SINGAPORE - On the outskirts of the Singapore Botanic Gardens, one backyard quietly operates as a home, hospital and hospice for two of the Republic's most flamboyant swallowtail butterflies.
These are the common rose butterfly, which was
voted the national butterfly
in a 2015 contest held by Nature Society Singapore (NSS), and the common birdwing, the Republic's biggest butterfly.
Gardens that are initiated and run by members of the public, businesses and communities have been key to the resurgence of these delicate species, ecologists told The Straits Times.
In the "secret garden" off the Singapore Botanic Gardens, for example, butterfly conservationist Amy Tsang, who is in her mid-70s, and housekeeper Riza Burgos, 56, have created refuges for dozens of eggs and caterpillars of both species.
"None of us are trained in the field of butterfly conservation," said Ms Tsang, a retired civil servant. "But what we have in common is our deep love for creation's beautiful butterflies and a strong determination to see their survival in nature, for ourselves and the future generations to come."
The common rose butterfly was once considered vulnerable to extinction, with fewer than 1,000 mature individuals in 2008.
But in May 2024, the common rose butterfly's situation was determined to be less dire, and it was assessed as near threatened. This means the species is approaching, but has not yet reached, the threshold to be considered vulnerable.
The common birdwing still retains its locally vulnerable status.
Data by ecologist Anuj Jain, who helmed a 2021 study on the distribution of both species across the island, shows that at least 14 community-led or privately owned gardens have supported the butterflies' populations.
In the garden tended to by Ms Tsang and Ms Burgos, pupae dangle off the strangest of surfaces: a pillar, a plant rack and chopsticks ensconced in a mist net that deters hungry squirrels.
According to Ms Tsang's records in 2022, caring for common rose caterpillars indoors resulted in 75 per cent of them emerging as butterflies.
Together, Ms Tsang and Ms Burgos have raised generations of the common rose and common birdwing since December 2019, when the butterflies started breeding in the haven measuring some 200 sq m.
In the first half of 2025, an average of 11 common rose butterflies and 10 common birdwing butterflies emerged from cocoons in the garden each month.
"She's a butterfly whisperer," Ms Tsang said of Ms Burgos, showing a photograph of two common birdwings mating on the Filipina's hands, and another snapshot of the gardener feeding a slice of fruit to a butterfly handicapped by a deformed wing.
Ms Tsang credits their success to the dutchman's pipe (Aristolochia acuminata), an unassuming vine planted liberally around the garden.
While both butterfly species are native to Singapore, the plant they rely on is not. The dutchman's pipe, naturally found in Malaysia and Indonesia, is thought to have arrived on Singapore shores in the 20th century as an ornamental plant grown in parks and gardens.
Butterflies are notoriously fussy eaters, often feeding on one or two plant species, also known as their host plants. This makes them vulnerable to dying out once these plants vanish.
The natural host plant of both butterfly species is the native Aristolochia jackii, a close relative of the dutchman's pipe. But the native vine, found mainly in forests here, was last seen here in the wild in the 1930s.
This has resulted in an unusual situation where the two typically forest-dwelling butterflies are now critically dependent on urban plantings in parks and gardens, found a
2021 study
led by Dr Jain.
Both species are technically able to consume related plants from the genus Thottea.
But an experiment several years ago found that the common rose did not make it to adulthood when fed with Thottea praetermissa, while the common birdwing has not been documented consuming such host plants, Dr Jain added.
He said: "Therefore, we don't know of any wild butterfly populations using these host plants.
"An increase in population can therefore be attributed to targeted conservation efforts. This includes plantings by community members in private gardens, schools, and hospital campuses."
Inspired by Dr Jain's research, Ms Tsang and fellow members from the NSS' butterfly and insect group decided to give the butterflies a lifeline by spreading the dutchman's pipe near community gardens where these butterflies are known to breed.
The dutchman's pipe is believed to have fallen off planting palettes in part because of its plain appearance and the difficulty of cultivating the vine.
This made planting the climber something of an uphill journey, as it is not readily found in nurseries, said Ms Tsang.
She recalled how she and fellow volunteers even hiked into a tunnel in Clementi, where the plant had been spotted by hikers, to salvage the plant's wafer-thin seeds.
Through trial and error, Ms Burgos and Ms Tsang successfully propagated the plant species.
"We found that the dutchman's pipe likes to grow in places where it can receive good sunshine, but it doesn't want to have too much sun in the afternoon," said Ms Tsang. "These days with global warming, the heat can get too much for the plant, causing it to dry up."
She has taken on a role akin to a butterfly garden doctor, dispensing her know-how and plants to community gardeners elsewhere in Singapore who are keen to conserve the common rose and common birdwing butterflies.
Khoo Teck Puat Hospital and the neighbouring Yishun Community Hospital are among other gardens that have joined the islandwide movement to conserve the butterflies by planting the dutchman's pipe. The hospitals' 14 gardens and biodiversity are overseen by Mr Simon Chan, the previous chairman of NSS' butterfly and insect group, who patrols the premises twice each day.
Nature is woven into the hospitals' design and ethos. Even the strip of land behind Khoo Teck Puat Hospital's central oxygen tank has been turned into a butterfly paradise, where the dutchman's pipe and other host plants are allowed to grow unfettered.
"We tend to keep it messy because that's what nature wants," said Mr Chan, 62, who diligently documents every wild creature on the hospitals' grounds.
Every butterfly garden matters as they provide a safe, accessible space for butterflies in a dense city-state like Singapore, said NTU Asian School of the Environment research fellow Tharaka S. Priyadarshana.
Dr Priyadarshana said: "These can increase ecological connectivity, allowing butterflies to move between larger green spaces such as nature reserves and parks.
"This network effect is especially valuable in buffering populations against local extinctions and helping species adapt to environmental changes."
Despite the positive results, community gardeners cannot be complacent, as there is always the risk of complications brought about by inbreeding, cautioned both Mr Chan and Ms Tsang.
They cited an occasion where all except two pupae from the fourth generation of common rose butterflies at Khoo Teck Puat Hospital failed to hatch, a grim situation that they attributed to the parents hailing from the same stock.
Mr Chan is currently looking to bring caterpillars from other strongholds into the hospitals' gardens, to maintain genetic diversity.
Architect Khew Sin Khoon, who founded online group ButterflyCircle, said the active planting of the dutchman's pipe is a welcome provision of more food sources for caterpillars of the common birdwing and common rose.
"How long this can be sustained is a different story," he added, noting that butterfly gardens need maintenance, especially since their host plants cannot thrive naturally in the wild.
Mr Khew called on hobbyists to also aid other less glamorous butterfly species that are critically endangered here, some of which rely on host plants that have yet to be identified.
Singapore has 483 butterfly species, of which 74 are considered threatened with the risk of extinction.
He added: "It's laudable that an effort is being made to save butterfly species, but we should extend this attention to more species, not just the iconic ones."