Do bogong moths steer by the stars?

A research project in Australia and Sweden is trying to understand how bogong moths perform incredible feats of navigation. Kate Prestt reports.

PhD scholar Jesse Wallace from the ANU Research School of Biology wears a face mask when he scrambles into a granite cave at Kosciusko National Park in search of the bogong moth, an iconic long-distance navigator even the military is keen to learn more about.

This insect that has a brain the size of a grain of rice is able to do this amazing navigational feat.

He manoeuvres himself into the tight confines to lie on a thick bed of dead bodies and excrement from successive generations of the moth to catch a glimpse of the hundreds of thousands that tile the blackened walls.

The bogong moth is famous for invading Canberra homes and Parliament House in spring when the bright lights divert them from their normal migratory route.

For generations Indigenous people would feast on bogong moths, from November to February. Every summer large numbers of Aborigines would gather in the highest mountains near the present site of Canberra at the peak of the migration towards the end of December.

These remarkable nocturnal navigators with a wingspan of 40–50 mm, smaller than most people think, are now in the spotlight as the world looks for smaller navigational technology.

For Australian and international researchers, the bogong moth represents a new and promising way to understand the sensory basis of nocturnal migration in insects.

Wallace’s study, a collaboration between ANU and the University of Lund, Sweden, looks at the genetics of the bogong moth and how, despite having no previous experience, they fly up to 1000 kilometres from breeding grounds in Queensland, New South Wales and Victoria to the Snowy Mountains, where they aestivate over summer.

The moths fly at night when visual compass cues can be unreliable and the moon varies in prominence; however, researchers believe the moths steer by the moon and the nightly movement of stars as well as the Earth’s magnetic field.

His biological research is supported by agencies that are interested in how creatures solve complex navigational tasks.

Wallace is being funded by an Australian Government Research Training Program Scholarship, along with funds from the European Research Council, the Australian Department of Defence and the United States Air Force Office of Scientific Research.

He is using several methods to find answers to his questions about how the moths navigate. “Initially, I looked into doing radio telemetry, but for a 200-milligram flying insect, radio tracking is very challenging, we don’t have the technology yet,” he says.

“I am now using a few molecular methods to hopefully answer how the moths can navigate thousands of kilometres to this very specific place in the mountains.”

His fieldwork took him on a road trip to visit breeding sites that zigzagged around New South Wales and Queensland.

“I got to go and see places I would otherwise have to wait to see until I was retired and had sold my house and traded it for a caravan,” he says.

“It was really interesting to get out and meet people and talk about the project in some beautiful areas.”

During summer Wallace hiked to caves dotted throughout the Snowy Mountains in search of the moths.

“I love hiking mountains every other day, but the main thing that motivates me is learning about nature and figuring out how this insect that has a brain the size of a grain of rice is able to do this amazing navigational feat, when humans are yet to figure out how to make robots do this.”

This year has not been good for the bogong moth, with fewer making it from the breeding grounds to the caves.

“We have seen far fewer caves being used by the moths this year and in the caves where they are, there are fewer moths,” he says.

“We think this is because it was quite a dry winter in 2017 in their breeding grounds so there was less food for them. But we still don’t know what is causing fewer moths. We’ll have to wait and see next year if there are more moths, assuming the weather is better.”  

In the next stage of his doctoral research, he hopes to involve citizen scientists from across the country to collect bogong specimens from their breeding grounds in Spring.

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