars as a compass 3 but navigate correctly even when the stars are obscured by clouds 3 , suggesting that their magnetic sense 4 likely harnesses the Earth’s magnetic field as a compass. However, the nature of this compass, and of the magnetic sense underlying it, remain unknown. Here we show that Bogong moths, tethered in a flight arena under a full-spectrum randomised starry night sky, navigate in their inherited migratory direction using the geomagnetic field alone. If both field inclination and polarity are turned by 180°, or if inclination is turned alone, moths fly in the opposite direction. If polarity is turned alone, moths fail to turn. Furthermore, if violet-blue light (380 nm < λ < 500 nm) is removed from the illumination spectrum, or if tethered moths are exposed to weak broadband radiofrequency fields (150 kHz – 60 MHz), magnetic orientation is abolished. Our results indicate that Bogong moths use the geomagnetic field as an inclination compass for long-distance navigation at night and possess a light-dependent radical-pair-based magnetic sense 5 .