Bogong Moths Use the Night Sky to Navigate up to 1000 Kilometres

Every spring, Australia’s iconic Bogong moths leave their birthplace in southeastern Australia and set course for a very specific destination they never visited before: dark, cool caves and rocky outcrops in the Snowy Mountains of southern Australia.

Here, the moths spend the summer months in dormancy, before returning in autumn to reproduce and die. When spring comes again, the cycle repeats. Each time, around four million Bogong moths undertake the journey, which can be up to 1000 kilometers long.

In a new study published in Nature, an international team of researchers demonstrates that Bogong moths use star constellations and the Milky Way to navigate many hundreds of kilometers during their annual migration. This makes them the first known invertebrate to use a stellar compass for long-distance travel.

The brain is lighter than a pinhead

The researchers are from Lund University in Sweden, the Australian National University, the University of South Australia, and the University of Southern Denmark, where postdoctoral researcher Jingjing Xu from the Department of Biochemistry and Molecular Biology contributed to the study. She also studies the European robin and tries to unravel how it finds its way between Denmark and Africa using a magnetic compass.

“The Bogong moth is a tiny insect with a brain lighter than a pinhead. So how can it navigate so accurately at night and find a place it’s never been before? That fascinates me,” says Xu, adding:

“The night sky over the Australian Snowy Mountains was just vast and breathtaking. When I stood there and looked up, I was completely awestruck. In that moment, it all made sense—under such a bright, brilliant Milky Way, why wouldn’t insects be able to navigate by the stars?

According to the researchers, it has long been known that some birds — and even humans — can use stars to navigate over long distances.

“But this is the first time the that it’s been proven in an insect,” says one of the lead authors of the paper and professor of zoology at Lund University, Eric Warrant, in a joint press release.

To understand how Bogong moths manage the long journey without getting lost, the researchers set up a series of experiments. These included advanced flight simulators and brain activity measurements in controlled, magnetically neutral environments. Each setup aimed to examine how the moths orient themselves under different sky conditions.

When the stars are obscured by clouds

When exposed to a natural starry sky without a magnetic field, the moths consistently flew in the correct direction — south in spring and north in autumn. When the star pattern was rotated 180 degrees, the moths reversed direction accordingly. But when the star pattern was scrambled, their orientation vanished.

“That proves they’re not just flying towards the brightest light or following a simple visual cue. They’re reading specific patterns in the night sky to determine a geographic direction, just like migratory birds do,” says Warrant.

But what happens when the stars are obscured by clouds? The moths maintain their direction — using Earth’s magnetic field alone. In other words, they rely on a kind of dual-compass system to ensure reliable navigation even in variable conditions.

The neurobiological basis

The research team also delved into the neurological basis of this behavior. They discovered specialized brain cells in the moths that detect the positions of stars in the sky. These cells are located in brain regions responsible for navigation and are most active when the moth faces south.

Jingjing Xu also studies the robin’s navigational skills. Her research focuses on uncovering the neurobiological and molecular mechanisms that come into play when a robin uses its internal magnetic compass to navigate.

During her doctoral research, Xu and her colleagues have discovered a magnetically sensitive protein called cryptochrome 4a in the retina of night-migratory robins (Xu et al., Nature 2021). Currently, Xu is investigating the magnetosensory protein networks in retina neurons.

Maybe also bats, fish and ants

"This protein is believed to play a central role in the birds’ ability to sense Earth’s magnetic field—a process thought to rely on quantum mechanical interactions known as the radical pair mechanism. As such, bird magnetoreception stands out as one of the rare and fascinating examples of quantum biology in action", Xu says.

If evolution has indeed crafted a quantum compass in birds, it raises an exciting possibility: could other nocturnal navigators possess a similar system? After her research on birds, Xu continued this line of inquiry, to uncover how other animals across the tree of life sense magnetic fields. She and her colleagues discovered the magnetic compass in Bogong moth, discussed in this article.

A number of other animals are under investigation for their potential magnetic sense, including bats, fish, ants and mole-rats.