Bogong moths rely on stars and magnetic fields to guide epic migrations

Each spring, billions of Agrotis infusa moths emerge across southeastern Australia, flying toward the Snowy Mountains' alpine caves to hibernate during summer. Come autumn, they return to their breeding grounds to reproduce and die. The new research, led by Lund University and involving teams from the Australian National University and the University of South Australia, uncovers the sensory and neurological tools that enable this feat.

"Until now, we knew that some birds and even humans could use the stars to navigate long distances, but this is the first time that it's been proven in an insect," said Eric Warrant, professor of zoology at Lund and adjunct professor at UniSA.

Using specially designed flight simulators in magnetically neutral conditions, scientists found that moths flew in accurate seasonal directions under natural night skies. When researchers rotated the star field 180 degrees, the moths reversed course. Scrambling the stars disrupted their orientation entirely.

"This proves they are not just flying towards the brightest light or following a simple visual cue," said Warrant. "They're reading specific patterns in the night sky to determine a geographic direction, just like migratory birds do."

When skies were clouded, the moths switched to using Earth's magnetic field alone, demonstrating a dual navigation system that adapts to variable environmental conditions.

The study also identified neurons in the moth brain tuned to star patterns and orientation, which activate most strongly when the insect faces south. These findings highlight the advanced navigational capacity of a species with a brain smaller than a grain of rice.

Researchers suggest this knowledge may help advance AI-based navigation in robotics and drones, and assist in conservation efforts, as Bogong moth populations have declined sharply and are now listed as vulnerable.

"This is not just about a moth... it's about how animals read the world around them," said Warrant. "The night sky has guided human explorers for millennia. Now we know that it guides moths, too."

The study builds on earlier work involving dung beetles and celestial navigation, which inspired AI sensors for low-light robotic applications, a project led by co-author and UniSA remote sensing engineer Javaan Chahl.

Research Report:Bogong moths use a stellar compass for long-distance navigation at night