Decades ago, spring in Australia meant lifting a towel or opening a curtain to a surprised moth or two fluttering out, as billions of bogong moths migrated across vast swaths of the country’s southeast.
But since the 1980s, the bogong moth population has declined drastically because of the increased use of insecticides, habitat destruction and the proliferation of artificial lighting. Bad droughts in 2017 and 2018 reduced the insect’s population by about 99.5 percent. Many Australians were left wondering whether the moths would ever return.
This year, the swarms are back and scientists are rejoicing.
Droves of bogong moths are once again completing the journey from the warm inland plains to estivate, a form of dormancy, in the cooler alpine areas of the country’s east between September and November. The 1.8-inch brown moths, with a distinctive black stripe and two silver spots on both wings, use the earth’s magnetic fields and light from the night sky to orient themselves. The moths return inland to breed during March and April.
Over the past few days, videos showing people being startled as moths emerge from drying towels have gone viral, as has footage of moths swarming on walls, gathering on windows or hitching rides in car trunks.
Marissa Parrott, a senior conservation biologist at Zoos Victoria, said there had been tears and happy dances at her office as citizen scientists logged their sightings on Moth Tracker, a website she co-leads. “My cheeks hurt because I’ve been smiling so much,” she said.
“Seeing the bogong moths come back so well this year gives us all amazing hope that even though they’ve been knocked down due to those rough conditions in the past, that they can be resilient and they can bounce back.”
Since the start of September, the Moth Tracker team has received 4,000 submissions. They have analyzed more than 1,850 of those, confirming more than 1,600 as bogong moths.
In 2024, which Dr. Parrott said was the previous best year on record, there were more than 1,950 submissions with 1,089 verified bogong moths. The moths are found across most of Australia, but the main migration occurs in the country’s southeast.
Dr. Parrott said the population has taken time to recover following the drought. This year has been wetter and cooler in parts of the country, creating ideal conditions for the moths.
“This year, I think they’ve gotten up to that more critical mass where the population is a lot healthier,” she said.
The moth migration has caused chaos in the past. In 2000, they wreaked havoc at the closing ceremony of the Sydney Olympics, when weather forecasters initially mistook a swarm for a rain cloud (the insects had been drawn to the stadium’s bright lights). The moths have also unsettled tennis superstars at the Australian Open, and forced Australia’s Parliament House to change its lighting to keep the migrating moths on track.
The moths play a vital role in ecosystems in Australia, acting as pollinators and as a food source for animals — including the country’s only hibernating marsupial, the mountain pygmy-possum. The insects also hold cultural significance for Indigenous Australians.
Challenge not over yet
Stephanie Helm, owner of The Vintner’s Daughter, a vineyard in the state of New South Wales, first spotted a bogong moth when she was pulling up the blinds on Sunday.
Since then, her family has found the moths in the house, and all over their cherry blossom trees and trampoline.
“I’m feeling very, very special to have so many feeding outside my door,” she said.
Ms. Helm added that the region had experienced a “pretty rough run in the last few years” including wildfires, droughts, storms and hail. She said she had also noticed the disappearance of other insects.
“To see them come back just makes people feel like maybe things are getting back to normal,” she said of the moths.
The insects hold special significance for Ms. Helm’s family. Her father studied bogong moths decades ago for the country’s science agency and passed his curiosity on to his children.
Eleanor Drinkwater, an entomologist at Western Sydney University who is involved in Bogong Watch, another citizen-scientist project, said that while it was great to see the moths return in such large numbers this year, the future was still uncertain.
For example, climate change could affect the cool alpine refuge that the moths seek each year, she said. And even slight temperature changes have been shown to alter the moths’ behavior in lab settings, she added.
“It’s still important that we’re still very focused on conserving the species,” Dr. Drinkwater added.
Ms. Parrott, the conservation biologist, called for protection of the moths’ breeding grounds, the planting of native flora along their migration route and a reduction of bright lights.
“They still need a lot of help and they still face some serious battles,” she added.
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