Sunday, 11 March 2018

NSS Kids’ Fun with Frogs at Tampines Eco-Green

By Gloria Seow, Education Committee Vice Chairperson
Photos by Lena Chow & Gloria Seow

The year-end monsoon brings out the croaky choir which was why nightfall of 2 December 2017 saw us gathering at Tampines Eco-Green. Here, the combination of rain and uneven ground creates a multitude of temporary water puddles ideal for egg-laying and tadpole-raising. With torches ablaze, we set off on our frog hunt. The grassy verge between the park and the MRT track quickly produced several Dark-sided Chorus Frogs (Microhyla heymonsi). This 2 to 2.5 cm long frog has a pair of thin blackish lines that run down the sides of its bronze body from snout to rear. Many were amazed that despite its smallness, it has a loud rattling call to attract mates. Another tiny frog of the same size that we flushed was the Painted Chorus Frog (Microhyla butleri) with its distinctive 'hour glass' patterning on its back.

Typically slow moving, we were surprised when two Banded Bullfrogs scaled a tree trunk in a jiffy.

Then we sighted our first Banded Bullfrog (Kaloula pulchra) in the short grass. At 7 to 8 cm long, this frog stands out with its chubby appearance, narrow mouth, and two thick orangey bands that stretch down each side of the body. When threatened, it inflates itself. The Banded Bullfrog feeds on ants, termites, earthworms, flies, crickets, moths and grasshoppers. It advertises its presence with a soothing bellow that can be commonly heard after showers. In our two-hour walk, our first sighting ballooned to some 50 Banded Bull Frogs counted, showing how successful this introduced species is in Singapore.

Dark-sided Chorus Frog

Our island has around 10 commensal frogs with humans (ie. adaptable species able to survive in man-made and disturbed habitats including grassland, roadside puddles and storm drains). All of Tampines Eco-Green’s frogs are commensals. In contrast, the majority of Singapore's native frog species can only live in relatively undisturbed habitats such as primary and/or secondary forests. Hence, such frogs can be wiped out by habitat loss if forests are cleared for development.

Painted Chorus Frog

With so many frogs at Tampines Eco-Green, there were bound to be predators. True enough, Auntie Gloria spotted our first snake – an attractive red-black-and-brown Striped Kukri (Oligodon octolineatus) – a 65-cm long adult that was moving silently on the ground amidst the bushes flanking the grassy path. The half-exposed non-venomous snake froze for a few seconds when we trained our beams on it. It then slithered elegantly into the shrubs and vanished. Next, Auntie Lena found a 7.5-cm long Four-lined Tree Frog (Polypedates leucomystax), easily identified by four thin lines running down its back (although certain individuals have speckled, mottled or plain backs). As an arboreal species, it has expanded flattened tips to its fingers and toes that help it cling onto trees. This frog constructs a foam nest on vegetation or rocks above a pool of water, inside which eggs and tadpoles develop in safety. As they grow larger, the tadpoles fall into the water below or are swept down by rain.

The iridescent Sunbeam Snake was our third snake for the trip.

Only one Asian Toad (Duttaphrynus melanostictus) was seen even though this species is widespread throughout Singapore. It was covered in warts, as is typical of toads, and was sitting upright, quite unafraid of us. Females (11.5-cm) are bigger than males (8.5-cm), as is the case with most other frog species. Another frog that crossed our path was the 5-cm to 6-cm long Field Frog (Fejervarya limnocharis). Being skittish, it made a plop sound as it jumped into a pond to escape from us. If you are using a torch, this frog can be noticed from a distance as it has strong eye shine. Our second snake for the walk was a baby Black-spitting Cobra (Naja sumatrana), unfortunately a dead specimen. We also had sporadic sightings of a rat climbing a tree, fruit bats flying around, a Changeable Lizard (Calotes versicolor), and a Malayan Water Monitor (Varanus salvator). Our final snake was a beautiful Sunbeam Snake (Xenopeltis unicolor) found by Uncle Ivan. The Sunbeam is so named because its smooth scales are iridescent under strong sunlight or camera flash.

Four-lined Tree Frog

On other nights, friends have witnessed a Sunbeam Snake eating a Striped Kukri at Tampines Eco-Green, and seen other cool snakes such as the Reticulated Python (Python reticulatus) and the introduced White-spotted Slug Snake (Pareas margaritophorus). Still, we were mightily pleased that our big group enjoyed this many sightings.

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