Frogs of Borneo.

Description
Feihyla kajau is a small tree frog species endemic to Borneo, distinguished by its vibrant green coloration and arboreal adaptations. Adults are relatively small, with males measuring 18 – 20 mm in snout-vent length and females slightly larger up to 22 mm. The following description is based on Inger et al. (2017) as well as the species description by Dring (1983). The body is slender with a short, pointed snout. The head wider than body. The eyes large, with horizontally elliptical pupils. Toes and fingers have discs, and toes are half-webbed with the outer fingers' webbing being around one-third. The forearms and lower legs show a wavy ridge along the outer edge. The skin is finely granulated on the back and the belly.

Dorsal life coloration is a bright, partly translucent, green with a variable amount of fine, white spots. The inner fingers and arms are white, the belly shows no pigmentation (Dring 1983, Inger et al. 2017).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Malaysia

Malaysian region distribution from AmphibiaWeb's database: Sabah, Sarawak

View distribution map in BerkeleyMapper.

Feihyla kajau is found exclusively on the island of Borneo, occurring in lowland and lower montane forests of Malaysia (Sarawak, Sabah), Indonesia (Kalimantan), and Brunei (Frost 2024). The species inhabits freshwater marsh forests, slow-flowing streams, and forest pools below 750 m a.s.l. (Inger et al. 2017).

Life History, Abundance, Activity, and Special Behaviors
Feihyla kajau is nocturnal, becoming active at dusk and remaining active throughout the night. During the day, it hides in dense foliage or under leaves to avoid predators (Dring 1983, Inger et al. 2017).

The call of the males consists of a series of high pitched double clicks (Inger et al. 2017). The dominant frequency lies between 3.5 and 5 kHz (Dring 1983).

Females lay clusters of up to 15 eggs on the underside of leaves overhanging water. Sorokin and Steigerwald (2018) showed evidence for parental egg guarding in females. After hatching, the tadpoles drop directly into the water below.

Larva
It is easy to recognize larva; they are lotic to lentic tadpole with a maximum size of 27 mm. The body is oval, wider than deep, with large eyes and nostrils, positioned dorsolaterally. The tail is comparatively long, reaching 68% of the total length. The muscular part of the tail is rather slender with the upper and lower tail fin reaching the same depth as the muscle. The oral disc is anteroventral with marginal papillae and moderately long. The tooth-row formula is: I:3 - 3/1 - 1:II (Haas et al. 2022).

Tadpoles are dorsally brown, with small bronze pigments visible. A large darker brown cross band or "saddle" is visible in the posterior part of the body. Ventral skin translucent, the organs are well visible (Haas et al. 2022).

Trends and Threats
The main threat is probably the destruction and alteration of their habitat, as they depend open primary rainforest (Inger et al. 2017).

Possible reasons for amphibian decline

General habitat alteration and loss

Comments
Feihyla kajau is a remarkable example of convergent evolution, compared to the neotropical Centrolendiae (glass frogs) family, not only in general appearance but also in reproductive behavior (Griesbaum per. comm).

References
Biju, S. D., Garg, S., Gokulakrishnan, G., Sivaperuman, C., Thammachoti, P., Ren, J., Gopika, C., Bisht, K., Hamidy, A., and Shouche, Y. S. (2020). New insights on the systematics and reproductive behaviour in tree frogs of the genus Feihyla, with description of a new related genus from Asia (Anura, Rhacophoridae). Zootaxa 4878(1), 1–55. [link]

Das, I., Hedeir, H., Pui, Y. M., Hertwig, S. T., and Haas, A. (2016). Larval external morphology and development in Feihyla kajau (Dring, 1983)(Amphibia: Anura: Rhacophoridae). Raffles Bulletin of Zoology, 64, 319-328. [download]

Dring, J. C. M. (1983). Some new frogs from Sarawak. Amphibia-Reptilia 4(2), 103–115. [link]

Frank, N., and E. Ramus (1995). Complete Guide to Scientific and Common Names of Amphibians and Reptiles of the World. Pottsville, Pennsylvania: N. G. Publishing Inc.

Frost, D. R. (2024). Feihyla kajau (Dring, 1983). Amphibian Species of the World: an Online Reference. Version 6.2. Electronic Database accessible at https://amphibiansoftheworld.amnh.org/Amphibia/Anura/Rhacophoridae/Rhacophorinae/Feihyla/Feihyla-kajau. American Museum of Natural History, New York, USA. Accessed on 29 November 2024.

Haas, A., I. Das, S. T. Hertwig, P. Bublies, and R. Schulz-Schaeffer (2022). A Guide to the Tadpoles of Borneo (eBook version). Hamburg, Germany. Tredition.

Inger, R. F., Stuebing, R. B., Grafe, U., and Dehling, J. M. (2017). A Field Guide to the Frogs of Borneo. Natural History Publications (Borneo) Limited, Kota Kinabalu.

Sorokin, A., and Steigerwald, E. (2018). Evidence for parental care in Feihyla kajau (Anura: Rhacophoridae). Phyllomedusa: Journal of Herpetology, 17(1), 127-130. [link]

Species Account Citation: AmphibiaWeb 2024 Feihyla kajau: Dring’s Flying Frog (Frank & Ramus <https://amphibiaweb.org/species/4516> University of California, Berkeley, CA, USA. Accessed Jan 30, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 30 Jan 2025.

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