Swarms of Bogong moths have returned to Australia in numbers not seen for nearly a decade, signaling a hopeful resurgence of a species that faced a dramatic population collapse. Once a common sight each spring, the annual migration of these moths along Australia’s east coast had nearly vanished after a sharp decline beginning in 2017, attributed to drought, pesticide use, and habitat loss.
The Bogong moth migration, a natural spectacle involving billions of insects traveling to cooler alpine regions, was a well-known event. The moths would settle in mountain caves, creating dense mats on the walls and becoming an important part of the ecosystem. Their return has been met with enthusiasm by scientists who study their ecological role and remarkable navigation abilities.
“This is what nature should be,” said Marissa Parrott, a conservation biologist with Zoos Victoria, describing the emotional response to witnessing the dense moth swarms once again. In peak years prior to the collapse, as many as four billion Bogong moths would migrate inland to the Australian Alps, a journey that also supports critically endangered species such as the mountain pygmy possum.
Research conducted by scientists including Western Sydney University’s Eleanor Drinkwater has shed light on the moths’ navigation techniques. By observing tethered moths under artificial starry skies, researchers discovered that Bogong moths use the Milky Way for celestial navigation—a rare example of such behavior in invertebrates. This remarkable ability guides them on their extensive migratory route.
The moths also play vital ecological roles, aiding plant pollination and serving as a food source for various wildlife. Their presence is so notable that they even disrupted the Sydney 2000 Olympic Games when radar systems mistook large swarms for rain clouds.
Despite this encouraging recovery, scientists remain cautious. The population retreat since 2017 had reached an estimated 99.5 percent loss. Observers found caves nearly empty during the worst years, causing alarm among conservationists. Factors behind the recent rebound are still under investigation, but wetter weather conditions in recent seasons are believed to have contributed to improved survival and migration.
Looking ahead, experts express concern over a predicted severe El Niño event that could bring hotter conditions throughout the Australian summer, potentially threatening the Bogong moth’s fragile recovery. “It’s great they’re back, and we’re really excited they’re back,” said Drinkwater. “But we’re still worried about them.”
As Australia welcomes back one of its most iconic migratory insects, researchers continue monitoring the Bogong moth population closely, hoping the revival will endure and signaling a small but important victory for conservation efforts.