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Trip Report - Pesta Ubin 2022: Pulau Ubin Ramble on 11 June 2022

A small rural island off the northeast coast of mainland Singapore, Pulau Ubin is made up of five islets separated by tidal rivers. These islets are now connected by bunds that were built for the purpose of prawn farming to form a single island. The land cover of Pulau Ubin is fragmented, degraded, and highly heterogeneous. It has a variety of habitats, ranging from more natural areas such as mangroves, coastal and secondary forests, and freshwater ponds, to areas with more human influence such as abandoned fruit plantations and quarries. The wide range of habitats that can be found on Pulau Ubin supports a rich diversity of wildlife — some of which can rarely be found on mainland Singapore. These include the Oriental Small-clawed Otter and the Ashy Roundleaf Bat.

Led by Mr.
Pandian Parthasarathy, our group of 21 made our way to Pulau Ubin on a breezy boat ride under good weather. We disembarked at the jetty and stopped at the map of Pulau Ubin where Pandian shared about the history of Pulau Ubin. We then made our way through the village to begin the ramble.

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Pandian explaining the history of Pulau Ubin.

Our first stop was near the native Malayan Banyan just past the Assembly Area. Here, Pandian picked two fruits up off the ground — a bright yellow-orange ripe asam fruit, and a smaller green unripe one. Close by was the fruiting Asam Gelugor tree, which grows up to 27m tall and has a long trunk, smooth grey bark and drooping branches. The leaves are a dark glossy green, long and narrow with a pointed tip and upturned edges. While most people would know that the ripe fruit is used as a common ingredient in Asian dishes such as curries and soups, some might not know that the young leaves of the Asam Gelugor tree are edible, and have a sour, lemony taste.

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Pandian holding the ripe (left) and unripe (right) fruits of the Asam Gelugor, with the tree itself pictured behind him.

The Butterfly Pea was twined along the fence of a residence on the way to Pekan Quarry. It is a climber with short, soft hairs on the stem. Its funnel-shaped flowers are solitary and bloom in a range of colours, including white, pink and blue.

With various food and medicinal uses, the Butterfly Pea is widely cultivated in gardens. The flowers of the Butterfly Pea are edible and used to extract a blue, edible dye that is often used in making kuehs. Being rich in antioxidants, they are also often used in herbal tea. A fun thing to do with Butterfly Pea tea is to add a slice of lemon and watch as the tea changes from a brilliant blue to a vibrant red or deep purple as the pH of the tea changes.

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Butterfly Pea flower (left) and Durians on a Durian Tree.

The main commercial activity on Pulau Ubin was crop cultivation. Various crops including rubber, coffee and durian were cultivated. Pandian directed our attention upwards to see the instantly recognisable sight of durians hanging high above our heads from the branches of a tree. Further down the road, we spotted the thick, fibrous and spiky husk of the durian fruit on the floor. 

As we made our way to Puaka Hill under the shade of the forest, Pandian stopped to point out a termite mound located right next to the road. Termites are remarkably intelligent, building a system of tunnels in the mound which act as an air-conditioning system for the actual nest located beneath the mound. Being soft-bodied insects, this is important for them as high temperatures or direct exposure to UV rays will kill them due to the evaporation of moisture they require to survive. Since termites only build nests where there are rich soils, termite mounds are good sources of clay that can be used in pottery.

Due to climate change, termites are now moving up to trees to build their nests. They typically forage into the hollow insides of the trunk, and travel down the tunnels outside of the trunk to access the ground. This causes the tree to fall, bringing down other trees nearby as well.

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Pandian standing in front of a termite mound.

We then proceeded to make our way up to the highest point of Pulau Ubin — the peak of Puaka Hill. Throughout the journey from Pekan Quarry to the base of Puaka Hill, the melodious singing of the Straw-headed Bulbul could be heard on-and-off. Sadly, we did not manage to see one.

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Base of Puaka Hill.

At the midway point of the climb, we stopped to appreciate nature’s chorus act — the singing of the cicadas. Cicadas are an instrumental species in the ecosystem. They are an important link in the food chain, and provide their host trees a service by identifying and killing off the weak branches of the tree, ensuring that the trees do not waste energy on weak or diseased branches.

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Cicada exoskeleton (left) and Ridley's Hoya flowers.

The next stop on the itinerary was Wei Tuo Fa Gong Temple. On our way there, Pandian pointed out the stunning Ridley’s Hoya flowers that were in bloom at the mangroves near Jalan Jelutong. The pastel pink, ball-like cluster of flowers were a delight to the eye, with the five thick, waxy, triangular petals of individual flowers resembling small stars. Being epiphytes, they naturally grow on tree branches. 

A group member excitedly reported the sighting of a charming male Sultan dragonfly that was perched on a branch right along the path. Males have a dark red body and dark red wings, while females have yellow bodies. Sultan dragonflies can grow up to a length of 56 mm and are known to have the tendency to perch in a vertical position.  

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Male Sultan dragonfly.

A short distance away from the Sultan dragonfly, Pandian gestured for the group to gather. Amongst the leaves of a Sea Hibiscus tree were a number of Cotton Stainer bugs, with their red bodies, black legs, and distinctive yellow cross on black wing cases. They feed only on the seeds of the Sea Hibiscus. Numerous mating pairs were seen.

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A pair of mating Cotton Stainer bugs.

Just as we were about to leave the temple, a Wild Boar made a brief appearance by emerging from the trees beside the temple. Wild Boars are native to Singapore and can weigh up to 100kg with solid body builds. Like many other animals, they can attack when they feel threatened, especially when their young are present. Hence, it is important to keep a safe distance from them and move slowly away to avoid provoking them.

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Wild Boar (left) and Plain Tiger butterfly (right).

Our final stop was the Butterfly Hill, where we first saw the caterpillars of the Plain Tiger on their host plant. Further down, several adult Plain Tigers were perched resting with their wings held upright over their bodies, displaying the underside of their wings. They were of the form alcippoides which has white hindwings. This is the more common form that is observed in Singapore.

Throughout the ramble, Pandian brought up several conservation issues, such as human-wildlife conflict. With limited land and an ever-growing population, human-wildlife conflict has become increasingly common. Pandian raised the example of conflict between Long-tailed Macaques and residents staying near Bukit Timah Hill. Being extremely intelligent, the Long-tailed Macaques have taken to raiding human residences for food. To minimise the amount of human-wildlife conflict that may happen, it is important to educate the public about the local biodiversity and their behaviours, and the possible repercussions of building residences near green areas.

Unlike most rambles that focus purely on nature, the Pesta Ubin: Ramble at Pulau Ubin focused on both human culture and nature. Through clever jokes and insightful sharing, Pandian spoke about how nature and human culture are intertwined. It truly was a fun and unique ramble, and I certainly had many takeaways from the experience. Many thanks to Pandian and the other experienced Nature Society (Singapore) members who shared their wealth of knowledge with me.

Text and photos by: Tan Shin Ying

- Ms. Tan Shin Ying is interning with us for 10 weeks from 17 May to 22 July 2022. Click here to find out more about her.

- Pesta Ubin is made possible by the Friends of Ubin Network to celebrate Pulau Ubin. The celebration was held from 4 - 25 June 2022. More info about Pesta Ubin can be found here.