Bogong moth influx across eastern Australia raises hopes after years of decline

Bogong moths are appearing in unusually visible numbers around homes in Sydney, Canberra and other parts of eastern Australia this spring, after years in which the migrating insects were scarce. In an account published on October 9, University of Sydney entomologist Caitlyn Forster described the resurgence along Australia's east coast. Conservation researchers welcome the sightings, but say it is too early to know whether they signal a lasting recovery.

The influx has brought moths into houses and other urban spaces in New South Wales, according to ABC News. Forster told the broadcaster that this season's numbers might be normal for the species, even though many people have not seen such gatherings for years. Zoos Victoria conservation biologist Marissa Parrott called it the best year in nearly a decade for the moths and said she hoped the apparent rebound would continue.

Why bogong moths are appearing near Sydney

Bogong moths travel long distances each spring toward cool mountain caves where they spend the summer. ABC News reported that the migration involves millions of moths over a stretch exceeding 1,000 kilometres. It said they breed in southern Queensland, northern New South Wales, western Victoria and parts of South Australia before heading toward the Victorian Alps. Their precise route remains largely unknown.

Forster wrote that two years of high rainfall had likely improved breeding and feeding conditions. Parrott separately told ABC News that increased rain and food in New South Wales and the ACT had helped bring moths in numbers not seen for a long time. Those are expert explanations for the sightings, rather than the result of a completed count establishing what happened across the whole population.

Does the influx mean the species is recovering?

The size of the recent decline explains why the sightings have drawn attention. Forster wrote that bogong moth numbers fell by 99% between 2017 and 2019. ABC News quoted Parrott estimating that 99.5% of the population had been lost, leaving the insects almost undetectable in recent years. These are attributed accounts of the earlier decline; neither report presents a new population census proving a sustained recovery in 2026.

Forster identified habitat destruction, drought and climate change among pressures on bogong moths, with light pollution another possible obstacle during migration. She also described a generational gap in what people regard as a normal abundance of insects: younger observers may have little memory of seasons with large moth gatherings. A conspicuous season can therefore be encouraging without, by itself, settling the longer-term trend.

The uncertainty matters for people seeing moths in cities as well as for conservation work. Forster told ABC News that the insects could disappear from urban areas within days or weeks, but she could not yet say how long they would remain. A cluster near a house may reflect weather or navigation conditions as well as the number of moths making the wider migration.

How researchers are tracking the migration

Researchers from Western Sydney University and Invertebrates Australia have marked moths with blue paint dots in the Blue Mountains and asked people to report sightings, ABC News reported. The marks are intended to help reveal the insects' distribution and flyways. The broadcaster also reported that researchers were monitoring 14,000 moths tagged on Mount Kosciuszko in February.

Online observations of untagged moths are being used to map where the insects appear, so researchers can compare sightings with weather patterns, according to ABC News. Parrott advised people to switch off unnecessary lights and upload moth photographs to Bogong Watch. Those records may help clarify where the moths are travelling while the causes and durability of this season's influx remain open questions.

Forster's October 9 article placed the moth sightings alongside another change Australians have noticed: Christmas beetles, once commonly seen in eastern Australia around December, have become rarer in recent decades. She said habitat loss may be a factor and that citizen observations help researchers because Australia has no formal Christmas beetle monitoring program. The two insects have different life histories, but both accounts show why recorded sightings matter when judging changes over time.