Frogs In Singapore

ABOUT THE AUTHOR

2006-12-18T11:41:00.000+08:00

The Species of the Order Anura in Singapore

The pride of Singapore’s infrastructure and the status of a leading economical hub in Aisa came at the expense of its biodiversity. Singapore is located in Southeast Asia, where 4 out of 25 biodiversity hotspot lies. Deforestation rates are the highest in this region and Singapore provides the worst case scenario. The rich flora and fauna that once colonized this tropical island declined dramatically after 95% of the forest covers was sacrificed for urbanization and industrialization. Today, Singapore is left with two small fragments of primary forest in Bukit Timah Nature Reserve and in the Central Catchment Area (71ha and 50ha respectively). The use of anurans as an indicator species to study the health of the remaining forest fragments demonstrated the effects fragmentation has brought to biodiversity. A total of 20 species of anurans have been found in the 12 forested fragments I surveyed. This is a far cry from that of our ASEAN neighbors. I conclude the only way to preserve the remaining species of frogs (as well as that of other animals and plants), these remaining forest fragments must be conserved; and we all have a part to play.

Here, I made a record on the species still surviving in the remaining forest fragments in this tropical island. I attempted to describe the morphological differences between the species so as to allow easier identification for the readers and further researchers. In addition, a few behavioral characteristics on each of them were also documented.

Ng Tze How
National University of Singapore
Department of Biological Sciences
Conservation Ecology Lab

Acknowledgement:
Special thanks to

A/Prof Sodhi, Navjot S and Dr. Bickford, David Patrick for their supervision and mentoring

Arvin C.Diesmos; Mary Rose C. Posa; Janice Lee Ser Huai; Qie Lan; Enoka Kudavidanage for their assistance on the field

Pou Limin and Tan Huiming for their lending hand in setting up this blog

and all who have make this possible.

THE SURVEY SITES

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THE RESEARCH PROJECT

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All for the name of SCIENCE!

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2006-12-18T11:38:00.000+08:00

"Every form of life is unique, warranting respect regardless of its worth to man"
- World Chapter for Nature, 1982

THE SPECIES OF THE ORDER ANURA IN SINGAPORE

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THE FAMILY PELOBATIDAE

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Megophrys nasuta
Common name: Malayan Horned Frog or Horned Frog

Megophrys nastua is a classic example of how animals can blend into their surroundings with modified morphological features (sometimes as a form of defense against predation and sometimes as a way of being a better predator). This species is a large frog which can grow to over 100 mm SVL. It has a very wide head relative to its body, but the most distinct morphological feature is it’s leaf-like head and general spiky appearance. From the top of each eye and the tip of the nose, there are prominent pointed projections that give a leaf-like shape. In contrast, its limbs are slender and short and both its fingers and toes are not webbed. It is a general “sit and wait” predator that uses its camouflage well.

It is a slow moving frog that dwells on the ground. As such, it is usually brown in color which further aids in its camouflage to the surrounding dead leaf litter on the forest floor. Locally in Singapore, it has only being spotted in Bukit Timah Nature Reserve and it thus termed rare. Its call is also distinct as it is a very loud horn and it comes only after a few minutes, never more than one or two calls at a time.

Leptobrachium nigrops
Common name: Blacked-eyed Litter Frog

A small to medium sized frog, Leptobrachium nigrops grows up to around 35mm to 50mm in SVL. It has a head slightly wider than its body, with a pair of large distinct black eyes. All four limbs are short and slender with un-webbed fingers and toes. It is usually grey in color with a prominent pattern of black spots and lines on the back.

This frog actually walks instead of jumping and is, at most, only capable of very short jumps. L. nigrops is another inhabitant of the leaf litter on the forest floor. It is not commonly found but can be very abundant in certain locations inside Bukit Timah Nature Reserve, Nee Soon Swamp Forest and MacRitchie Nature Reserve (collectively known as the Central Catchment Reserve).

THE FAMILY BUFONIDAE

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Bufo melanostictus
Common name: Asian Toad

The only “true toad” found locally, B. melanostictus has the typical characteristics of having warty skin and a large, discrete parotoid gland behind each eye and above the distinctive tympanum. It has a small head with medium size limbs. The hind limbs have fully-webbed toes. The back of B. melanostictus is decorated by many round and black-tipped glands which serve the same functions as the parotoid gland, to exude a sticky toxin that can be lethal to small predators (e.g., snakes, dogs, cats). B. melanostictus is medium to large in size and can grow to over 100mm in size.

B. melanostictus is ubiquitous in many places in SE Asia and Singapore is a case-in-point. This species can be found in most urbanized and highly disturbed areas and is only found on the edges of the nature reserves with good forest. The successful story of the toads is attributed by the fact that they only need to go back to the water for reproduction and are thus able to live colonize areas away from the water. They are relatively slow moving and easy to catch, the poison being relatively ineffective on humans (because of our size).

THE FAMILY RANIDAE

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Fejervarya cancrivora
Common name: Mangrove Frog or Crab Eating Frog

Fejervarya cancrivora is a medium sized frog with a SVL of 40 to 60mm. It has a long snout and its tympanum is prominent with tympanumic folds. This frog is grayish brown in color and has dark marking throughout the body. Continuous ridges can be found on the back which runs ventrally. It has strong, well-built hind limbs with toes three-quarterly webbed. The tips of the toes and fingers are pointed.

Just as the name suggested, F. cancrivora can eat crabs which dwell in the mangroves or near the coast where F. cancrivora can be found. This is a human commensal and is often found in disturbed areas all over SE Asia. Singapore is no different, with populations of these frogs being found in many unusual locations

Fejervarya limnocharis

Common name: Field Frog or Grass Frog

Fejervarya limnocharis is a small to medium frog of SVL of 30 to 60mm. It has a long, narrow head. It is morphological very similar to F. cancrivora with prominent tympanum with tympanumic fold, toes and fingers with pointed tips and dark marking over the grayish brown colored body. The main differences are the disrupted ridges found on the back of the body, the toes less than half webbed, and its smaller overall size.

F. limnocharis are common and found on the edges of all nature reserves and nature parks. Due to its size and its powerful hind limbs, it is one of the most difficult frogs to handle.

R. chalconota is a medium size frog which grows up to over 60mm in SVL. It has a long and pointed snout with distinct tympanum which is mostly dark colored. The slender body is accompanied by two hind legs which are relatively long. The tips of the fingers and toes are expanded into round discs which are adhesive. Its toes are fully webbed.

R. chalconota is bright green in the day but turns to brownish green on the back at night. Like what the name suggest, it has lips which are white in color. R. chalconota is uncommon and is found only in relatively good secondary to primary forests but is abundant in such habitat.

Rana erythraea

Common name: Common Greenback or Green Paddy Frog

Rana erythraea is another medium-sized green frog around 40 to 80mm in SVL. It has a long and pointed snout with distinct tympanum. It has strong and long hind limbs with toes half webbed. R. erythraea is green in color and has two bleach colored strips which run dorsa-laterally from each eye, above the tympanum to the end of the body.

R. erythraea are commonly found in and around ponds in urbanized disturbed parks, although it is very difficult to catch. The call can be described as a series of soft squeaky warbles, giggles and ‘pips’.

Rana baramica

Common name: Brown Marsh Frog or Golden-eared Rough-sided Frog

Rana baramica is a small to medium sized frog 30 to 70mm in SVL. The brown and spotted body is slender and the snout is pointed. The tympanum is gold in color. Both the fingers and toes are long with the tips slightly enlarged and toes mildly webbed. R. baramica has small bumps and ridges on the sides of the back that makes it appear rough. The upper lip is white and interrupted with dark bars and patches.

Although it is only found in the nature reserves locally, the distribution is very abundant in these areas. It has a high pitch giggling call that sounds like ‘yip-yip-yip’.

Rana laterimaculata
Common name: Masked Rough-sided Frog

Rana laterimaculata is morphologically very similar to R. baramica except that the tympanum is darker instead of golden. In addition, the upper lip is continuously white in color. The dorsum aspect of R. laterimaculata is also not as distinctly spotted as R. baramica.

Rana laterimaculata is also only found in nature reserves where it can also be quite locally abundant in the right habitats. To complicate things, its call is also a very high pitch giggling and is very much like R. baramica. Even expertd have difficulty in differentiating these frogs from their very similar congeners, R. baramica.

Rana catesbiana

Common name: American Bullfrog

Rana catesbiana is a large, squat frog with large and distinct tympanum. It stocky hind legs have toes which are fully webbed. The tips of the toes and fingers are swollen. The belly of it is distinctly white with the rest of the body is green in color. Dark patches are spotted over the body.

R. catesbiana was imported from America and has been bred locally for food as in the famous “frog leg porridge”.

Limnonectes blythii

Common name: Malayan Giant Frog or Blyth’s Frog

Limnonectes blythii is a one of the largest frog in Southeast Asia with a SVL up to 150mm. It is morphologically very similar to L. malesiana. Its tympanum is distinct with a tympanumic fold (a layer of skin) above it. On the lower lip of the frog, there is also a pair of fang-like structures. The tips of both finger and toes are swollen and the toes are fully webbed except for the fourth toe. In addition, in some adult individuals, there are two humps on the back, located behind each of the eyes.

L. blythii is common and abundant in the nature reserves in Singapore. Due to the size and its stocky legs, it was commonly captured for food. L. blythii could be a cryptic species with at least two distinct forms just in Singapore. While coloration is one obvious difference, some of these individuals have smooth backs compared to others with rough ridges on either side of the back.

Limnonectes malesiana

Common name: Malesian Frog

Limnonectes malesiana is a large, stout frog with a SVL of up to 130mm. It has a broad, large head which is angular in shape, a differentiating characteristic from L. blythi. The tympanum is distinct with a tympanumic fold above it – always lined in black, making a slight black mask for the frog.. The hind legs are stocky with toes more than three-quarterly webbed. The tips of both fingers and toes are swollen. In some individuals of this species, there is a very thin, white stripe between the eyes and run vertebrally down the back. The back is smooth.

L. malesiana is uncommon and found only in the nature reserves of Singapore. It resides in shallow streams and due to its large size, its pair of eyes can be seen very distinctly just above the surface of the water.

Limnonectes plicatella

Common name: Rhinoceros Frog

Limnonectes plicatella is a small frog of SVL of around 30 to 40mm. It has a short snout but its head is broad and large. The tympanum is not very obvious but the tympanumic fold is present. It has relatively short fore-limbs and the toes are half webbed with swollen tips of the toes and fingers. There are continuous ridges that run ventrally along the back. L. plicatella is yellowish brown in color with a bright yellow belly. Perhaps, the most distinct morphological characteristic is the presence of a horn like structure found in many males on the top of the head.

L. plicatella is rare and found only in good forest.

Occidozyga laevis

Common name: Yellow-bellied Puddle Frog

Occidozyga laevis is a small, stocky frog which ranges from around 30 to 50m in SVL. The distance between its eyes is very small and it is decidedly slick. Its stocky, strong legs are accompanied by fully webbed toes where the tips are rounded. Some individuals of this species have a tan colored line down the middle of the back while others have a cauliflower liked tan colored patch on the forehead. The belly of this frog is, of course as suggested by its name, yellow in color.

O. laevis inhabits water puddles with only the eyes protruding from the surface. It is not common and can only be found in nature reserves of Singapore.

THE FAMILY RHACOPHORIDAE

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Nyctixalus pictus
Common name: Spotted Tree Frog

Nyctixalus pictus is unmistakable with its outstanding bright orange coloration accompanied with tiny white spots scattered all over its body. It is a small tree frog with SVL of around 40mm. The relatively big eyes are accompanied by a visible tympanum just behind each eye. The snout is extended and pointed. N. pictus has half-webbed toes with the tips of both fingers and toes expanding into toe pads which are broad and adhesive. These toe pads aid in clinging to leaves, given the arboreal nature to this frog.

N. pictus is a rare species in Singapore and can be spotted only in Bukit Timah Nature Reserve.

Polypedates leucomystax

Common name: Common Tree Frog or Four-lined Tree Frog

Polypedates leucomystax is one of the few real tree frogs found in Singapore. Like other arboreal frogs, the toes and fingers are expanded into toe pads (broad and adhesive) that enable it to climb and hang onto arboreal perches more effectively. The hind limbs are long with half-webbed toes. It has a slim body and a very smooth back. P. leucomystax can be brown or green in color and many have four dark, longitudinal lines while others are spotted with dark or light spots. Coloration, as in many frogs, is highly variable.

P. leucomystax is common and can be found in almost all disturbed human settlements, especially public toilets in or around parks. The call is distinctive, and can be described as a ‘quack’, often in intervals.

THE FAMILY MICROPHYLIDAE

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Kaloula pulchra
Common name: Banded Bullfrog

Kaloula pulchra is a medium-sized frog which ranges from 50mm to 80mm in SVL. It has a small, round head attached to an also well-rounded body. It has short hind legs with toes that are only slightly webbed. The body of this frog is brown, usually with two wide, irregular, tan-colored bands running along the axis of the body.

K. pulchra is both a very attractive frog (hence the “pulchra” species name, meaning beauty) and also very widespread and can be found in disturbed human settlements, ranging from pavement in parking lots to sewage pipes and drains. It has a very remarkable defensive mechanism where it will bloat up into almost a perfect sphere, preventing predators from swallowing it. In addition, it also secretes a very sticky white latex that is probably mechanically defensive against its predators. Once handled, the substance is hard to wash off the hands.

Microphyla heymonsi
Common name: Dark-sided Chorus Frog

Microhyla heymonsi is a tiny frog with a maximum SVL of no more than 30mm. Like almost all frogs in the genus Microhyla, it has long hind legs with toes which are not webbed. Perhaps the most distinctive characteristic of this frog is its general coloration: lighter brown on the back of the animal with dark colored bands running on both sides from the snout to the groin on either side of the body. The frog is smooth and can sometimes have a mid-dorsal stripe running down the center of the back. The size and coloration pattern make it very difficult to spot in the dried leaf litter which it mostly inhabits.

However, despite how hard it is to find these frogs, they are very common and live in most urbanized parks and on the edges of the nature reserves. Though difficult to spot, its calls is characteristic of its presences as the series of the creaking sounds made by the males in low-lying and wet areas forms a chorus which is unmistakably recognizable.

Microhyla butleri
Common name: Painted Chorus Frog

Microhyla bulteri is another tiny frog with a SVL of 20mm to 30mm. Characteristic of all Microhyla, it has long hind legs. Its toes are not webbed and the tympanum is not visible. Perhaps, the most distinctly characteristic of this frog is its dark brown body and decorated by tan-colored patterns that run across the back which further enable it to camouflage well in the leaf litter. In general, this frog is not smooth, but instead has a rather granular or slightly bumpy dorsum, another distinguishing feature that separates it from its congeners.

M. bulteri is found in disturbed forest and is uncommon but widespread in Singapore.

Kalophrynus pleurostigma

Common name: Black-spotted Sticky Frog or Red-sided Sticky Frog

Kalophrynus pleurostigma is a relatively small to medium-sized frog which grows up to a maximum of 60mm in SVL. It has a very pointed snout, a narrow head and distinct tympanum. The toes and fingers are short and the toes have very little or no webbing. One distinctive characteristic of this frog is the presence of a black spot on the inguinal area of the groin region, just in front of each hind leg. The back of this frog looks a bit rough with many tiny raised spinules.

K. pleurostigma is usually brown in color with either side a bit orangey. When handled, it secretes a sticky substance which is either toxic or has mechanical glue-like properties and serves as a defense mechanism.

Views From The Helpers

2006-12-07T00:35:00.000+08:00

What did some of the student helpers have to say?

"I think frogging is a fun and enriching experience as it allows me to see out of the textbookin a whole new dimension" - Dong Xiang, year 1 Statistic major

"Interesting and it border the mind, and intro to me the night life of amphibians" - Shijun, year 3 maths major

"Frooging has been an interesting experience. Conserving the environment is very important. If not, we might not have interesting frogs to see" - Huiting, year 1 Life sciences major

"Helping up in frogging was a treat for me. It is exciting and eye opening as i never imagined there is such a rich diversity of flora and fauna in Singapore. It is really great exposure for anyone interested in biology" - Huiling, year 1 Life sciences major

FIELD PHOTOS

2006-12-07T00:29:00.005+08:00

THE DREAM TEAM
Presenting to you
Dr. David Bickford

Reuben

Jennifer

A Day in the Field

Fresh out from the lab

Into the NUS cab... Ready to Go

It is Always food before Work.

We Conquer the highest Mountain In Singapore

Operation Orders: Who goes Where. No frogs Shall Escape

You go first...

Then Me...

Toe Clips,,, For DNA

Load the Cab.. We are going Home!