Citizen science to help the Bogong Moth and Mountain Pygmy-possum

By Dr Marissa L. Parrott, Estelle Van Hoeydonck, and Hannah Sly
Zoos Victoria

The Bogong Moth (Agrotis infusa) is an Australian icon. While it is small, around 25-35 mm long, and weighing an average of 0.33 g (less than a Tic Tac!), the species manages an epic annual migration. The moths travel up to 1,000 km from their breeding grounds in southern Queensland, NSW, ACT, western Victoria, and South Australia, to the alpine zones of Victoria and New South Wales every spring.^1,2 They make an equally impressive migration back to their breeding grounds each autumn to lay their eggs, feasting on native flower nectar and pollinating plants along their route.

However, a collapse of the Bogong Moth population by an estimated 99.5% has placed them – and the alpine species which rely on them, like the Critically Endangered Mountain Pygmy-possum (Burramys parvus) – in peril.³

Prior to 2017, there were estimated to be around 4 billion moths migrating annually, with people recalling swarms of these little moths blocking out the stars and moon when they travelled overhead.² Bogong Moths spend their summers in cool boulder-fields, and dark caves, where they nestle over each other like tiles on a roof. There can be up to 17,000 moths per square metre lining cave walls.⁴ 

The moths use a combination of visual landmarks, light on the horizon, and Earth’s magnetic field to navigate on their migration.⁵ Previously, such nuanced navigation and sophisticated migratory abilities were thought to occur only in vertebrates, but a handful of invertebrates like the Bogong Moth, and internationally the Deaths-head Hawkmoth (Acherontia atropos), have proven invertebrates are just as remarkable.⁶

The annual arrival of the Bogong Moths brings the second biggest influx of nutrients into the alpine zone, beaten only by the sun.¹ The nutrition from these magnificent moths nourishes everything in the ecosystem, via their consumption by predators.¹ The arrival of the moths is also culturally important: for thousands of years, First Nations people travelled to the alpine zones to meet, celebrate and feast on the bountiful moths.⁷

What went wrong?

There has been a long-term decline in Bogong Moth numbers since around 1980, due to threats from agricultural practices including land clearing for crops, irrigation (a key issue as moth eggs and caterpillars live on/under-ground), and increased use of damaging insecticides. Further threats include increased light pollution that disrupts the moth’s migration, direct poisoning of moths when they are drawn away from their migration by the bright lights (e.g., to buildings and city centres), destruction of habitat and flowering food plants on their migration routes, introduced predators, and a warming/drying climate.²

There was a catastrophic collapse of the Bogong Moth population in 2017 and 2018, which was likely due to the widespread and devastating drought across south-eastern Australia in their breeding grounds. In some regions, this was the worst drought in recorded history.

In December 2021, the Bogong Moth was added to the International Union for Conservation of Nature (IUCN) Endangered species list.⁸

The catastrophic decline of the Bogong Moth is not only devastating for the moth itself, but affects a wide range of species and ecosystems. One species whose survival is closely intertwined with the moth is the Mountain Pygmy-possum. There are likely fewer than 2,000 of these tiny possums left in the world.

Bogong Moths are a rich source of fats, protein, vitamins, and nutrients, and are a critical food that Mountain Pygmy-possums consume in spring after they wake from their annual winter hibernation, before breeding and raising their young.⁹ 

Work by members of the Mountain Pygmy-possum Victorian State Recovery Team showed that in the worst years, females were often underweight, and could not produce enough milk for their young. Over 50% of female Mountain Pygmy-possums in monitored Victorian populations lost their full litters, and in the largest and worst affected population, 95% of females lost all their young. Post-mortem analyses did not show any disease, illness or injury. They simply starved.¹⁰

New programs to protect and recover moths and possums

The Recovery Team and partners developed and expanded programs to investigate the issue and further protect the possums and moths.¹⁰ At Zoos Victoria, we commenced a new program in 2019 to develop a supplementary food source from commercially available ingredients for use in emergencies: “Bogong Bikkies”.¹¹ Using previous analyses of Bogong Moths, we worked with world experts in veterinary nutrition to develop the bikkies – nutritionally suitable baked biscuits for Mountain Pygmy-possums, and other species that live alongside them.¹¹

We trialled the bikkies with the Mountain Pygmy-possums in our care at Healesville Sanctuary to show they were safe, palatable and effective. With partners, Parks Victoria, we then trialled the food with a wild population of Mountain Pygmy-possums to ensure the food, and appropriate ways to deliver the food, were all ready in case of emergencies such as food shortages or bushfires.

Thankfully, the food has not been needed yet in Victoria. However, we have been very proud to help our partners in the NSW Saving Our Species team, who used the bikkies to sustain wild possum populations in the Northern Kosciuszko National Park following the devastating 2019/20 Black Summer bushfires.¹² As a result, the possum populations successfully bred and raised their young.

But how do we learn more about Bogong Moths and how best to help them? There are still numerous questions about their breeding grounds, migration routes, areas of rest or foraging, and potential pitfalls and threats along their journey. Thus, in 2019, we developed a new citizen science program, Moth Tracker.¹³

The program aims are four-fold:

1. to gain important knowledge on the migration, annual trends and numbers of Bogong Moths;
2. to investigate key threats to the moths and determine where they may be drawn away from their migration;
3. to provide early indications of moth numbers to aid planning to assist support of Mountain Pygmy-possums in times of food shortage; and
4. to raise awareness of the plight of the Bogong Moth and Mountain Pygmy-possum and empower the community to help.

Zoos Victoria launched Moth Tracker as a free-to-use citizen science webpage, hosted on the State Wide Integrated Flora and Fauna Teams’ (SWIFFT) website. If people see what they think is a Bogong Moth, they can take a photo, upload it to the Moth Tracker website¹⁴ with the time, number, and location of the moth(s) and Zoos Victoria’s moth team will confirm the species and add it to our live interactive map. This species verification ensures the correct data and species is recorded. Members of the public can then check their sighting on the map after a couple of days to see if it was a verified Bogong Moth.

How is Moth Tracker tracking?

With the Bogong Moth traversing such a wide area of Australia, using people power and citizen science can help fill the knowledge gaps on population trends and migration. Now completing its fifth year, Moth Tracker continues to grow, with the highest number of sightings submitted in spring 2023-autumn 2024. Over 1,000 sightings were submitted this season, with a total of 5,018 photos analysed across the life of the program from all Australian states and territories.

In consultation with Bogong Moth research partners, we have also engaged with communities in areas of interest and gathered new data from key breeding areas and states including Western Australia and Tasmania, where Bogong Moths occur, but less is known of their distribution.

While Bogong Moth numbers have increased since the collapse of 2017 and 2018, their numbers remain dangerously low, and the moths have failed to return to some long-term survey sites.2 The number of verified Bogong Moths, and the number of swarms or groups of moths, also fluctuates widely between years, following the trends seen by our partners at long-term sites. It appears the La Niña weather pattern assisted numbers in 2022-2023,¹⁵ but numbers in 2023-2024 were lower and we hold grave concerns for future years under a changing climate.

Early research of community recognition of Bogong Moths and Mountain Pygmy-possums showed a statistically significant increase in the correct identification of the species after Zoos Victoria’s campaign.¹³ However, many people struggle to identify the moths, and mistakenly believe that Bogong Moths are very large, even up to the size of a human hand. Therefore, we have focused on education about the size and appearance of Bogong Moths.

In the early years of Moth Tracker, around 30% of spring-time submissions were verified as Bogong Moths. The rest could not be verified from the photo provided, or were actually other species like the larger Emperor Gum (Opodiphthera eucalypti), Southern Old Lady (Dasypodia selenophora), and Rain Moth (Abantiades atripalpis). In the past two years, however, there has been an increase to 50% of spring-time submissions verified as Bogong Moths.

Media interest in the program and species has remained very high with annual media articles and stories calling for action. Over the past two years, Zoos Victoria has also provided asset packs to over 60 partner organisations to encourage participation in Moth Tracker. First Nations groups, environmental and government partners, community groups and more, have shared Moth Tracker posts, reaching millions of people.

Data from Moth Tracker has been added to Australia’s Atlas of Living Australia,¹⁶ significantly increasing the data available on the species, and has also been used by multiple university and other research programs. Moth Tracker is also a component of an exciting Bogong Moth Australian Research Council Industry Fellowship program at the University of Western Sydney, with partners including Lund University and Invertebrates Australia.¹⁷

Data has also been submitted as part of the current Australian Government’s review into listing the species as Endangered in Australia. While the Bogong Moth met key criteria and was added to the IUCN’s Endangered species listing in 2021, it is not yet listed nationally.⁸ However, data from multiple scientists and programs have been submitted, which should also trigger an Endangered species listing and additional protection under Australia’s Environment Protection and Biodiversity Conservation Act.

How can you help?

This spring, we invite you to join the search for the small but mighty Bogong Moths during their migration and add suspected sightings to the Moth Tracker website. People often spot them around their homes and gardens! To identify a Bogong Moth, look for the dark stripe on their wings, accompanied by a circular spot and a kidney-shaped spot on either end.

Additional ways to help Bogong Moths include simple measures such as planting native flowering plants in gardens, not using insecticides, and turning off unnecessary outdoor lights at night.¹⁸

The ability to help and track species like the Bogong Moth reminds all of us how truly amazing our moths and other insects are. When we learn about these species, we care about them. When we care about them, we act to protect them for the future. Will you join us?

Visit: zoo.org.au/mothtracker

References:

1. Green, K. (2011). The transport of nutrients and energy into the Australian Snowy Mountains by migrating bogong moths Agrotis infusa. Austral Ecology, 36(1), 25–34. doi.org/10.1111/j.1442-9993.2010.02109.x
2. Green, K., et al. (2020). Australian Bogong moths Agrotis infusa (Lepidoptera: Noctuidae), 1951–2020: decline and crash. Austral Entomology, 60(1), 66–81. doi.org/10.1111/aen.12517
   
3. Sadler, H. (2021, December 17). “A 99.5% decline”: what caused Australia’s bogong moth catastrophe? The Guardian. theguardian.com/environment/2021/dec/18/a-995-decline-what-caused-australias-bogong-moth-catastrophe
   
4. IFB Common. (1954). A study of the ecology of the adult bogong moth, Agrotis Infusa (Boisd) (Lepidoptera: Noctuidae), with special reference to its behaviour during migration and aestivation. Australian Journal of Zoology, 2(2), 223. doi.org/10.1071/zo9540223
   
5. Warrant, E., et al. (2016). The Australian Bogong Moth Agrotis infusa: A Long-Distance Nocturnal Navigator. Frontiers in Behavioral Neuroscience, 10(77). doi.org/10.3389/fnbeh.2016.00077
   
6. Menz, M., et al. (2022). Individual tracking reveals long-distance flight-path control in a nocturnally migrating moth. Science, 377(6607), 764–768. doi.org/10.1126/science.abn1663
   
7. Flood, J. (1980). The moth hunters: Aboriginal prehistory of the Australian Alps. Canberra Australian Institute of Aboriginal Studies. ISBN 978-0391009943.
8. Warrant, E.J. et al. (2021). Agrotis infusa. The IUCN Red List of Threatened Species 2021. dx.doi.org/10.2305/IUCN.UK.2021-3.RLTS.T190513532A196183274.en. Accessed on 13 June 2024.
9. Gibson, R.K. et al. (2018). Susceptibility to climate change via effects on food resources: the feeding ecology of the endangered mountain pygmy-possum (Burramys parvus). Wildlife Research, 45(6), 539. doi.org/10.1071/wr17186
   
10. DEECA. (2019). Mountain Pygmy-possum Operational Contingency Plan. Department of Energy, Environment and Climate Action. Victorian State Government. environment.vic.gov.au/__data/assets/pdf_file/0028/441559/MPP-Operational-Contingency-Plan-2019-20.pdf. Accessed on 13 June 2024.
11. Parrott, M. L. (2021). Emergency Response to Australia’s Black Summer 2019–2020: The Role of a Zoo-Based Conservation Organisation in Wildlife Triage, Rescue, and Resilience for the Future. Animals, 11(6), 1515. doi.org/10.3390/ani11061515
    
12. Parrott, M., & Davis, N. E. (2020, February 6). Looks like an ANZAC biscuit, tastes like a protein bar: Bogong Bikkies help mountain pygmy-possums after fire. The Conversation. theconversation.com/looks-like-an-anzac-biscuit-tastes-like-a-protein-bar-bogong-bikkies-help-mountain-pygmy-possums-after-fire-131045
    
13. Carruthers D, et al. (2020). Migrating moths and alpine possums: Mobilising community across Eastern Australia. IZE Journal, 18-25. izea.net/wp-content/uploads/2023/09/IZE-Journal-2020-FINAL.pdf
    
14. Moth Tracker: zoo.org.au/mothtracker
15. Carruthers, D. (2022, December 17). A flicker of hope: Bogong moths in 2022. Australian Conservation Foundation. acf.org.au/a-flicker-of-hope-bogong-moths-in-2022
    
16. Species: Agrotis infusa (Bogong Moth). Atlas of Living Australia. bie.ala.org.au/species/Agrotis_infusa
    
17. Western Sydney University. (2023). Western researcher secures $1 million in ARC funding for vital Bogong moth research. westernsydney.edu.au/newscentre/news_centre/more_news_stories/western_researcher_secures_$1_million_in_arc_funding_for_vital_bogong_moth_research. Accessed on 13 June 2024.
18. Lights off for the Bogong Moths. (2019, August 26). Zoos Victoria. zoo.org.au/healesville/whats-on/news/lights-off-for-the-bogong-moths