These moths use the stars to navigate on an epic migration

Bogong moths migrate hundreds of kilometres and back each year using the southern night sky as their compass

Bogong moths (*Agrotis infusa*) use the night sky to help navigate hundreds of kilometres.Credit: Tasso Taraboulsi/Polaris/eyevine

Each spring, billions of Bogong moths (Agrotis infusa) migrate hundreds of kilometres south to the Australian Alps, guided by the austral night sky. The discovery that they can find their way using only the stars — reported in an 18 July Nature paper¹ — makes this moth the first invertebrate to be observed using celestial navigation for long-distance journeys.

“The first time we saw them flying under the night sky with no other cue and flying in the right direction we had to hold on to the edge of the table,” says study co-author Eric Warrant, an entomologist at Lund University in Sweden.

Bogong moths emerge from their cocoons in southeastern Australia and some regions of New Zealand and begin the long flight to mountain caves that they have never previously visited. The following autumn these moths make the return flight to reproduce and die. “How on earth do they know how to find their way there?” Warrant says.

Warrant and his team suspected the moths were guided by looking at the stars, an ability previously identified only in humans, birds, and possibly seals. To test this, they captured wild moths and placed them in a ‘flight simulator’ — a clear cylindrical box in which the insects were tethered and their movements recorded while being shown projections of the starry sky.

The researchers manipulated the magnetic field in the simulator to observe whether moths could navigate without this cue. They also recorded the activity of visual neurons in the moths’ brains to investigate whether they have an internal representation of the starry sky.

Celestial compass

When the moths did not have access to the projection of the sky or to the electromagnetic field, they were unable to navigate at all. But with access to only the visual cue of the stars, they were able to navigate in the seasonally appropriate direction. They were also able to fly in the correct direction in the presence of an electromagnetic field, but no visible stars.