In Australia, millions of newly hatched Bogong moths embark on an impressive journey twice a year. Each spring, they hatch from eggs in their breeding grounds in Australia’s southeast and fly up to 1,000 kilometers (621 miles) further southward to spend a few months in the cool caves of the Australian Alps — a place they’ve never visited before. Then come fall, the same individuals fly north back to their breeding grounds, where they mate, lay eggs and die. A new study has found that the moths, with no parents to guide them, rely on bright stars and the Milky Way visible in the night sky to aid their migrations.
Researchers had previously shown the Bogong moths (Agrotis infusa) use Earth’s magnetic field and some unknown, natural visual landmarks to reach the Alps. They suspected that stars or the moon might act as those visual cues.
To test their theory, the same researchers in the recent study captured migrating Bogong moths enroute to the Alps and transferred them to a small enclosure with no magnetic field in a lab. They then projected the night sky onto the enclosure’s ceiling and recorded the moths’ flight directions.
The team found that when they projected the natural starry sky and the Milky Way as is, the moths flew in their correct migratory directions. When the researchers rotated the star patterns, the moths turned accordingly. When the star map was scrambled, and the Milky Way and constellation patterns were lost, the moths became disoriented.
“This proves they are not just flying towards the brightest light or following a simple visual cue,” study co-author Eric Warrant from Lund University, Sweden, said in a statement. “They’re reading specific patterns in the night sky to determine a geographic direction, just like migratory birds do.”
The researchers also recorded neural activity in the moths and found that specific neurons in regions of their brains known to handle navigation lit up in response to rotations of the night sky.
“This is a truly remarkable insect,” Warrant told The Guardian. “It can make this incredible journey with a tiny brain and a small nervous system, and do it in two directions.”
When the skies were cloudy and the night sky was obscured, the moths could still navigate in the correct migratory direction, “strongly suggesting reliance on the only known remaining compass cue—the Earth’s magnetic field,” the authors write.
Pauline Fleischmann, who studies insect navigation at the University of Oldenburg, Germany, but wasn’t involved in the study, told NPR that the findings show that for insects, “their world is probably much more filled with information than humans usually assume.”
Populations of Bogong moths, found only in Australia, have declined in the past decades, and the species has been listed as endangered on the IUCN Red list since 2021.
Banner image: Australia’s iconic Bogong moth. Image courtesy of Ajay Narendra, Macquarie University.
This story first appeared on Mongabay
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