Arsenic threat: Bogong Moth gets the ‘all clear’

Posted on September 5, 2011

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They made world headlines as intruders at the Sydney Olympics – and attacked Parliament House during a visit by former US President, George Bush….

Ms Love collecting moths at Mt Barrow

They then gained additional notoriety when found to have arsenic levels that appeared to threaten endangered Alpine wildlife – and possibly even humans.

Now, after a three-year study, Australia’s Bogong Moth is ‘off the hook’ as far as controversial arsenic poisoning fears are concerned.

The La Trobe University study found no evidence that concentrations of arsenic in these iconic creatures has been caused by human intervention in the environment, nor that it represents a threat to wildlife or human health.

The moths swarm in great numbers over large distances in Eastern Australia to spend summer in the Alps, sometimes causing considerable havoc on their journeys.  They are also culturally significant to many Indigenous groups, serving as a source of food.

The study was carried out by PhD researcher Pettina Love, of the Bundjalung Nation Aboriginal community and child of a member of the Stolen Generation. She graduated recently at La Trobe’s Albury-Wodonga campus. 

Dr Love says because the moth is at the bottom of the food web and an important source of protein and fat, the arsenic contamination was feared to put at risk native Alpine animals such as endangered pygmy possums, small marsupial antechinuses and birds.

‘Sub-lethal quantities of arsenic can cause cancer, mutation and birth defects. Due to its cumulative nature, continued exposure to small sub-lethal amounts may ultimately cause death,’ she says.

However these concerns, voiced over the past decade, were based on limited data and the assumption that the source of the arsenic was caused by human changes to the environment.

For example smoke stacks in cities put an enormous amount of arsenic into the atmosphere. It was thought that during their flights, moths might pick this up on their wings.

Their larvae, while in the soil, might have been sprayed by agricultural chemicals and the arsenic introduced that way. Or, as Australian soil is naturally high in arsenic, it may have been a natural background level not noticed before.

Hence her three-year PhD study into the moths, supported by a $110,000 ARC Discovery Indigenous Researchers Development grant.

Dr Love worked with members of Aboriginal communities to collect Bogong Moths from various regions. Chemical tests for arsenic were conducted on more than 800 moths, followed by detailed statistical analysis and the establishment of valuable base-line data.

Natural background levels

‘The arsenic concentrations we detected formed a single distribution consistent with natural, or background, levels. ‘No significant differences in arsenic concentration were found between Bogong Moths from different locations or different years – nor between migrating moths or those resting in the Alps during summer.

‘Our findings suggest that the source of arsenic is not related to any environmental changes brought about by humans. ‘And the concentrations of arsenic, plus seven other chemicals found in Bogong Moths in my study, pose no risk to people.’ (Arsenic is linked to companion chemicals like lead, caesium or magnesium which can provide clues to its original source.)

‘The concentrations I found is comparable to other food in the Australian diet,’ says Dr Love.  ‘And there is no evidence that the concentration of arsenic poses a risk to Mountain Pygmy Possums.’

Dr Love says the Bogong Moth study was an appealing project, resonating with her personal background.  ‘It acknowledged the interest many Indigenous people have in the conservation of this Indigenous icon.

‘It dealt with environmental and health issues that potentially impinged on the cultural traditions of many Indigenous groups who have a connection with the moth and its habitats. 

 ‘Traditionally many groups went to Alpine regions and conducted ceremonies while supported by a moth diet. A Bogong Moth Festival is still held in Albury-Wodonga each year.’

Some people, says Dr Love, still eat the moth. ‘The favoured method of cooking is BBQ. Opinions vary about the taste. Some people report a peanut butter flavour and others saying they have a sweet after-taste like nectar.’

Arsenic was first discovered in the Bogong Moth about ten years ago. It generated debate and research among scientists, and some concern in the wider community.
Dr Love says there were ethical expectations and cultural obligations she had to meet to conduct her research. 

‘When working with fellow members of the Aboriginal Community I had to appropriately communicate the intent, progress and results of my research,’ she says.

Mating flights

Dr Love examines moths in her laboratory

Her research supervisor was Dr Susan Lawler, Head of Environmental Management and Ecology and winner of an Australian Learning and Teaching Council Citation for outstanding contribution to student learning.

Dr Lawler says Bogong Moths start their life cycle as cutworm larvae. They are found from Queensland to southern Victoria, and across to Adelaide. 

They are agricultural pests in pastures because they feed on plants. When hatched, they become a moth and fly to the mountains where they hide in rock crevices. No one really knows why. Possibly these are mating flights.’

Studying the moths is extremely difficult, says Dr Lawler. Their migration routes vary widely, journeys can be a 1,000 kms or more, and the numbers that show up in the mountains change dramatically from year to year.

However, the reason they often cause problems at Parliament House in Canberra – which is located on a high-traffic moth route to the Alps – or at major sporting events like the Olympics and the Australian Open tennis in Melbourne is simple: these places are extremely well lit, and moths gravitate to bright light.

‘We recently found a population from Tasmania coming across on the ferry to Melbourne. In the morning they were fluttering against our porthole window, and when we went up on deck we found they were all over the boat, settling into crevices as if they were on top of the mountain

Listen to the Dr Lawler being interviewed by Robyn Williams on the ABC Science Show.