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How Toxic Is Traditional Bush Tucker in the Alps?

moths with popcorn

Popcorn with Bogong moths (pop-moth) is hardly a “traditional” bush tucker recipe, but is it contaminated with arsenic?

By Susan Lawler & Pettina Love

Bogong moths are not only traditional bush tucker for indigenous people, but they are also important food for many alpine species. But does the discovery that they contain elevated levels of arsenic pose any real dangers to indigenous people or the high country ecosystem?

Bogong moths are best known for the problems they cause when they arrive in our cities in large numbers. They interrupted the Sydney Olympics and attacked Parliament House during a visit by former US President, George Bush. These incidents occur because the moths migrate in large numbers at certain times of the year and are attracted to lights. Any well-lit building in the path of their migration will become inundated with moths for several days.

Where do the moths come from, and where are they going? Bogong moths lay their eggs in soil in the lowlands of eastern Australia, from Queensland to South Australia. They prefer the dark, self-mulching soils that are also used for agriculture. This means that Bogong moths are pests as soon as they hatch because the larval form feeds on the roots of plants, some of which are our crops. At this stage they are known to farmers as cutworms.

The larvae form a cocoon under the soil and undergo another transformation into the adult moth. The adults hatch in the spring and soon afterward begin their long migration, during which they fly to the mountains in Victoria and New South Wales. The moths are heading for the highest part of the Australian alps, where they push into crevices between the rocks above the tree line. The Bogong moths then spend the summer hiding among the boulder fields in the mountains. On warm nights, at dusk, they emerge and fly around in large enough numbers to darken the skies. When autumn comes they fly back to the lowlands to deposit their eggs in the soil.

Nobody really knows why the moths choose to congregate in the mountains every summer, but many animals benefit from this behaviour because the moths make a high quality meal. Their bodies are only 3 cm long but they are full of protein and fat. Crows, currawongs, bush rats, antechinus and mountain pygmy possums feast on the bounty provided by the moth migration. But they are not the only ones – people eat moths, too.

Traditionally, many groups of indigenous Australians would travel to the alpine regions where they conducted ceremonies in the summer. The abundance of the Bogong moths meant that there was plenty to eat even when many people gathered for an extended period. A Bogong moth festival, now called Ngan-Girra, is still held in Albury-Wodonga each year.

Bogong moths gained notoriety a decade ago when it was found that they contain elevated levels of arsenic. This created concern about the endangered mountain pygmy possum, which relies on them for food. Indeed, the whole food chain could be affected if the moths are bringing arsenic into the pristine alpine ecosystem. People might be affected, too.

Arsenic can cause cancer, genetic mutations and birth defects. Due to its cumulative nature, continued exposure to small sub-lethal amounts may ultimately cause death. With Bogong moths at the bottom of the food chain and people and possums at the top, there was cause for concern.

We decided to collect Bogong moths from as many localities as possible and carefully quantified the amount of arsenic within each population. The goal was to identify the source of the arsenic so that it could be eliminated or managed.

Our question was: where is the arsenic coming from? It sounds like a straightforward research question, but when thinking about the potential sources of arsenic we had to address two types of sources. In the first place, where, in a physical sense, was the arsenic coming from? And secondly what, in a practical sense, was producing the arsenic?

On the one hand, if some populations of moths had more arsenic than others, this could tell us to look for the arsenic in a limited geographical area. On the other hand, the presence of other chemicals in addition to the arsenic could tell us what industrial or human process might be the culprit. For example, the chemical “signature” could be used to tell if the arsenic came from industrial smoke stacks or agricultural chemicals. But since Australian soils are naturally high in arsenic it is possible that the source might not be due to human activities at all.

The first step was to collect moths from as many locations as possible. In many cases these populations were located in national parks, meaning that permits were required because all scientists must follow government regulations regarding the collection of native species.

But not all scientists are in the habit of asking for Permission to Enter Country. This is an Aboriginal custom that alerts people in an indigenous community that someone is going to enter their territory. Due to Pettina’s membership within the Aboriginal community, and because she was doing research on an issue important to the people concerned, she spent many months contacting local community groups to let them know that we would be collecting moths on their land, and why.

In many cases the Aboriginal communities offered to help collect the moths, and often Pettina was invited to give a presentation to their community group about our research. In this way we ensured that everyone in the community was aware of the project and had a chance to ask questions about the threat of arsenic in their traditional bush tucker.

It also meant that we had a list of people to contact once our research was completed to tell them about the results. At that time we did not know that we would be able to give them such good news at the end of 3 years.

We collected moths in New South Wales, Victoria and Tasmania, using a light trap to attract and collect the moths overnight. When the nights were warm and the air was still we could collect thousands in one night, but all too often the temperature dropped and the wind came up and the light trap would be empty in the morning. This often meant staying in a remote location for days until the weather was kind to us.

When Parliament House became covered with Bogong moths it seemed like a good idea to collect some in Canberra. This should have been a much easier field trip because the moths were all over walls of the building, just ripe for the picking. But Pettina discovered that collecting moths from Parliament House in the middle of the night led to discussions with security. However, when she explained that she just wanted a bag full of moths for her PhD, she found that the security guys knew all the best places to collect from.

We did not know that Bogong moths flew all the way to Tasmania until we began the research. Even though we knew they flew long distances, it seemed remarkable to imagine these tiny insects flying across the ocean. On the ferry, we noticed some moths fluttering against the porthole in our cabin, and in the morning we found thousands of Bogong moths hiding in crevices on deck. They had been attracted to the light and settled on the boat, which meant that some Bogong moths were actually hitching a ride across Bass Strait.

Eventually, we conducted chemical tests on more than 800 moths from 26 different locations. We analysed the arsenic levels but also looked for companion chemicals. Surprisingly, no significant differences were found between Bogong moths from different locations, from different years, or between migrating moths and those resting in the alps during summer. The arsenic concentrations detected formed a single distribution that was consistent with natural background levels.

Our findings suggest that the source of arsenic was not related to any environmental changes brought about by human intervention. Furthermore, the levels of arsenic and other chemicals detected in the moths pose no risk to people or other animals that eat them.

The levels of arsenic present in the Bogong moths were comparable to other food in the Australian diet. We have been able to contact community members and reassure them that their traditional bush tucker was not dangerous to them or the ecosystem.

Pettina’s PhD journey has resulted in a rare type of thesis that combines environmental management, community consultations and chemical analysis to discover that the Bogong moth is not contaminated with arsenic, and ultimately the conclusion that there is nothing to worry about. This is good news for the people and possums, and even better for the environment.

Pettina’s hard work was acknowledged when she received her PhD. The moths, the chemicals and the community helped her finally become Dr Love.

Susan Lawler is Head of the Department of Environmental Management and Ecology at La Trobe University’s Wodonga campus, and supervised PhD student Pettina Love, a member of the Bundjalung Nation, in this research.