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Australia's sky could change forever after winter ends
When Aussies look up into the sky at the end of winter, there will be a noticeable difference from what we saw a decade ago. Bogong moths used to migrate across Victoria, NSW, Queensland and South Australia in their billions, reportedly blocking out the moon, but in 2017 and 2018 their numbers crashed by 99.5 per cent.
Mortein once advertised its sprays could be used to kill bogong moths, but that advice was eventually removed after the species was listed as endangered in 2021. While the moths have been in steady decline since the 1980s, it was the sudden drop in numbers during the Millennium Drought that caused the average punter to take notice.
The situation has a leading conservation biologist 'extremely worried' both about the moth and the animals that depend on it as a food source, like the critically endangered mountain pygmy possum. Dr Marissa Parrott from Zoos Victoria said it's accurate to say 'within a generation, Australia has changed' as invertebrates vanish from the landscape.
'In Australia, with animals like the bogong moth, it becomes apparent things can go wrong very quickly,' she told Yahoo News.
For thousands of years, bongog moths have meant spring was here, and Christmas beetles were a sign of summer. These insects are wound up in memories from our childhoods, but today both are seldom seen.
'[Insect] numbers are all declining across time. But then you get those big events like a major drought, flood or bushfires and they can wipe out entire species,' Dr Parrott said.
'We're seeing that every day, that these animals are struggling, and we've probably lost far more invertebrates than we could ever even imagine… and it's only getting worse. We really need to change.'
Parrott notes the problem is a global one, with many referring to it as an 'intertebrate apocalypse'. Often, people don't realise the insects are gone until their crops stop being pollinated or the birds that eat insects suddenly vanish.
When it comes to bogong moths, the good news is that since 2018, there has been a trend towards recovery. But the species' future is far from secure.
Zoos Victoria's Moth Tracker project, an online platform where people around the country can report bogong moth sightings, was launched in 2019, and last year was its best season on record. Between September and December, there were 1,956 sightings, and 1,089 were verified by the expert team.
Some swarms (groups of over 100 moths) were even observed in 2024, something that hadn't been seen in years. "It was wonderful to see that again, but they're only one more drought from those numbers dropping right back low again. We need to have a long-term plan to protect and recover them," Parrott said.
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A bogong moth will live for around a year, with each dying after the autumn breeding season. The caterpillars live underground throughout the winter and then migrate up to 1,000km across Australia to alpine regions in the warmer months. Those that survive the feeding frenzy from native animals fly back across the country to their breeding ground to lay their own eggs.
'Each female can lay up to 2,000 eggs, so their numbers could bounce back quite quickly if we can protect them,' Parrott said.
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Earlier this week, a new study published in the journal Nature revealed bogong moths used constellations of stars and the Milky Way to navigate their migration routes. This upended a belief that moths simply flew towards the brightest light in the sky.
The team from Lund University, the Australian National University (ANU), and the University of South Australia compared their abilities to those of migratory birds.
Insects like bogong moths face multiple threats, including pesticides for agriculture, deforestation, climate change and light pollution. A 2017 study of select conservation areas in Germany found the insect biomass had dropped by 75 per cent in 27 years.
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