Bogong Moths Are First Nocturnal Insects To Use Earth’s Magnetic Field To Guide Their Movements

Bogong Moths Are First Nocturnal Insects To Use Earth's Magnetic Field To Guide Their Movements
John Tann / Flickr/Cropped and Resized (CC BY 2.0)

The tiny Australian Bogong moth is known to fly more than 600 miles to find shelter from the blistering summer heat, despite its small size. That’s just one reason why this insect stands out in the animal kingdom, however, as a new study suggests that it is the first nocturnal insect to use Earth’s magnetic fields to guide its seasonal flight path.

In a new study published in the journal Current Biology, researchers detailed how Bogong moths share something in common with different species of birds, fish, and sea turtles, and are able to use our planet’s magnetic fields, along with their natural vision, as a means of navigation. These moths use this unusual capability to make them the only other insect aside from monarch butterflies to fly a long distance toward a specific location — in the Bogong moths’ case, that location is a series of caves in the Australian Alps.

“This particular species is interesting because we know exactly where they’re going,” explained University of Lund (Sweden) research fellow David Dreyer, as quoted by Discover Magazine.

Together with a multinational team of researchers that also included University of Lund professor and neuroethologist Eric Warrant, Dreyer captured Bogong moths as they traveled through their migration routes, which were always to and from the same locations, with the insects flying southward to the Australian Alps in the spring, and back north in the fall. The captured moths were then tested in a flight simulator that was previously created for researchers to study monarch butterflies and their migration paths.

In order to ensure that the moths used the flight simulator like they were expected to, the researchers took a series of steps, first attaching the moths to long shafts that tracked their flight direction, then placing a cylindrical barrier around the insects, with “a few simple shapes” as mock visual landmarks, and setting up a magnetic coil to simulate Earth’s magnetic field. Finally, satellite images of the Australian countryside were projected onto surfaces underneath the moths, to give them the impression that they were making their seasonal journey as usual.

According to Discover, the Bogong moths regularly flew toward the simulated landmarks when they were kept in place, with the direction of the mock magnetic field aligned accordingly. They were also observed to tweak their flight paths when the scientists adjusted both the landmarks and magnetic field. Interestingly, the insects started flying around at random, appearing “disoriented” when the researchers displaced the magnetic field in such a way that it was not aligned with the landmarks.

In what turned out to be an unexpected twist, the researchers found that the Bogong moths didn’t immediately get disoriented when the magnetic fields were switched up. According to Warrant, it took “a couple of minutes” before the moths realized that things weren’t like they were supposed to be in the flight simulator. That hints at the insects using their eyesight as their main navigational tool, with Earth’s magnetic fields serving as a way for them to make sure they’re on the right path.

“It’s almost like they put their compass back in their pocket, if you like, and check the field only every couple of minutes,” said Warrant.

Though there are still a few unanswered questions, the researchers believe that Bogong moths “definitely” can sense magnetic fields, and use both visual and magnetic senses to make their way around. Going forward, both Dreyer and Warrant are hoping to determine where the insects’ magnetic sensors are located by measuring changes to the electrical signals in their brains.