Figure 1: The Chestnut Tiger (Parantica sita) in Repulse Bay, prior to its capture. Photo courtesy: Yuet Fung LING.
On 21 December 2024, Dr Yuet Fung LING, a postdoctoral fellow at The University of Hong Kong's (HKU) School of Biological Sciences (SBS), made an unexpected discovery. While catching butterflies at Repulse Bay, he noticed a male Chestnut Tiger (Parantica sita) – a rare species in Hong Kong – with a sticker on its wing. Intriguingly, the tag bore Japanese characters and the date '18 Aug', revealing that this butterfly had been tagged and released in Fukushima four months earlier.
Dr Ling works with Professor Timothy BONEBRAKE and PhD candidate Miss Emily JONES in SBS. Together, they lead the Danaid Butterfly Research Hong Kong, a group dedicated to studying the seasonal movements of danaid butterflies in Hong Kong. By carefully placing URL-branded stickers on butterfly wings, the group tracks movements of species through public sightings and reports.
Through mutual colleagues, the research team managed to connect with butterfly markers, Mr Masayoshi SHIMIZU and Mr Hiroki TAKIZAWA in Japan to confirm the record. The adult butterfly was at least 124 days old and had travelled more than 3,000 km. This discovery sets a new distance record for the species and is only the third time a butterfly has been detected migrating from Japan to Hong Kong. The previous record, set in 2011, involved a Chestnut Tiger that flew an estimated 2,423 km and lived for 82 days.
On 18 August 2024, Mr Shimizu and Mr Takizawa spent the day placing stickers on the wings of the Chestnut Tiger butterfly at the Grandeco Ski Resort located in the Fukushima Prefecture of Japan. This species of butterfly is well-known for its long-distance migrations, and marking or tagging their wings provides valuable data about their movement, including how far they travel, the direction they take, and how long they survive. Over the course of the season, Mr Shimizu and Mr Takizawa spent six days at Grandeco, and managed to tag an impressive 481 butterflies.
'It's an astonishing feat. For a little insect like this to fly more than 3,000 km and do so for more than 100 days just shows the physiological capacity for these creatures,' noted Professor Timothy Bonebrake. 'The record also highlights how much is left to discover about these important migratory phenomena. To gather data to effectively conserve these migrations, we need more international collaboration like this and active participation from the public.'
After recording the butterfly, Dr Ling released it back into the wild. Whether Hong Kong is its final destination or just another stop in its journey remains a mystery.
Researchers are calling on the public to help unravel these mysteries. If you spot a butterfly with a sticker on its wings, report it to Danaid Butterfly Research Hong Kong. Every sighting brings us closer to understanding and protecting these amazing migratory species.
