The Bogong moths of Australia may not be the most visually striking insects, but their remarkable migratory behavior is nothing short of extraordinary. According to Andrea Adden, a neurobiologist at the Francis Crick Institute, these small brown moths, adorned with arrow-like markings on their wings, engage in an epic migration twice in their lifespan, traveling hundreds of miles in each direction.
Researchers have demonstrated that the Earth's magnetic field plays a crucial role in helping Bogong moths orient themselves during their migration. However, Adden points out that magnetic orientation alone is insufficient. Visual cues are essential, especially when navigating vast landscapes at night, where natural light is minimal. This need led her to investigate what visual cues might aid these moths in their incredible journey.
In a groundbreaking study published in the journal Nature, Adden and her colleagues revealed that the starry sky serves as a critical navigational cue for Bogong moths. This research marks the first instance of an invertebrate utilizing the stars for navigation and the discovery of neurons that specifically respond to the celestial display in the insect brain.
The annual migration of Bogong moths follows a rhythmic pattern. They hatch in southeast Australia during the spring, but due to the intense summer heat, immediate reproduction is not feasible. Adden explains that if the larvae were to hatch right away, they would struggle to find enough food. Instead, these moths embark on a remarkable journey over several nights, traveling more than 600 miles south to the cooler Australian Alps, where they enter a dormant phase known as estivation—similar to hibernation but occurring in summer.
In the Alps, millions of moths congregate in caves, creating an overwhelming sight—moths clustered densely such that the cave walls are hardly visible. In the fall, these moths return to their breeding grounds to mate, lay eggs, and die, completing their life cycle. Remarkably, the following year, new moths hatch without any prior experience or parental guidance, yet they instinctively navigate back to the mountains.
To investigate the potential role of stars in moth navigation, Adden, during her Ph.D. at Lund University in Sweden, and her colleagues conducted experiments with moths captured in the Australian Alps. They placed the moths in a mini-planetarium that projected the night sky while eliminating magnetic fields. Although this experiment relied on the moths’ cooperation, the results were astonishing.
Rather than merely fluttering aimlessly, the moths exhibited stable directional choices aligned with their migratory path, demonstrating that they use the starry sky as a compass to navigate through the darkness.
Curious about the neurological mechanisms behind this behavior, Adden further recorded the electrical activity of individual neurons in the moths’ brains while projecting the Milky Way. She discovered that the majority of neurons in the visual processing regions became active when the moths faced south. This suggests that the moths’ brains encode directional information by interpreting visual cues provided by the stars.
Biologist Pauline Fleischmann from the University of Oldenburg, who studies navigation in desert ants, expressed her fascination with Adden's findings. She noted that this research indicates that the world of insects is rich with information, far more complex than often assumed. The ability of Bogong moths to utilize both visual and magnetic cues for navigation is crucial for their survival, particularly in situations where one system may fail—such as during cloudy weather or magnetic disturbances.
Unfortunately, Bogong moths are currently endangered. Adden believes that her findings could be vital in efforts to conserve these remarkable insects and the ecosystems that depend on them. A crucial first step towards their protection is reducing light pollution, which can interfere with their star-guided migratory routes across the Australian bush.
In conclusion, the migration of Bogong moths is not just a story of survival; it is a captivating example of the intricate relationship between insects and their environment. By studying these small yet significant creatures, researchers can uncover valuable insights into navigation and conservation strategies that benefit biodiversity as a whole.
