Ansonia sp; Fig. 1a

Snout obliquely protruding in lateral view; snout tip pointed in lateral view; body generally slender; dorsum brown to olive, with blurred dark markings; finely warted dorsally, warts without keratinized spines; dorsolateral warts slightly larger, some fused to form a ridge from above tympanum to shoulder; belly gray with dense brown spots; throat dark brown; light marking under the eye and between angle of jaw and shoulder; toes and fingers possess rounded, slightly swollen tips; iris black with dense golden iridophores; more reddish in anterior and posterior sector; tympanum distinct, small.—This species was common at Fawzy Fall near Nepenthes Camp. Specimens were observed at or in the stream, sitting on low vegetation or rocks.

Genetic barcoding and sequence analysis (see Appendix 1: Specimen vouchers section for accession numbers) suggest that this population is conspecific to the unnamed clade Ansonia sp. 3 in Matsui et al (2010) from the Kelabit Highlands in northern Sarawak.

Ansonia leptopus (Günther 1872): Brown Slender Toad; Fig. 1b

A slender toad, variable brownish in color, sometimes with tinges of orange; only faint color markings, indistinct crossbars on thigh and shank; small rounded warts on dorsum, larger flat warts at lateral dorsum and flanks; throat dark with lighter mottling; abdominal skin pebbled, mostly amber in color; snout projecting obliquely in lateral view; finger and toe tips rounded and slightly swollen; toes three-fourth webbed in males slightly less in female; no tarsal ridge; tympanum visible, small; iris golden with black network.—One female was recorded from a rocky tributary of Sungai Maliau. This species occurred in syntopy with Leptolalax fritinniens.

Ansonia longidigita Inger, 1960: Long-fingered Slender Toad; Fig. 1c

Snout obliquely protruding in lateral view; obtuse, rounded snout tip in lateral view; small conical warts on dorsum and dorsal side of limbs, often with small black spines giving a rough appearance; limbs and fingers long; almost uniformly brown to dark brown above, sometimes with reddish hue; diffuse scattered dark spots on the body; crossbars on thigh and shank may be indistinct in a dark marbled pattern; cream to amber with dark markings ventrally; darker on the throat and chest; toes and fingers bear rounded, slightly swollen tips; iris mostly golden to reddish-golden, with black reticulated pattern and thin reddish ring around pupil; tympanum distinct but small.—Two specimens were collected at the streams of Ginseng Camp, perching on low vegetation.

Ansonia spinulifer (Mocquard, 1890): Spiny Slender Toad; Fig. 1d

Snout obliquely protruding in lateral view; snout tip obtuse and rounded in lateral view; body generally slender; dorsum mostly black, with lighter yellowish or reddish warts laterally and in bands of such lighter warts on fore- and hind limbs; with a light cream, gray or reddish patch between shoulders; coarsely warted dorsally, warts with keratinized black spines; belly pebbled in texture, dark brown to black in color, with white markings; ventral side of thigh pebbled with scattered white spots; toes and fingers possess rounded, slightly swollen tips; iris black with some reddish stippling and a reddish ring around the horizontal pupil; tympanum distinct, vertically oval.—This species was common along the river at Ginseng Camp. Specimens were observed sitting on low vegetation close to the river. Encounters included numerous juvenile specimens along the Ginseng Camp stream below Ginseng Falls. One tadpole was captured at the river above Ginseng Fall.

Ingerophrynus divergens (Peters, 1871): Forest Toad; Fig. 1e

Body stocky; two hard ridges between eyes; parotoid gland narrow, longer than wide, posteriorly followed by row of warts; in general, coarsely warted above; warts pointed, with keratinized spinules; ventral skin coarsely pebbled in texture, cream with black spots in color; brown above with darker markings between eyes and on back; narrow vertebral stripe; limbs with cross bars ; sometimes with orange or reddish warts; ear drum visible but not different in color from surrounding skin; iris golden or reddish-gold with a black network.—Ingerophrynus divergens was common in the forest along Sungai Maliau and its tributaries and Agathis Camp. After rainfall, calling choruses of 10–20 males were encountered at some shallow, slow moving tributaries of Sungai Maliau.

Leptophryne borbonica (Tschudi, 1838): Cross Toad; Fig. 1f

A slender toad with long limbs, long fingers and toes; generally mid to dark brown above with various dark markings, particularly a diagnostic thick dark ‘X’-shaped mark, with cream contour line, on middle of dorsum and a less pronounced one on shoulder to head transition (in our specimen separated into distinct spots); lips with dark bars; belly cream with some dark markings; underside of thigh orange; parotoid glands narrow, elongated and indistinct, extending posteriorly into dorsolateral ridge of warts; iris golden (sometimes reddish in anterior and posterior sector of iris) with black reticulate pattern; ear drum indistinct in color and posteriorly covered by skin; slightly swollen finger and toe tips;—A juvenile was collected at Ginseng Camp, along the rocky stream above Ginseng Falls, perching on low vegetation.

Phrynoidis juxtasper (Inger, 1964): Giant River Toad; Fig. 1g

A large and stocky toad; with large, prominent parotoid gland behind eye; large warts all over the dorsal side; warts rounded to conical, bearing spinule; dorsal coloration uniformly grayish to mud brown; dark markings present or absent; ear drum small and indistinct; iris, golden with fine, dark reticulation—Phrynoidis juxtasper is common along Sungai Maliau, however, calling activities sightings of adults were low during the survey. Apart from Sungai Maliau, the species was also present at Nepenthes and Agathis Camp.

To our knowledge, photos of P. juxtasper tadpoles have only been published for Sumatra (Manthey and Grossmann 1997:32). Larvae from Sungai Maliau (Fig. 1h–j) were collected in quiet, shallow (< 20 cm) shore waters among rocks. One tadpole (ZMH A12647) was barcoded (accession: MG909569) to exclude erroneous assignment to P. asper. The tadpole body is ovoid in dorsal view, widest behind eyes, and slightly depressed dorsoventrally. The snout is short and a steeply inclined slope in lateral view. The eyes are dorsolateral in position. The tail is short, comprising only approx. 55% of total length. The coloration is generally dark brown above with plenty of yellow dots. The tail is less dark than the body; it bears 2–3 bright yellow spots along the upper edge of the tail’s muscular part. The tail fin is weakly pigmented and moderately high; the tail tip is broadly rounded, blunt. Two keratodont rows are present on the upper lip, three on the lower lip. Lips are broadly expanded to form a sucker mouth. The ventral side is mostly transparent. The gut is arranged in a conspicuously transversely oriented coil. Metamorphs and juveniles were encountered in large numbers along Sungai Maliau and slightly larger juveniles along the Maliau tributaries, respectively. The presence of larvae, juveniles, and slightly larger juveniles at distance from Sungai Maliau suggested that a major breeding event had occurred most likely in December/January and juveniles were migrating into the forest.

Fejervarya limnocharis (Gravenhorst, 1829): Grass Frog; Fig. 2a

Body slender to stocky; narrowing snout in dorsal view; snout projecting well beyond lower jaw in lateral view; finger and toe tips not expanded; prominent broken longitudinal ridges on back; coloration from shades of gray to brown and greenish hues, with scattered dark blotches; often with vertebral stripe; alternating light and dark marks across lips; belly white or cream underside of hind limb flesh colored; males with dark throat markings; ear drum moderately distinct; iris brass in the upper sector, silvery in the lower; outside the iris the eye bulb is white-bluish.—Fejervarya limnocharis is not a true forest species, although it may occur at clearings. It is present in rural areas such as rice paddies, road ditches, or ponds and puddles logged areas. It is common at puddles and swampy areas of the Study Center and ditches along the road to Belian Camp.

Limnonectes ingeri (Kiew, 1978); Fig. 2b

A large, heavy frog with muscular, long legs; area between nostril and eye smooth, not forming an edge (i.e., no canthus rostralis); head broad and flat; finger and toe tips slightly bulbous but not expanded; toes fully webbed; dorsal skin finely textured, shagreened, with scattered tubercles and small ridges; multiple conical tubercles on top of the eye; supratympanic fold long, with black line, bending in angled manner around tympanum to shoulder; tympanum moderately distinct (colored as surrounding skin); color homogeneously brown above; some black blotches posterior to shoulder; sometimes red on thigh; dark markings on upper and lower lip; a thin midline cream colored streak can be present or absent; thin banding on thigh; venter white, dotted brown, throat dark mottled; thighs pale with some cream spots; iris densely stippled silver-gold on black background, venation pattern.—This large species was encountered in the riparian habitat along Sungai Maliau, from one of its tributaries.

Limnonectes sp. Creek Frog complex; Fig. 2c

Although the Creek Frog species complex (formerly known as L. kuhlii) consists of a multitude of species (McLeod 2010, Matsui et al. 2016), a general short description can be given: SVL to 88 mm in males; robust frogs with very muscular thighs; fully or partially webbed toes; eyes more upward directed than in other species; skin with conspicuous reticulate, polygonal pattern of small ridges above; rough tubercles may be present on upper side of shank and thigh; color above with ochre to mid-brown background and extensive dark brown to olive-brown blotches; broad bands on arms and legs; belly white to cream with mottling laterally and on chest and throat; finger and toe tips slightly swollen; distal phalanx of toes sharp and can penetrate the skin for defense against predators; ear drum invisible; iris silver-gold to brown, with four dark radials; odontoid processes on anterior of lower jaw.—The taxonomy of the frogs formerly known as L. kuhlii is in a state of taxonomic transition because it has been demonstrated that L. kuhlii, in fact, is a species complex of similar frogs consisting of many species in Sabah and Sarawak (McLeod 2010, Matsui et al. 2016) covering a wide range of body sizes (Kueh et al. 2010b). New species names have not been proposed yet for many of the genetically well-delimited lineages and, thus, we list the barcoded frogs from our survey in The Appendix 1: Specimen vouchers section under the respective clade number from Matsui et al. (2016) that they matched best genetically. Specimens from this species complex where recorded at Sungai Maliau tributaries, Agathis Camp and Ginseng Camp streams. According to a preliminary comparisons using sequence data of Matsui et al. (2016) our samples represent Matsui et al. (2016) Lineages 2, 5, 12, and 17.

Limnonectes leporinus (Andersson, 1923): Giant River Frog; Fig. 2d

Robust large frog with strong hind limbs and broad triangular head; snout long and tapering in dorsal view, projecting well beyond lower jaw in lateral view; mostly smooth, dorsal skin texture shagreened, occasionally with scattered elongated tubercles and short ridges on back, esp. in juveniles; tubercles on top of eye; toes fully webbed; grayish, sandy brown to mid-brown above with scattered dark spots; dark band between eyes; dark streak from eye to snout along an edge between eye and nostril (canthus rostralis); dark markings on lips; dark below supratympanic fold and upper part of ear drum; supratympanic fold being in a moderate angular manner around tympanum; tympanum moderately distinct; hind limb barred above; belly uniform cream; throat faintly mottled; odontoid processes on anterior of lower jaw; iris golden with three more or less pronounced dark radial areas (anterior, posterior and ventral sectors) and fine black venation.—This large river frog is common along lowland rivers of Sabah and Sarawak and was detected at the Sungai Maliau tributaries, Ginseng and Agathis Camps. Often these frogs sit on the ground of the river bank a few meters from the water line. One male was observed building a nesting site, i.e., a circular depression in the fine gravel of one of Sungai Maliau’s tributaries. The male was calling with a deep single note and a female was noticed nearby.

Limnonectes paramacrodon (Inger, 1966): Lesser Swamp Frog; Fig. 2e

Snout long and tapering in dorsal view; bulging bluntly beyond lower jaw in lateral view; toe tips slightly widened, finger tips rounded and not widened; toes webbed to almost the tip, except for Toe IV; webbing; dorsal side sandy brown, mid-brown or reddish brown, uniform or with irregular markings; supratympanic fold bending around tympanum; tympanum almost entirely covered with dark fleck below supratympanic fold; dark streak from eye to nostril along canthus rostralis; contrasty light and dark markings on upper and lower lips; faint banding on thigh; venter yellowish; throat mottled; dorsal skin texture shagreened with some low tubercles and short ridges on back; odontoid processes on anterior of lower jaw; iris golden with four conspicuous dark radials and fine black venation;—L. paramacrodon was common in the riparian habitat of Sungai Maliau. Numerous juveniles were encountered at swampy areas in the forest along Belian and Wildlife trails near the Study Center, suggesting that this species might use these swampy areas for reproduction.

Leptobrachium abbotti (Cochran, 1926): Lowland Leaf-litter Frog; Fig. 2f

Limbs slender; head wider than body; eyes large; toes nearly free of webbing; hind limbs relatively short; forelimbs long and thin; supratympanic fold arched around ear drum; upper part of tympanum with a dark mask; skin of dorsum smooth to granulated; dark brown above, with a darker pattern on forehead; ventral side smooth; abdominal skin dark grayish with white spots partially arranged in rows; throat white with grayish markings; iris dark brown to black; beyond the iris the eye is blueish.—The species was present on the forest floor along Sungai Maliau (Wildlife Trail) and at Nepenthes Camp. A calling chorus of this species was noticed at Agathis Camp.

Leptolalax fritinniens Dehling & Matsui, 2013: Twittering Slender Litter Frog; Fig. 2g

Snout rounded; vocal sacs of males subgular and bipartite; supratympanic fold angled; tympanum distinct, dark; venter white with darker blotches; generally grayish or brownish to anthrazite above with some light brown flecks and large dark blotches; blotches and flecks not bordered in light color; dorsal surface of upper arm and part of hind limb lightened; thigh with distinct banding; iris grayish with reddish sector dorsally and red iris edge around pupil.—Calling males were detected along a tributary right of Sungai Maliau. This side stream was rocky and had large boulders. Males perched on low vegetation (< 50 cm) up to 10 m away from the waterline, elevated on the steep river banks.

Megophrys nasuta (Schlegel, 1858): Bornean Horned Frog; Fig. 2h

Body robust, particularly in females; relatively short hind limbs; head large, wider than long; prominent triangular, dermal appendages on tip of snout and upper eyelids; ear drum hidden; two pairs of parallel dermal folds on back; dorsal skin mostly smooth with scattered tubercles, some of the conical; tips of fingers and toes rounded, not expanded; toes webbed at base; dorsum brown with darker markings; a dark bar from eye to upper lip; limbs with narrow crossbars; throat reddish-brown to dark brown in males; posterior half of ventral side whitish with dark flecks; iris dark brown to reddish brown, somewhat lighter in upper part.—The species was not active at the time of our survey. One specimen was encountered near Study Center, Belian Trail.

Chaperina fusca, Mocquard, 1892: Saffron-bellied frog, Fig. 3a

SVL up to 24 mm, males smaller; moderately slender body with long hind-limbs; head narrower than body, with rounded short snout; finger and toe tips slightly widened, without webbing; a tiny whitish skin spur is located at each elbow and heel; dorsal skin structure smoothly pebbled, venter smooth, small tubercles on upper side of hind limb; dorsum mottled grayish on dark brown background; upper side of limbs brown with dark brown bands or markings; white dots laterally and on limbs; ventral side with large, bright yellow spots; tympanum visible but indistinct; pupil elliptical and horizontal; iris black with golden stippling.—The species was observed and photographed at Nepenthes Camp but likely is not restricted to the MBCA southern plateau. No specimen was collected.

Microhyla berdmorei (Blyth, 1856): Berdmore’s Narrow-mouthed Frog, Fig. 3b

Broad flat body with long hind limbs; snout contour in dorsal view tapering but narrowly rounded; finger tips moderately widened, toe tips clearly widened into discs, somewhat truncated digital discs; fully webbed toes, except for fourth toe; dorsal skin texture relatively smooth, with scattered fine tubercles; color brown above, with dark and light-edged polygonal marking from shoulder to mid-back; banding pattern on limbs; venter yellow, ventral side of limbs dull yellow; throat dark and finely mottled brown; iris brass with dark reticulate pattern; ear drum invisible;—This microhylid ground-dwelling species was encountered at and around swampy areas and roadside ditches along Belian Trail.

Microhyla petrigena (Inger & Frogner, 1979): Pothole Narrow-mouthed Frog, Fig. 3c

SVL up to 18 mm; short, stocky body; long hind limbs relative to body; narrow, small head; snout short; skin mostly smooth with fine tuberculation; only three fingers present; finger and toe tips expanded, blunt; toes fully webbed except for fourth toe; general color in shades of brown above (including ochre, chocolate and reddish tones); finely mottled, larger dark markings at flanks, at anus and at thighs are outlined with light edges; dark marking central on back, constricted just behind shoulder level and expanding posteriorly; light stripe from eye to shoulder joint; ventral side mostly chocolate with conspicuous white blotches; ear drum invisible under skin; iris finely stippled silver to brass on black background, with orange ring around pupil.—This small species was recorded from a stagnant forest pool near Nepenthes Camp. It is tentatively assigned to M. petrigena based on the reduced first finger and white marking on the belly (also following mentioning in Matsui et al. (2014) from the same locality). The specimens were found near a stagnant forest pool, although M. petrigena typically has been reported breeding in potholes of rocky streams (Inger et al. 2017).

Kalophrynus cf. barioensis Matsui & Nishikawa, 2011: Bario Sticky Frog, Fig. 3d

Stocky, broad, flat body, short limbs; narrow head relative to body, short pointed snout; all fingers short except third; outer finger and toe very short, nub-like; webbing reduced; dorsal skin texture granulated to moderately tuberculate; color red-brown above, with faint dark markings; toes and fingers bright orange to red; inguinal spot light colored and distinctly edged dark; row of well-defined cream tubercles from above ear drum towards groin; dark-edged cream inguinal spot; similar smaller spots on rear of thigh; iris bronze with fine reticulate pattern; pupil horizontal; ear drum indistinct.—The species was tentatively assigned to K. barioensis based on 98% similarity with sequence KM509147.1 from GenBank, despite deviation from the original description of K. barioensis in inguinal spot color, thigh pattern, and dorsal color. The species was found to be abundant in the heath forests (Kerangas) of the Maliau Southern Plateau. Males call during the day from the forest leaf litter away from water (in accord with the original description of K. barioensis; Matsui and Nishikawa 2011). Preliminary evidence suggests that this species is a phytotelm breeder using Nepenthes pitchers to deposit eggs (Ahmad and Wong 1998).

Kalophrynus meizon Zug, 2015: Borneo Big Sticky Frog, Fig. 3e

Body stocky, head small in relation to body, snout pointed but short; limbs moderately long; finger and toe tips not expanded, third finger conspicuously long; toe webbing variable, approx. half of toes; dorsal skin structure finely pebbled in females, finely spinose in males; dorsal skin color sand to brown often with darker markings and black spots; a narrow light line from snout tip to groin separates the dorsum from the darker or orange flanks; dark spot in groin region; abdomen light gray, throat orange to rusty; pupil horizontal, iris gold-brown.—The species was recorded by photograph for Nepenthes Camp; no specimen was collected.

Kaloula baleata (Müller, 1836): Brown Bullfrog, Fig. 3f

Body squat and clumsy; hind limbs relatively short; head significantly narrower than body, snout short, eyes relatively small; tympanum invisible; fingers and toes long, distally expanded, toes more so; toe webbed at base; dorsal skin granular with scattered tubercles; even lower jaw with rough skin; dorsal skin coloration quite variable, usually marbled in shades of brown and gray, often darker in central part of dorsum; pupil elliptical, horizontal in orientation; iris dark amber.—The species is mostly seen during breeding activities when the loud deep calls of the males can be heard. The specimen in Fig. 5b was photographed near Study Center; no specimens were collected.

Metaphrynella sundana (Peters, 1867): Tree Hole Narrow-mouthed Frog

Short, narrow, somewhat obtuse snout; toes and fingers relatively large, fleshy, and bear expanded digital discs; toes webbed half; dorsal skin texture warty; color mostly brown and gray, variable pattern but commonly with a large dark constricted marking on the dorsum; fingers and toes often with yellowish or orange; iris black with some bronze stippling; pupil horizontal; ear drum rather indistinct.—M. sundana was present in the forests of the Southern Plateau. Reproductively active males called from tree-holes, some of them several meters above ground. Account by acoustic identification, no photo vouchers, none collected.

Amnirana nicobariensis (Stoliczka, 1870): Cricket Frog; Fig. 4a

Slender body; head long and narrow; long hind limbs with great jumping performance; fingers and toes elongate and with slightly swollen tips; toes half webbed; long snout, pointed in dorsal view; snout projecting lower jaw, narrowly rounded in lateral view; dorsal skin texture finely pebbled or granulated; dorsal side uniform mid-brown to marbled brown; dorsal side of hind limbs with darker bars; black streak at side of head starts from snout, broadens to band under canthus rostralis and continues behind eye covering the ear drum and beyond; dorsolateral fold present, thin but continuous from eye to pelvic region; tympanum large and distinct; upper lip als uniform white streak that continues onto rictal ridge behind jaw joint; venter cream, throat cream with darker mottling; thighs in pale flesh color below and weak banding above; iris dark reddish-brown below, golden above.—This species commonly follows human alteration of landscapes such as rural areas, road ditches and clearings; it does not enter the forest. At Maliau Basin it is present in large numbers at the pond of the Study Center and in ditches along the roads.

Abavorana luctuosa (Peters, 1871): Mahogany Frog; Fig. 4b

Moderately stocky with moderately long limbs; toes webbed to less than half of their length; finger and toe tips slightly expanded, narrowed to the tip; snout protruding beyond lower jaw and rounded in lateral view; area between eye and nostril smooth; skin texture smooth; a mahogany-brown area is delimited by a circumferential thin white to orange line on the dorsum and head; cream streak on upper lip from under the eye to shoulder; remaining parts of body mostly black; arms and legs variable, with black banding on brown background or black with banding in light gray; flanks gray with or without black dots; tympanum large and distinct; under side dark gray with white spots on venter and vermiculated pattern on thighs, zebra pattern on underside of shank; webbing; ear drum black, distinct, and large; iris dark brown to black, except for golden upper fifth;—The species was present with adults and larvae in a pond near Nepenthes Camp. For size and altitudinal range see Kueh et al (2010a).

Chalcorana megalonesa Inger, Stuart & Iskandar, 2009: Large White-lipped Frog; Fig. 4c

A relatively large species in the genus; body slender; limbs, fingers, and toes long; head long and narrow; snout pointed; snout projects with sharp tip beyond lower jaw in lateral view; snout longer than eye diameter; canthus rostralis present; fingers and toes long, bearing significantly expanded tips in form of adhesive disks with circummarginal grooves; tympanum very distinct and large (in males); dorsal skin texture finely granular; brown above with scattered dark spots; flanks often green otherwise brown; upper lip all cream in color, cream streak extends beyond jaw joint to shoulder; ventral side cream on venter and throat; under side of thighs flesh colored; iris golden with fine black venation and more reddish hues in anterior and posterior sectors.—Chalcorana megalonesa is a common sighting at the Study Center, Sungai Maliau tributaries, Agathis river and streams, and Ginseng Camp streams. Early stage tadpoles were present (not collected) in an isolated side puddle of one of the Sungai Maliau side streams.

Huia cavitympanum (Boulenger, 1893): Hole-in-the-head Frog; Fig. 4d

Body moderately stocky but with strong and long hind limbs; toes and fingers with terminal expanded and slightly pointed discs; toes fully webbed; dorsal skin texture mostly smooth, flanks with low tuberculation; color dark brown on dorsum, separated from lighter flank by ochre to orange dorsolateral stripe; dorsolateral fold broken; dark blotches expand from eye posteriorly, ventrally and anteriorly; hind limbs distinctly banded; ochre to orange line along upper side of shank; ventral side uniform yellow; tympanum distinct but small, sunken in, transparent; iris bicolored, dark reddish-brown below and beige to golden in the upper third.—The species has large tadpoles that are highly adapted to fast currents. The tadpoles can hold on to rocks in very fast currents by applying their conspicuous abdominal sucker. Because of this larval adaptation, this species is linked to clear cascading streams, however, individuals can occasionally be found at some distance from the stream. We recorded the species from the Fawzy Waterfall area.

Hylarana erythraea (Schlegel, 1837): Green Paddy Frog; Fig. 4e

Body moderately robust with long and muscular hind limbs; head and snout relatively long and moderately narrow; finger and toe tips only moderately expanded to rounded discs; toes webbed to half; dorsal skin texture smooth to granular, areolate at the flanks; color predominantly green above; dorsolateral fold thick, continuous and cream in color, bordered in dark brown; upper lip cream without marking; upper lip streak continues posteriorly in a lower longitudinal stripe at lower flank; upper side of limbs sandy brown; throat, chest and abdomen ventrally all white; thighs flesh to orange in color tympanum conspicuous, large, dark in color; iris golden in upper part, darker below, with dark mid-horizontal band.—At Maliau, the species is abundant at the Study Center Laguna and roadside ditches. H. erythraea and A. nicobariensis frequently occur together in many Bornean rural water bodies, such as village ponds and paddy fields.

Meristogenys orphnocnemis (Matsui, 1986): Northern Torrent Frog, Fig. 4f

Slender (males) to moderately stocky (females) body with long slender legs; snout moderately long; tips of toes and fingers expanded, slightly rhomboidal; toes fully webbed; skin texture finely shagreened; dorsolateral fold present; color above brown, with scattered dark dots and light markings; upper lip without dark markings; upper side of thigh broadly banded; throat, chest and belly white or cream; males with lateral dark vocal sack areas on throat; rear of thigh mottled dark with light spots; iris golden in upper and lower sectors, reddish in anterior and posterior sectors. —Meristogenys orphnocnemis was most common at Ginseng Camp streams, but also recorded at one of the larger, rocky Sungai Maliau tributaries. Most often individuals of this species perched on roots, rocks or the soil at the slopes of the stream banks. The species identity was confirmed by genetic barcoding and matching to previously published data (Matsui et al. 2006, Shimada et al. 2011a,b). Tadpoles were found at night while adhering to rock surfaces at a stream next to Ginseng Camp. Tadpole identification followed the key in Shimada et al. (2015).

Odorrana hosii (Boulenger, 1891): Poisonous Rock Frog; Fig. 4g

Body moderately robust with long and muscular hind limbs; toes and fingers long; tips of fingers and toes expanded to large rhomboidal discs; toes fully webbed; webbing dark in color; dorsal skin texture shagreened to granulated; ventral skin texture smooth anteriorly but areolate on posterior belly and thigh; color mostly green above, flanks can be brown; dorsolateral fold present but weakly developed, set off by dark line; upper side of limbs green or brown, with banding; dark stripe from nostril to eye along canthus rostralis; upper lip cream without markings, cream stripe continues to shoulder; ventral side white; tympanum distinct, dark in color, moderate in size; iris silver to gold in upper and lower part with abundant black reticulating pattern, mostly black in anterior and posterior part, with narrow golden ring around pupil,—Odorrana hosii was found at the rocky stream below Ginseng Falls perching high up the steep banks.

Pulchrana picturata (Boulenger, 1920): Spotted Stream Frog; Fig. 4h

Body slender to moderately robust; limbs moderately long; head relatively narrow, moderately long snout; tips of digits slightly swollen; webbing to approximately half the toes; granular dorsal skin texture; color black with yellow to red spots and angular blotches; colored line from snout to eye and along upper eye lid; no continuous stripe from eye to groin; banded pattern on upper side of limbs; venter dark gray with scattered cream spots; tympanum distinct, black; iris coppery, with reddish narrow ring around pupil and abundant black reticulate pattern.—This species prefers rocky streams. It occurs at the Sungai Maliau tributaries, Agathis Camp and Ginseng Camp; however, the species was not abundant during our survey. Pulchrana picturata and P. signata belong to a species complex that has not been fully resolved yet on the island of Borneo.

Pulchrana signata (Günther, 1872): Striped Stream Frog; Fig. 4i

Body slender to moderately robust; limbs moderately long; head relatively narrow, moderately long snout; tips of digits slightly swollen; webbing to approximately half the toes; granular dorsal skin texture; color black with yellow to red angular spots or blotches; colored line from snout to eye, along upper eye lid and posterior to groin; banded pattern on upper side of limbs; venter gray, thigh darker; tympanum distinct, blackish; iris coppery, with reddish narrow ring around pupil and abundant black reticulate pattern.—Pulchrana picturata and P. signata belong to a species complex that has not been fully resolved yet on the island of Borneo. The specimen reported here was found at a forest pond near Nepenthes Camp.

Staurois guttatus (Günther, 1858): Black-spotted Rock Frog, Fig. 4j

Body slender; snout long, pointed and protruding in lateral view; long fingers and toes, tips of digits broadly expanded; webbing of toes shiny turquoise blue; upper head and back yellowish brown to olive brown with dark spots on back, light green or yellowish green at the flanks with white dots; limbs brown to green above with more or less pronounced dark banding; lips without bars; outer third of digital discs with light cross band; dorsal skin texture pebbled or slightly warty, especially dorsolaterally; ear drum distinct but small; ventral side of throat, breast and belly white, more yellowish anteriorly; underside of limbs not white but greenish gray; iris gold to copper in upper sector, black in anterior and posterior sector and pale silvery in lower sector, narrow color ring around pupil (copper except for lower pale silver sector).—Staurois guttatus is a common species along medium sized streams of Maliau. It was quite abundant at the Sungai Maliau side streams, Agathis Camp and Ginseng Camp. Individuals typically perched on low vegetation (< 150 cm) along the bank of streams or on vegetation growing among boulders in the stream.

Staurois tuberilinguis (Boulenger, 1918): Green-spotted Rock Frog, Fig. 4k

Body slender; snout long, narrow, edged, pointed and protruding in lateral view; long fingers and toes, tips of digits broadly expanded; webbing of toes shiny turquoise blue; upper head and back yellowish brown to olive brown with dark spots on back forming marbling, flanks not sharply different from back; limbs brown to olive brown above with distinct dark banding; lips without bars; outer third of digital discs with light cross band; dorsal skin texture pebbled, tuberculate on flank; scattered short longitudinal ridges on dorsum and flank; ear drum distinct but small; ventral side of throat, breast and anterior belly white with diffuse dark spots; underside of limbs not white but brown to gray; iris golden in upper sector, black in anterior and posterior sector and pale golden in lower sector, narrow gold ring around pupil.—The species was abundant at Fawzy Waterfall. The species was distinguished from S. parvus by overall size (Matsui et al. 2007)

Feihyla kajau (Dring, 1983): White-eared Tree Frog, Fig. 5a

Slender body; snout very short and blunt, eyes slightly forward directed; finger and toe tips broadly rounded; webbing at base of outer fingers; toes half-webbed; dorsal skin texture finely shagreened; wavy edge along outer border of fourth finger and forearm and outer foot; color green above abruptly ending at flanks, brown posteriorly (pelvic region), scattered white dots above; venter white anteriorly and transparent posteriorly; iris silvery below and golden above, with some dark reticulation and golden ring around pupil; pupil horizontally oval; ear drum present but small and inconspicuous due to coloration of skin.—A number of individuals of F. kajau were found at a small forest stream with pools of low flow velocity. The stream is crossed by the trail from Fawzy Waterfall to Nepenthes Camp.

Chiromantis inexpectatus Matsui, Shimada & Sudin, 2014: Bornean Opposite-fingered Tree Frog, Fig. 5b

Body slender with relatively long fore limbs; head wide and flat; snout short; eyes slightly forward directed; outer fingers webbed at base; toe and finger tips expanded to adhesive discs; dorsal skin texture smooth, venter smooth; color yellow to brown above with dark spots; venter semi-transparent pink or red, with two longitudinal white streaks; brown band runs from tip of snout to flank at half of body, adjoined below by a cream stripe; iris amber, fading into beige at the dorsal and ventral periphery; eye moderately large; pupil without distinctly colored edge; pupil oval horizontally; ear drum present, small, inconspicuous.—This small rhacophorid species was described by Matsui et al. (2014), who collected the species in 2005. We confirm its presence at the type locality, an oblong forest pool of moderate depth. Individuals perched 1–3 m high on vegetation close to the pool. Males were observed to call from above and under leaves.

Intensive dip-netting of the pool revealed one Chiromantis inexpectatus tadpole. Barcoding the tadpole (ZMH A12597; Genbank accession MG909568) resulted in a 99% match with previously existing sequences (AB813160.1). The single specimen does not allow a full description of the tadpole features because of early stage (Stage 25), and damage inflicted during capture. We present here the first image of the tadpole of this species, as confirmed by genetic match with adults (Fig. 5c). The individual is 15 mm long with the tail 60.7% of the total length (tail tip damaged). The body shape in dorsal view resembles a strongly rounded rectangle. The eyes are lateral in position (cornea extend beyond body contour in dorsal view). The body is strongly pigmented with conspicuous bright white spots at the snout and dorsolaterally at the head-trunk transition. The tail is much less pigmented than the body.

Kurixalus appendiculatus (Günther, 1858): Frilled Tree Frog, Fig. 5d

Body slender; head relatively broad, triangular; snout pointed, females with pronounced snout projection; finger and toe tips broadly expanded into adhesive discs; toes webbed to three-fourth; outer fingers webbed at base; forearm and foot bear a wavy fringe of skin along outer side; series of skin projections ventrally along mandible; dorsal skin texture irregular, tuberculate; venter skin texture distinctly areolate; color above can combine brown, gray, and green with various markings, highly variable, resembling bark; throat and venter cream, ventral side of legs gray to brown; eyes large; pupil oval horizontally; iris color gold, often paler around pupil and in lower part; iris moderately reticulated; ear drum small, distinct but not set off in color from surrounding skin.—The species is probably widespread in the Maliau Basin. We encountered it in the low elevation swampy habitats at the Belian Trail areas as well as the more elevated forests around Nepenthes Camp. Males prefer to stay close to muddy forest floor depressions and often call even if such sites are not water-filled. An adult female was found at night close to the trail from Nepenthes Camp to Fawzy Waterfall sitting low on a bush.

Nyctixalus pictus (Peters, 1871) Cinnamon Frog, Fig. 5e

Medium sized, slender frog; head relatively wide, triangular and flat, snout long; canthus rostralis edged; hind limbs long; toes and finger bear round expanded discs, each disc bears two white dots; toes approximately half-webbed; dorsal skin structure spinose, spines low; dorsal coloration reddish-brown to orange, skin spines may be pale; white dots scattered over dorsal surface, flanks, and limbs; a row of white spots from snout tip to eye and along edge of upper palpebra; tympanum visible, large; eyes large; pupil rhomboid; iris white in upper sector, red in anterior, posterior, and lower sectors.—The specimen reported (photographic evidence) here was encountered at Nepenthes Camp. The species is a treehole breeder and, thus, independent of streams or ponds and might be widely distributed at MCBA. No specimen was collected.

Philautus hosii (Boulenger, 1895): Hose’s Bush Frog, Fig. 5f

Body moderately stout; head flat and broad, large eyes; snout long; canthus rostralis edged; toe and finger tips broadly expanded into adhesive discs; toes almost fully webbed; dorsal skin texture granulated, with some tubercules; tubercles can form V-shape on shoulder; skin of venter areolate; color above sandy to mid brown often with faint dark X-marking on back; scattered black spots, particularly from arm pit posteriorly; some banding on limbs; ventral side cream with pale gray-brown areas peripherally; ventral side of thighs darker, not cream; dorsolateral fold absent, supratympanic fold present, bent towards armpit and edged with dark pigmentation; iris color usually with a distinct green hue and with fine black venation; pupil horizontal, thinly edged with golden line; ear drum distinct but not set off from surrounding skin in color or skin texture.—P. hosii is a large Philautus and generally a common frog. It is most easily recognized by it’s distinctive call; males often sit several meters high in trees and can be hard to spot.

Philautus nephophilus (Dehling, Matsui & Yambun, 2016): Bush Frog 5g

Body relatively stout, but with long hind limbs; head relatively broad; snout and lower jaw arch broadly rounded; toe and finger tips expanded into adhesive discs; toes half-webbed; dorsal skin texture moderately tuberculate and granulated; dorsal color variable from olive to shades of brown with dark markings; some with X-shape pattern on mid-dorsum; limbs with banding; venter coloration brown; iris coloration golden in the dorsal sector, paler, more silvery in the lower sector and dark brown in the anterior and posterior sectors; ear drum concealed by skin.—This small species of Philautus was common around Nepenthes Camp. Among the genus, 16S data from MBCA specimens clustered closest with the 16S data provided in the original description of P. nephophilus from Kinabalu (Dehling et al. 2016, p-distance 2.5%). We regard this mild divergence (97,5% similarity) a result of isolation by distance between conspecific populations of P. nephophilus following the rationale proposed by Vences et al. (2005a, b).

Polypedates leucomystax (Gravenhorst, 1829): Four-lined Tree Frog, Fig. 5h

Body slender with long hind limbs; head relatively broad and triangular; sharp canthus rostralis; toes and fingers expanded into near circular, slightly blunt discs; toes fully webbed, except fourth; dorsal skin texture smooth (lack of tubercles) but finely granulate; ventral skin areolate; supratympanic fold present; dorsal color sandy brown to dark tan, often with four dark longitudinal stripes from head to pelvic region, plus partial dorsolateral stripe; throat, venter and parts of ventral thigh cream; throat may bear scattered darker markings; banding pattern on limbs; iris color sandy brown to amber, golden narrow edge around pupil; pupil horizontal; ear drum distinct.—This species avoids the forest and prefers open agricultural country or forest edges. It benefits from human activities and uses roadside ditches, flooded lawns, large puddles, or shallow agricultural ponds for reproduction. The species is commonly encountered and its calls heard around the Study Center area and its roads.

Polypedates macrotis (Boulenger, 1891): Dark-eared Tree Frog, Fig. 5i

Body slender with long hind limbs; head broad, rounded triangular in dorsal view; eyes big and noticeably directed forward; sharp canthus rostralis; toes and fingers expanded to broad blunt adhesive discs; not fully webbed toes; dorsal skin texture finely granular, without prominent tubercles; ventral skin of venter and thigh areolate; coloration light gray or ochre to tan above with dark spots or (sometimes) two dark stripes from snout to pelvis; area below supratympanic fold and most or all of tympanum masked in a dark brown marking that extends to flank; banding pattern on limbs; color of throat, venter and parts of ventral thigh is cream; throat and chest with some dark mottling; iris color brass to beige, with darker anterior and posterior sectors; pupil horizontal; ear drum distinct, large. —Polypedates macrotis often occurs in the same habitats with P. otilophus, such as forest clearing ponds or forest edge road ditches.

Polypedates otilophus (Boulenger, 1893): File-eared Tree Frog, Fig. 5j

Body slender to moderately robust (females); head edgy, broad, triangular; snout pointed; eyes big; saw-edged ridge above ear drum; hind limbs long, bearing distinct heel spur; fingers and toes expanded to large blunt adhesive discs; toes half webbed; color above grayish olive to yellowish light brown, fine longitudinal stripes on dorsum; thighs anteriorly and posteriorly banded with distinct zebra pattern; ventral side dirty white; ear drum visible, not embedded in dark marking; dorsal skin texture generally smooth (no prominent tubercles) but granulated above, distinctly areolate at flanks; venter skin areolate; iris beige, with fine black reticulations; pupil horizontal.—Polypedates otilophus is a species that uses clearings and forest edges for reproduction and, thus, can benefit from pond habitats created by human activities at forest edges, such as roadside ditches or village ponds. The species occurs in the vicinity of bodies of standing water at the Study Center. It is likely more widespread at Maliau Basin as the species is known to have a considerable elevational range in other regions of Borneo.

Rhacophorus borneensis Matsui, Shimada & Sudin, 2013: Borneo Flying Frog (acoustic identification; no photo)

No specimens were collected. Calls from the canopy, short in duration (approx. 1s) and composed of multiple notes of moderately high pitch in fast sequence (resembling a woodpecker) were heard at the type locality and were interpreted as calls of this species as we have know these calls from other breeding populations of this species (the original species description does not provide a call description). No recordings were made. —Rhacophorus borneensis was formerly subsumed under the name Rhacophorus reinwardtii but has recently been established as a species of its own (Matsui et al. 2013b). Matsui et al. (2014) reported R. borneensis for the Nepenthes Camp area.

Rhacophorus cyanopunctatus Manthey & Steiof, 1998: Blue-spotted Tree Frog, Fig. 5k

Body slender with long hind limbs; large eyes; pointed snout, angular in lateral view; canthus rostralis sharply edged; toes and fingers expanded into adhesive discs; toes fully webbed except fourth toe; outer fingers webbed at base, inner fingers less; dorsal skin texture granulated; supratympanic fold present; dorsal color tan to mid brown with dark brown or green blotches; white spots or a white blotch below the eye; light blue spots at the otherwise black lower flank esp. towards groin and on anterior and posterior thigh as well as ventral shank; throat and venter white to cream; horizontal pupil; iris dark amber; ear drum visible, distinct.—Rhacophorus cyanopunctatus is a species associated with riparian-vegetation, breeding in small to medium sized streams of moderate velocity. Adults perch on overhanging vegetation above the streams. R. cyanopunctatus tadpoles are stream adapted and can cling to and venture into leaf litter at the side of the stream. Their mouth is a cup-shaped sucker (Leong 2004).

Rhacophorus pardalis Günther, 1858: Harlequin Flying Frog, Fig. 5l

Body slender (males) to robust (females); head broad and flat, large eyes; hand and foot large with extensive red webbing; toes and fingers terminally expanded; heal with small skin flap; dorsal skin texture finely granulated; color above brown with dark spots or faint dark marbling and occasional white spots; lower flanks and venter with distinctive marbling in yellow/black or yellow/red, respectively; iris yellowish beige peripherally and more brown towards center; pupil oval and horizontal; ear drum visible, indistinct in color.—Among the species of gliding frogs, R. pardalis is the most widely distributed and abundant species, and seems to be tolerant of moderate habitat alterations. It is most likely to be encountered at a variety of lentic aquatic habitats. The species was present around the Study Center and Nepenthes Camp. At the forest pond at Nepenthes Camp a sample of tadpoles was collected. Identification of tadpoles was based on size, body shape, coloration, tail fin shape, and oral disk features (Inger 1966, Malkmus et al. 2002, Haas et al. 2018)