How Bogong moths use stars as a compass

Every spring, billions of small, unassuming moths take off from farmlands and grasslands across southeastern Australia. Their destination? A handful of cool, dark caves tucked high in the Australian Alps. What makes this extraordinary is not just the sheer number of moths, sometimes enough to carpet cave walls sixteen thousand thick, but the fact that each individual is making this journey for the very first time. They've never seen these mountains before. Yet somehow, they find their way.

A study published in Nature has revealed just how Bogong moths (Agrotis infusa) manage this feat: they navigate by the stars.

The Bogong moth is one of Australia's most incredible migrants. Each spring, after emerging from the ground, they launch into a journey of up to 1,000 kilometers, flying by night toward alpine caves where they spend the summer in dormancy, a period scientists call "aestivation." Come autumn, the very same moths leave their mountain hideaways and return north to breed, and die. Their offspring will repeat the journey the following year, guided not by memory, but by instinct.

For decades, scientists have known that Bogong moths use Earth's magnetic field to stay on course. But magnetic information alone is not always reliable. Local anomalies or geomagnetic storms can distort the compass. That raised a question: what other tools might these tiny travelers carry in their navigational toolkit?

To answer that, an international team consisting of researchers from Lund University in Sweden, the Francis Crick Institute in London, Nanjing Agricultural University in China, and the Australian National University designed ingenious experiments.

They tethered migrating moths in a specialized flight simulator that allowed the insects to flap their wings freely while researchers carefully manipulated what they could see. Under natural moonless skies, but with Earth's magnetic field switched off using a set of coils, the moths still managed to orient themselves correctly: southward in spring, northward in autumn. When the scientists rotated a projected starry sky by 180 degrees, the moths flipped their orientation almost exactly. And when the stars were scrambled into random positions, the moths became disoriented, flying in no consistent direction at all.

The conclusion was unmistakable: Bogong moths are using the starry sky itself as a compass.

The team also recorded activity inside the moths' brains, focusing on regions known to be involved in navigation. Neurons in the optic lobes, central complex, and lateral accessory lobes responded directly to rotations of the starry sky. Many of these neurons fired most strongly when the moth was "facing" south, no matter the season.

This means that Bogong moths don't just passively react to light. Their brains have dedicated circuits tuned to the patterns of the Milky Way and other celestial features, making them capable of long-range, inherited navigation on par with migratory birds.

Humans have used the stars for navigation for millennia. Polynesian voyagers, for instance, crossed vast ocean stretches guided by constellations. Birds are also well known for star navigation. But until now, no invertebrate, no insect, had been shown to use stars to travel in a specific geographical direction toward a distant destination. So, the discovery places the Bogong moth in a rarefied club of celestial navigators, alongside sailors, birds, and perhaps even seals. And it challenges us to rethink what tiny insect brains are capable of.

Also, these moths are a keystone species in Australian ecosystems. Their migrations feed countless animals, from birds to bats to endangered mountain pygmy-possums, which time their breeding to the moths' arrival. In recent years, however, Bogong moth populations have plummeted, raising alarms about climate change, agricultural chemicals, and light pollution disrupting their epic journeys. So, understanding how Bogong moths navigate matters.

If moths rely on the stars to find their way, what happens when the night sky is drowned out by city lights? Could light pollution be contributing to their decline, in the same way it confuses migrating birds and sea turtles? The researchers suggest that preserving dark skies may be as important for moths as protecting habitat on the ground.

If you want to learn more, read the original article titled "Bogong moths use a stellar compass for long-distance navigation at night" on Nature at http://dx.doi.org/10.1038/s41586-025-09135-3.