The Australian Bogong moth uses the stars of the Milky Way to find its way across the country during its annual migration. Reported in Nature, this is the first invertebrate known to use the stars for long-distance travel.
Every spring, billions of Bogong moths (Agrotis infusa) escape the blistering heat of southeast Australia by migrating up to 1,000 km to a place they have never been to before – a cluster of cool caves in the Australian Alps. There, they lie dormant, until the autumn, when they make the return journey to their breeding ground to reproduce and then die.
How they get there and back has been something of a mystery. “Our previous research showed that the moths use the Earth’s magnetic field, but it also showed that they must be using some sort of visual cue,” says Andrea Adden from the Francis Crick Institute who took part in the study.
Looking at the sky, where the adult moths emerge, the most obvious cue was the Milky Way. “It’s this bright band, with a gradient to it, that expands across the entire sky.”
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To determine if the stars are involved, the researchers tested moths in a purpose-built flight simulator kitted out with the Milky Way projected onto a screen inside it.
Presented with natural starry skies, the moths consistently flew in the correct migratory direction for the season – southwards in spring, and northwards in autumn. When the projected image was rotated 180 degrees, the moths reversed direction accordingly.
“This proves they are not just flying towards the brightest light or following a simple visual cue,” says Eric Warrant from Lund University. “They’re reading specific patterns in the night sky to determine a geographic direction, just like migratory birds do.”
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Credit: Australian Academy of Science
The only other invertebrate known to navigate using the stars is the dung beetle, but this is across short distances and lacks a purposeful direction. Individuals use starlit skies to roll their prized dung balls in a straight line away from the dung heap. Bogong moths, in contrast, use the same galaxy to guide their movements in a specific direction over hundreds of kilometres.
“It really is astonishing,” says Adden, who also tracked down the specific brain cells responsible for this ability, “but these won’t be the only moths to do this.” There are many species of migratory moth. Now, time will tell if they too navigate by the stars.
Find out more about the study: Flight simulator for moths reveals they navigate by starlight
Main image: Milky Way, Australia. Credit: Getty
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