A recent study published in Nature confirmed that Bogong moths navigate using the starry sky of the Milky Way, a capability previously recorded only in humans and some migratory birds, making them the first invertebrates known to have this ability, according to The New York Times.
The Bogong moth (Agrotis infusa) undertakes a remarkable journey each year. Every spring, billions of these moths embark on an epic migration of over 1,000 kilometers from the plains to the cool alpine caves of the Snowy Mountains in Southeast Australia to escape the summer heat, where they enter a state of dormancy called aestivation. This extraordinary behavior intrigued scientists for decades.
"We've always thought, 'Oh, they are just simple animals, they just fly toward lights and these kind of things.' But the brain network and the ability of these animals to perform quite extraordinary and complex navigational tasks is just mind-blowing," said Dr. Basil el Jundi, one of the researchers involved in the study, according to The New York Times.
The research team, led by an international group of scientists from Lund University in Sweden, investigated the neurological basis of this behavior. They identified specialized neurons in the Bogong moth's brain that respond to the orientation of the starry sky, marking the first discovery of such neurons in an insect. These neurons fire most strongly when the moth is facing southwards.
To study which visual markers Bogong moths were using to migrate, the researchers created a flight simulator for captured moths. In the flight simulator, they imitated what a migratory flight would be like by projecting a realistic version of the moonless night sky onto a screen while blocking all possible magnetic fields. When presented with a natural starry sky, the Bogong moths consistently flew in the correct migratory direction for the season: south in spring and north in autumn.
"When the stars were scrambled into random places, the Bogong moths became disoriented, losing their orientation completely," reported ABC Color. This confirmed that the moths rely on the stars for navigation.
"This proves they are not just flying towards the brightest light or following a simple visual cue. They're reading specific patterns in the night sky to determine a geographic direction, just like migratory birds do," said Eric Warrant, a neurobiologist at Lund University and one of the study's authors, according to EurekAlert.
Despite having brains smaller than a grain of rice, these moths managed to navigate accurately over long distances, using magnetic and visual signals.
Researchers also discovered that when the starry sky was rotated 180 degrees, the moths immediately changed their flight direction accordingly, confirming their reliance on the stars for navigation. Conversely, when shown a random starry sky without the Milky Way, the moths became disoriented and lost their ability to migrate in their inherited direction.
The study underscores the importance of protecting the migratory pathways of Bogong moths, which have drastically declined in recent years and have been listed as vulnerable, pointing to the impact of urbanization and light pollution on their migratory paths. The researchers believe that understanding how these moths navigate may help in conservation efforts.
"Understanding how their migration works, and which cues they use to navigate, may help us protect these insects, which in turn helps the entire alpine ecosystem of which the moths are an integral part," explained Andrea Adden, a neurobiologist at the Francis Crick Institute and one of the researchers, according to NPR.
The findings of this study not only solved one of nature's great migratory mysteries but also expanded our understanding of animal-guidance mechanisms. The ability of Bogong moths to navigate using stars is remarkable considering their brain is approximately one-tenth the volume of a grain of rice and their eyes only a couple of millimeters wide.
"That moths can manage such precise travel puts me in awe," said Kenneth Lohmann, a biologist at the University of North Carolina, who was not involved in the study, according to Popular Science.
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