Description
Rhacophorus malkmusi has a relatively small body with a snout-vent length of 32.2 - 35.4 mm in females and 26.4 - 29.3 mm in males. It’s moderately slender body narrows from temporal region to groin. The head is short and wider than it is long. From the dorsal view, the snout is obtuse and rounded while in the lateral view it projects beyond the mandible and is sub-truncated. The canthus rostralis is distinct and slightly curved when viewed from the profile while concave when viewed dorsally. The slightly protruding and dorsolaterally-oriented nostrils are closer to the tip of snout than to the eye and separated from each other by a greater distance than to the eyes. The loreal region is oblique. The anterolaterally-directed eyes are large and protruding with horizontal pupils. The eye diameter is greater than the distance between the eye and the nostril. The interorbital distance is both greater than the upper eyelid width and the internarial distance. The frontoparietals are domed and form little humps between the eyes. The tympanum is distinct, circular, and about a third the size of the eye diameter. There is a weak supratympanic fold. He skin on the head is not co-ossified to the skull. The dorsal surfaces of the head and body as well as the chin, throat, and chest are smooth. The abdomen and ventral sides of thighs and infra-anal region are granulated. There is a weak supracloacal fold above the vent that is attached on the distal end. The arms are moderately slender with a small row of tubercles along the post-axial edge of the forearm. The relative finger lengths are I < II < IV < III and end in enlarged oval discs on fingertips with circummarginal grooves. The disc of finger III is as wide as the tympanum. The fingers are webbed with a formula of I₂ - ₂II_1.75 - ₃III₂ - ₂IV and narrowly fringed on the postaxial edge of finger IV between the proximal end of the disc and the palmer tubercle. The well-developed subarticular tubercles are rounded, appearing singularly on fingers I and II and paired on fingers III and IV. The distal subarticular tubercles on the last two fingers are as big as the subarticular tubercles of the first two fingers and larger than the proximal subarticular tubercles. The large thenar tubercles is oval while the palmar tubercle is very small. There are several small supernumerary tubercles on the metacarpals. Its legs are slender, moderately long, and have a large conical tubercle on the tibio-tarsal articulation as well as many small tubercles on the postaxial edge of the tarsus. The heels overlap when knees are flexed with thighs perpendicular to the plane of its body. The tips of the toes have enlarged with oval discs with circummarginal grooves but are not as large as the discs on fingertips. The relative toe lengths are I < II < III < V < IV and the webbing formula is I_1⁺ - ₂II₁ - _2.25III_1.5 - ₃IV_2⁺ - _1⁺V. There are fringes in the post-axial edge of toe V from the proximal end of the disc to the base of the metatarsus. The small inner metatarsal tubercle is oval and there is no outer metatarsal tubercle (Dehling 2015).

Rhacophorus malkmusi can be distinguished from all other South East Asian species of the genus Rhacophorus by a few key features. It has a relatively short snout-vent length (see description above) with a head that is wider than long and wider than the body. It has low, short vomerine ridges that run between choanae. Along the forearm is a row of small white tubercles without a dermal flap. There is webbing on both sides of the third finger and toe. More specifically, R. malkmusi is most like R. granui from which it was split. The two species can be differentiated because R. malkusi does not have a large, pointy tubercle on the upper eyelid, has small teeth on its vomerine ridges, has a larger interorbital distance, has a shorter head, has a more stub-like snout, has an oblique loreal region, has a small thenar tubercle, and has weaker digit webbing (however, R. granui has highly variable finger webbing and may have a finger with less webbing than R. malkusi's standard formula). Rhacophorus malkmusi is also similar to R. bimaculatus, R. belalongensis, and R. gadingensis. However R. malkmusi can be differentiated because the latter three have longer heads and blue spots on their flanks. Rhacophorus malkmusi can be further differentiated from R. bimaculatus and R. gadingensis because the latter two do not have vomer ridges or teeth. Additionally, Rhacophorus malkmusi can be further differentiated from R. belalongensis and R. gadingensis because the later two have more extensive webbing on the toes and they have shorter interorbial distances. Lastly, the advertisement call of all four species is similar in that they all comprise of 1 – 3 short clicks, but R. malkmusi can be differentiated from R. belalongensis, the only other one analysed, by the latter having a higher frequency of 5800 Hz and longer duration of 70 milliseconds (see Life History for more specifics on R. malkmusi's call; Dehling 2015).

In life, R. malkmusi has an ochre dorsal coloring during the day and light brown at night. The dorsum is patterned with many, evenly spaced, small dark dots and several large, irregularly shaped dark brown spots. Between the eyes and extending to the margins of the upper eyelids is a narrow, dark brown, interorbital band. On each sides of the head is an irregular, large, white infraorbital spot surrounded by a thin dark brown line. There are two smaller white spots below the tympanum. There are crossbars on the dorsal sides of arms and legs that turn from greyish during the day to dark brown at night. The tubercles on the limbs are white. The groin area, anterior and posterior sides of the thighs, ventral sides of the lower leg, anterior side of the foot, and the tops of toes I and III are bright yellow. The other toes are white as is the throat and venter. The ventral surface of the limbs is unpigmented. The ventral surfaces of the hands and feet are brown. The webbing of the digits is greyish. The iris is ruby and lightens to yellow at the margins with a black rim along the outer edge. In preservation, dorsal coloration fades to light grey and all the dark dorsal markings become faintly visible except the interorbital band, which remains distinct. The yellow regions fade but are still visible. The iris becomes bluish grey and the dermal calcars appear shriveled but still apparent (Dehling 2015).

Females have more brown coloration in preservative while males are more grey (Dehling 2015).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Malaysia

View distribution map in BerkeleyMapper.

The species is common at its type locality of Sungai Langanan and the nearby Poring Hot Springs, on the Eastern slope of Gunung Kinabalu. It has also been found on the foothills of the Crocker Range and near Kemabong/Sipitang in the southwest Sabah region. It is assumed to live in other mountain ranges of western Sabah. The species is found near rivers from which their mating system relies on. The holotype was collected at 750 meters above sea level (Dehling 2015). The species of this genus prefer low elevations, and are most likely to live 180 - 900 meters above sea level (Sheridan et al. 2012).

Life History, Abundance, Activity, and Special Behaviors
Female type specimens were found away from streams in August, the end of the dry season, and were not in reproductive condition. In November, the rainy season, males were found calling from overhanging leaves, 1.5 – 4 meters high, and fresh foam nests were found between 1.5 and 2.5 meters above water (Dehling 2015).

Eighteen advertisement calls from four males were recorded at 21^oC. The calls were produced at irregular intervals lasting between 28 seconds to several minutes and consisted of 1 – 3 very short click notes with a duration of 10 – 36 milliseconds and an energy maximum of 4650 – 5400 Hz. When more than one note was in a call the interval between notes lasted 55 and 168 milliseconds and the notes differed by 50 – 400 Hz. The prominent harmonics were recoreded at 15,000 Hz (Dehling 2015).

Trends and Threats
Specific threats to R. malkmusi are currently unidentified, however similar species of the genus are threatened by habitat loss and climate change. The conversion of forests to oil palm plantations is an increasing trend in the South East Asian biodiversity hotspots, including the low land of Borneo, the home of R. malkmusi and many other vulnerable amphibian species. This deforestation combined with climate change poses threats to biodiversity of the region (Sheridan et al. 2012).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Habitat fragmentation
Local pesticides, fertilizers, and pollutants
Predators (natural or introduced)
Climate change, increased UVB or increased sensitivity to it, etc.

Comments
The species authority is: Dehling, J. M. 2015. A new species of Rhacophorus (Anura: Rhacophoridae) from Gunung Kinabalu, Borneo. Salamandra 51: 1–11

Rhacophorus malkmusi was placed into this genus based off of its similar morphological characteristics to other species of the genus Rhacophorus. It was split from R. granui (Dehling 2015).

The species epithet, malkmusi, is in honor of Rudolf Malkmus’ contributions to the knowledge of the amphibians of Gunung Kinabalu (Dehling 2015).

References

Dehling, J. M. (2015). ''A new species of Rhacophorus (Anura: Rhacophoridae) from Gunung Kinabalu, Borneo.'' Salamandra , 51(1), 1-11.

Sheridan, J. A., Howard, S.D., Yambun, P., Rice, J.L., Cadwallader-Staub, R., Karoulus, A., Bickford, D (2012). ''Novel Behaviors of Southeast Asian Rhacophorid Frogs (Anura, Rhacophoridae) with an Updated Anuran Species List for Danum Valley, Sabah, Malaysian Borneo.'' Tropical Natural History, 12(1), 1-8.

Species Account Citation: AmphibiaWeb 2016 Leptomantis malkmusi <https://amphibiaweb.org/species/8386> University of California, Berkeley, CA, USA. Accessed Feb 3, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 3 Feb 2025.

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