Birrigai Rock Shelter

Published by

Merrill Findlay

on

September 20, 2025

Location: Tidbinbilla Nature Reserve
Country: Ngunnawal
LGA: Australian Capital Territory
Region: Southern Tablelands
Website: https://www.tidbinbilla.act.gov.au/
Map below

People have been visiting Birrigai Rock Shelter, in what is now Tidbinbilla Nature Reserve, for at least 25,000 years. Many of these visits were to harvest and roast Bogong Moths, a seasonal source of deliciousness for local people. For perhaps millions of years, these moths have migrated to this and other rock shelters, caves, and cleavages in the Southern Tablelands and Alps to aestivate; and, like people, they have used the stars to find their way.

birrigai-rock-shelter-background-information Download

BUT HOW DO MIGRATING BOGONG MOTHS FIND THEIR WAY TO BIRRIGAI?

Dreyer, D., Adden, A., Chen, H. et al. Bogong moths use a stellar compass for long-distance navigation at night. Nature 643, 994–1000 (2025). https://doi.org/10.1038/s41586-025-09135-3

The question remains of what aspects of a moonless austral night sky might be useful as compass cues for Bogong moths. Humans^15,16 and birds^6,13,14 can use individual stars, or constellations of stars, as compass cues for distinguishing specific geographical directions, but it remains unclear how many of the brightest stars are discernible by the moth’s small compound eyes. However, the Milky Way—which, in the Southern Hemisphere, is a bright extended stripe of light that becomes brightest somewhere in the southern half of the sky^7,10—is very likely visible to Bogong moths³⁹, as also suggested by our physiological results (Fig. 4). Its shape and celestial position at any time of night are predictable from one night to the next throughout each migratory season, and its rotation around the South Celestial Pole over any single night retains the brightest parts of the Milky Way (including the Carina nebula) somewhere in the southern half of the sky, but not consistently due south. Exactly where the brightest parts are located depends on season and time of night and can vary from southeast (Figs. 2a and 3b) to almost due west (Fig. 3a). Thus, a simple phototactic mechanism, with Bogong moths orienting towards the brightest parts of the sky in spring and away from them in autumn, seems unlikely. Furthermore, the presence of a bright moon in different parts of the sky would severely disrupt such a mechanism. However, Bogong moths orient in their inherited migratory direction even when the moon is present (Fig. 2a,b).

s41586-025-09135-3 (1)Download

For more on bogong moths’ capacity for celestial navigation, see Eric Warrant’s article, Migrating bogong moths use the stars and Earth’s magnetic field to find ancestral summer caves each year, in The Conversation, 19 June, 2025.

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