Australian Moths Navigate 1000 km Journeys Using the Stars as Their Compass

Traveling distances exceeding 1,000 kilometers to escape the summer heat, Australia’s moths have been identified as the first invertebrates to utilize stars for navigation on long migrations.

Every spring, billions of bogong moths (Agrotis infusa) embark from various regions of southern Australia, surviving the winter as caterpillars by feeding on vegetation before retreating to the cool caves of Australia’s Alpine regions. Once in the caves, they enter a state of dormancy known as estivation until they return to breeding grounds.

The recent decline of these moth populations has led to inquiries about their navigation methods in reaching high-altitude caves, as noted by Andrea Aden from the Francis Crick Institute in London.

Previous studies have demonstrated their ability to use Earth’s electromagnetic fields but only in conjunction with visible landmarks. Aden and her team sought to explore other potential cues that moths might use for navigation.

“When you venture into the Australian bush at night, one of the most striking visual markers is the Milky Way,” she explains. “We know that diurnal migratory birds rely on the sun, so testing whether moths use the starry sky seemed like a logical step.”

To investigate, the team employed light traps to capture moths during migration and transported them to a laboratory. There, they were placed in a Perspex arena with images of a night sky projected overhead. Moths were free to choose their flight direction based on the sky images while the Earth’s magnetic field was neutralized using a Helmholtz coil.

Experiments revealed that moths did utilize a stellar compass, according to team member Eric Warrant from Lund University, Sweden. “When the tethered moths were placed under a realistic starry sky, they oriented themselves towards their migratory direction,” he states. “They achieved this solely with the assistance of these stars, independent of other visual cues and the magnetic field.”

When the simulated starry sky was rotated 180 degrees, the moth flew in the opposite direction. Randomizing the star placements in the image left them disoriented.

In a subsequent experiment, very thin electrodes were implanted in the moth’s brain, revealing changes in neural activity as the projected starfield was rotated.

While dung beetles are known to maintain a consistent bearing using the Milky Way, no other insect species has previously demonstrated this level of celestial navigation.

“The bogong moth is the first invertebrate documented with the ability to navigate long distances using stars as a compass—a phenomenon previously recognized only in certain birds and humans,” Warrant states. “This capability is truly remarkable.”

Another insect recognized for its extensive migrations, the Monarch butterfly (Danaus plexippus), primarily relies on the sun supplemented by the environment.

Cody Freas from Macquarie University in Sydney, Australia, emphasized the incredible efficiency of insect navigation, stating, “Stellar navigation showcases the remarkable visual acuity found in nocturnal insects, enabling them to utilize various cues (Sun, Moon, Stars) even in low-light conditions,” adds Freas.