The reason for NSW’s bogong moth invasion and how to help
Millions of bogong moths have become lost in the bright lights of the city after being blown off course during their yearly migration – but experts say the swarm is great news for the environment
READING LEVEL: GREEN
Kids weren’t the only ones with school holiday travel plans, as Sydney and parts of New South Wales were invaded by swarms of endangered bogong moths over the past fortnight.
For weeks, millions of moths have fluttered around NSW, finding their way into every single nook and cranny imaginable.
What’s behind this sudden, almost biblical influx of moths across the state, that some have dubbed the “mothpocalypse*”?
Insect expert Professor Dieter Hochuli from the University of Sydney said moth migrations were a natural phenomenon, but there was one factor making things a little different this year.
“This is one of the great animal migrations of the world,” Prof Hochuli said.
THE GREAT BOGONG MIGRATION
Every spring, an estimated four billion Bogong moths breed in central, inland NSW, before heading south to a cooler climate for the summer.
“When spring hits, they navigate using the stars and magnetic fields to migrate down south to the Australian Alps,” Prof Hochuli said.
Their treacherous journey takes them across southern NSW, Canberra, and Victoria, where they will spend the warmer months in alpine caves. There they are a vital food source for the critically endangered mountain pygmy possum.
With bogong numbers declining in recent years, the future of the mountain pygmy possum has become even more uncertain.
BOGONGS BLOWN OFF COURSE
This year, while it’s been great to see such large numbers of bogong moths make their yearly migration, unusually strong westerly winds blew the insects severely off course.
Unfortunately they landed in the middle of suburbia – and according to Prof Hochuli, they really don’t want to be here.
Once they accidentally besieged the city, major infrastructure* made their orientation problem even worse.
“Because they navigate using light from the moon and stars, city lights are essentially like someone hacking into your Google Maps and spinning it around,” Prof Hochuli said. “It sends them confusing messages and they get stranded.”
‘MOTHPOCALYPSE’
The sheer number of stranded moths has caused a viral stir online, with unbelievable scenes of hundreds, sometimes thousands of moths in people’s homes, gardens, and even washing up on eastern coastlines.
In one viral video, a Sydney content creator filmed himself walking along Jibbon Beach in Bundeena, NSW, where he initially assumed the dark patterns on the sand were just washed-up seaweed.
However, upon closer inspection, he realised it was actually thousands of dead moths washed up on the shore.
Westerly winds have been blowing the exhausted insects right off the coast, and because they can’t land on water, thousands have dropped into the ocean and eventually washed ashore.
Scores of viewers have taken to the comment section of viral videos to share that the moths are driving them mad.
“OMG I feel sick, why are you so calm?” one person commented on a viral video of thousands of moths swarming a man on the NSW South Coast.
“That’s how I imagine HELL,” wrote another.
However, despite some expressions of disgust, many defended the poor creatures.
“This is so sad, the moths were just resting in the dark and would have moved on sundown,” one person commented.
“These moths are a critical food source for the pygmy possums,” another wrote.
VITAL FOR THE ECOSYSTEM
While moth expert Prof Hochuli said many people were finding the moth influx annoying, the creatures were actually an incredibly important part of our ecosystem*.
And their significance isn’t limited to NSW. When the moths eventually reach Victoria’s high country, they are a vital food source for that state’s critically endangered* pygmy-possums too.
“And down here in the city, birds and lizards are having a field day, and they’re keeping plenty of domestic cats entertained,” Prof Hochuli said.
The insect expert has urged people not to kill the moths and asked impacted households to accept a bit of temporary irritation for the greater good of the ecosystem.
“Overwhelmingly, most of these moths will die before they can reproduce, that’s why it’s completely normal to see dead moths around your house,” he said.
While some species of moths chew holes in clothes, bogongs don’t, which means there’s no threat to your wardrobe.
“They are not going to eat your clothes or ruin your gardens; the moths that destroy your laundry are a completely different species,” Prof Hochuli said.
“The reason you are finding them mushed up in your laundry or in the nooks and crannies of your house is just basic biology*: they are desperately looking for dark, tight crevices* to hide in during the day, so they don’t get eaten.”
Prof Hochuli’s final piece of advice was simple: just wait it out.
“They will either die off or move on in a matter of days or weeks,” he said.
If they are really bothering you, taking them outside is the best option – just gently sweep them into a dustpan or place a container over them and slide a piece of paper underneath so you can transport them outdoors and release them.
“There are plenty of things to worry about in the modern world, but bogong moths aren’t one of them,” he laughed.
“We’re actually getting a first-hand look at some amazing animals trying to complete an incredible journey.”
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GLOSSARY
- mothpocalypse: a play on the words “moth” and “apocalypse” or end of the world
- infrastructure: structures for the running of society, such as street lights
- ecosystem: the way different creatures interact with each other and the weather and landscape
- critically endangered: facing an extremely high risk of extinction in the wild
- biology: animal nature, the moths are instinctively looking for dark places to hide when they sleep so they don’t get eaten
- crevices: narrow cracks
EXTRA READING
Can you help find our bogongs?
Where have all the Bogong moths gone?
Twelve tiny possum babies born
QUICK QUIZ
1. What drives the great yearly migration of Bogong moths?
2. What sent the moths off course this year?
3. How do Bogong moths navigate during their yearly migration?
4. Bogong moths are an important source of food for which critically endangered species?
5. What should you do if you don’t like having Bogongs in your home?
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CLASSROOM ACTIVITIES
1. Five things you should know
Create a fact sheet titled “Five things you should know about Bogong moths” to inform the public about these important insects. Because you can only include five facts, you will need to think carefully about which parts of this news story are the most interesting or important. The five facts you include should help people understand what is happening, what they should do, and why they should try to be tolerant of the creatures.
Time: allow 30 minutes to complete this activity
Curriculum Links: English; Science
2. Extension
Research to find some other examples of animals that migrate. Choose one species to explore more deeply and write a short summary to describe their migration habits.
Time: allow 30 minutes to complete this activity
Curriculum Links: English; Science
VCOP ACTIVITY
What happens next?
Imagine the full story turns out to be in three parts and this article is only Part One. Think about what the rest of the story could be and write the next two parts that tell the rest of this story.
Time: allow 30 minutes to complete this activity
Curriculum Links: English, Critical and Creative Thinking