Bogong moths are an extraordinary species. Each spring, they make a round-trip migration of up to 1,000 kilometers to get to remote limestone caves in the Australian Alps. In fact, scientists have been trying to understand why these tiny insects are able to find their way across thousands of miles with such incredible accuracy. New research indicates that Bogong moths indeed navigate the heavens, deploying a stellar compass. They have the ability to detect the Earth’s magnetic field. The remarkable navigational ability of these little parrots has baffled scientists for years.
Bogong moths undertake the longest migratory journey of any insect species. That’s the equivalent of a human completing two circumferences of the Earth—and doing it just on their own sense of sight and sound. They find their way by using both the stars and the Earth’s magnetic field. It is with this tremendous twosome that they’re led into—and further through—their nighttime journey.
The Stellar Compass of Bogong Moths
Bogong moths have developed an extraordinary method of navigation. In fact, they’re able to use a stellar compass to navigate by stars and fly at night! This change allows them to point themselves in the right direction — a more complicated task in the dark. These nocturnal moths are incredibly reliant on the visual cues provided by a starlit sky. They in particular deploy the Milky Way as a prominent wayfinding feature in the Australian outback.
Eric Warrant, a professor at the University of Lund in Sweden, explains why this natural phenomenon is so important. As he puts it, “If you go out into the Australian bush at night, what you’ll see is breathtaking. The Milky Way, in fact, is one of the most beautiful and pronounced visual markers. This beautiful dependence on celestial navigation raises some questions. How do these insects manage to navigate when they are placed under various stressful environmental conditions?
As we learned from a groundbreaking 2018 study published in Nature, Bogong moths possess an extraordinary migration precision. Their ability to navigate well even when deprived of the Earth’s magnetic field, under a simulated natural starry night sky—Warrant added, “The largest surprise was finding out that bogong moths are able to migrate underneath a simulated version of their natural local starry night sky. They can accomplish this even in the flat-out absence of Earth’s magnetic field.
The Role of Earth’s Magnetic Field
In addition to their stellar compass, Bogong moths possess another navigational tool: they can sense the Earth’s magnetic field. This lack of field awareness means that unaware birds will be unable to change course, even when given the opportunity. Then, in a series of experiments, researchers flipped an artificial night sky upside down. This led to the moths changing course to fly more directly towards the light. The warrant explained that the moths had to depend on their last surviving cue—Earth’s geomagnetic field. This result by itself demonstrates that they have both an excellent compass and a magnetic compass.
The scientific community is just beginning to unpack how exactly Bogong moths are able to pick up on this magnetic field. Warrant speculates that they use a system based on a chemical reaction with the proteins called cryptochromes. Aside from magentoreceptors, these light-sensitive proteins might be used to control other cells that sense magnetic fields. This new finding shows just how complex insect navigation really is.
“They’re very exciting questions that we’re asking,” Warrant said. These questions are wildly cool, though! We’re studying them in an animal that possesses arguably the smallest nervous system, small brain, and smallest eyes in the vertebrates. Even today, the details of how such a small and seemingly simple organism is able to migrate so far are still fascinating scientists.
Ongoing Research and Future Directions
Currently, researchers are mapping out the sensory pathways involved in the Bogong moths’ migration. Their goal is to improve our understanding of the way these insects integrate multiple navigational strategies in order to arrive at their intended destination. Charges Warrant, “we are just getting started on the second question, which is ‘what do we do about this.’” Their goal is to figure out what sensory cues are associated with the place.
The research team’s efforts involve constructing non-magnetic laboratories where they simulate both the night sky and Earth’s magnetic field. This isolated environment helps researchers run controlled experiments to better understand how these insects navigate while controlling outside forces that can harm the insects’ navigational abilities.