Description
Raorchestes rezakhani is a small bush frog living in the Western Ghats of India. It is described from four males and no female specimens. The male range of snout-to-vent length is between 18.85 - 20.90 mm. The head is slightly more than 1.5 times wider than long. The snout is almost oval-shaped from the ventral view and is about the same length or shorter than the eye diameter. The nostrils are flapless, ovoid with dorsal compression, and nearer to the end of the snout than to the eyes. The canthus rostralis is sharply curved and the loreal region is somewhat concave. The space between the eyes is flat and longer than the distance between the nostrils, as well as the upper eyelid. The eyes are large and protruding with a horizontal pupil. The tympanum is unremarkable, and oval. It is located near the eye with a barely perceptible supratympanic fold that extends from the eye to the end of the tympanum. The dorsum is granular with small, horny spicules. Raorchestes rezakhani have one translucent vocal sac located lower on the throat. The forelimbs that are shorter than their hands. The hands lack metacarpal tubercles. Their fingers lack dermal fringe and webbing. The relative finger lengths are I < II < IV < III with each finger having only one round, weak subarticular tubercle. Supernumary tubercles are present, but indistinct. Their fingertips have round, well-developed discs with circum-marginal grooves. Raorchestes rezakhani do not have nuptial pads. Raorchestes rezakhani have long hind limbs with shanks that are shorter than their thighs and longer than their feet. The feet lack inner and outer metatarsal tubercles. The relative toe lengths are I < II < V < III < IV. Their toes have moderate webbing with a formula of I 2 - 2⁺ II 1¾ - 2⁺ III 1½ - 3 IV 2¾ - 2 − V. There is one subarticular tubercle on toes I and II, two on toes III and V, and three subarticular tubercles on toe IV. There are no supernumerary tubercles on the feet or toes. Similar to the fingers, there are well-developed, round discs on the toe tips (Al-Razi et al. 2020).

DIAGNOSIS:

Raorchestes rezakhani is comparatively smaller in size than R. amboli, R. anili, R. charius, R. chlorosomma, R. crustai, R. flaviventris, R. glandulosus, R. gryllus, R. jayarami, R. johnceei, R. kaikatti,R. kakachi, R. luteolus, R. munnarensis, R. nerostagona, R. ochlandrae, R. ponmudi, R. sahai, R. signatus, R. sushili, R. theuerkaufi, R. thodai, and R. wynaadensis. Alternatively, R. rezakhani is comparatively larger than R. garo, R. kempiae and R. shillongensis. The sub-elliptical snout in R. rezakhani differentiates it from more pointed snouts in R. annandalii, R. gryllus, R. longchuanensis, and R. tuberohumerus (Al-Razi et al. 2020). A wider than long head in R. rezakhani differentiates it from R. annandalii, R. dulongensis, R. longchuanensis, R. menglaensis, and R. shillongensis, which have either longer than wide heads or lengths and widths that are almost equal. Having a snout that is shorter than eye diameter sets R. rezakhani apart from R. sahai, and R. shillongensis, which have slightly longer snouts. Raorchestes rezakhani has nostrils that are closer to the snout than eye, which differentiates it from R. annandalii, R. garo, R. kempiae, and R. sahai, which all have nostrils that are equidistant from the eye and snout tip. Having a longer eye diameter than interorbital length differentiates R. rezakhani from R. annandalii, R. garo, R. huanglianshan, R. longchuanensis, R. malipoensis, R. menglaensis, R. sahai and R. tuberohumerus. An external single subgular vocal sac in R. rezakhani distinguishes it from the internal single subgular vocal sac in R. menglaensis. Indistinct tympanums in R. rezakhani differentiate them from R. andersoni, R. annandalii, R. dulongensis, R. garo, R. hillisi, R. huanglianshan, R. longchuanensis, R. kempiae, R. malipoensis, R. manipurensis, R. parvulus, R. sahai, and R. shillongensis. And the complete absence of metacarpal and metatarsal tubercles in R. rezakhani distinguishes it from R. annandalii, R. garo, R. longchuanensis, R. parvulus, and R. tuberohumerus, which have inner metatarsal tubercles, and R. menglaensis, which has an outer metatarsal tubercle (Al-Razi et al. 2020, Wu et al. 2021, Huang et al. 2023, please see these articles for more comparisons).

COLORATION:

The overall coloration of R. rezakhani is brown to brownish green in life. Dorsally, they are darker greyish-brown with some small dark brown spots. They also have either a black “)(” or “)-(” shaped marking on their backs. Ventrally, they are a lighter brown color than they are dorsally with small dark brown spots. Their snout, tympanum, and loreal region are a darker color than the rest of their body, and they have a black line between their eyelids. The hind limbs have multiple black bars on them, and the forelimbs have just one band. Their finger and toe discs may be whitish or reddish. The webbing on their feet is gray. Ventrally they are pale white including their vocal sacs, which are also transparent with very few small black spots (Al-Razi et al. 2020).

In preservative, most of their colors are lightened from their original state. Their backs become dark gray with brown spots instead of black spots. The tympanum and loreal region also become lighter. The bars on the limbs are retained. Both their webbing and ventrum are creamy white. The bottoms of the feet and hands are light gray and have small black specks (Al-Razi et al. 2020).

VARIATION:

Only males were collected by the species authority, so the existence of sexual dimorphism is unknown for this species. The individuals were quite similar, aside from their size and some parts of their coloration. For instance, one male was significantly smaller than the other three specimens. Also, they differed in the number of dark gray markings on their ventral surface. Lastly, on their back, three of the four individuals have a pattern that looks similar to “)(”, while the final specimen’s pattern is shaped like “)-(” (Al-Razi et al. 2020).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Bangladesh

View distribution map in BerkeleyMapper.

Raorchestes rezakhani has been found in semi-evergreen forests of northeastern Bangladesh, specifically in Lawachara National Park and Adampur, Rjkandhi Reserved Forest, Kamalgonj, Moulvibazar, mostly on the edge of streams and near man-made trails in both the primary and secondary forests. The terrain of their range is hilly, ranging 50 - 100 m in elevation. The specimens were collected at elevations of 59 and 64 meters. The annual temperatures in this range is about 9℃ in January and 32℃ from August to October, with a rainy season between May and October that provides almost 80% of the annual rainfall (Al-Razi et al. 2020).

Life History, Abundance, Activity, and Special Behaviors
Like other members of its genus, R. rezakhani are nocturnal and have direct development without free-swimming tadpoles (Al-Razi et al. 2020, Wu et al. 2021, Huang et al. 2023).

They appear to be most active during the rainy season, from April to August, during which males vocalize. They have been found on hilly slopes, vocalizing from the leaves and branches of small trees and from bamboo trunks 1.0 - 1.5 m above the ground (Al-Razi et al. 2020).

Their calls sound similar to cricket calls to the human ear. A single recorded call had a dominant frequency of 4.32 - 4.77 kHz and a duration of 16 seconds at an ambient air temperature of 27.8 °C and 97% relative humidity. The call had 25 notes, with each note lasting 0.183 - 0.379 s and having 5 - 11 pulses. Pulses had a duration of 0.003 – 0.029 s with an interpulse interval of 0.005 – 0.127 s resulting in a pulse rate of 10 – 19 per second. The internote interval was 0.222 – 0.592 s and the length of the intervals increased as the call progressed (Al-Razi et al. 2020).

Reproductive behavior was not observed in the collected specimens. However, in captivity, the closely related species R. longchuanensis was observed to lay two clutches of 10 - 12 eggs each, and the eggs hatched after 25 - 30 days (Yan et al. 2021).

Larva
Like other members of its genus, R. rezakhani is assumed to have direct development without free-swimming tadpoles (Al-Razi et al. 2020, Wu et al. 2021, Huang et al. 2023).

Trends and Threats
Currently, there is not enough information to determine whether the species is in decline. Some of the potential threats to the species include illegal logging, deforestation, and hunting, which has been known to occur even in protected areas. However, there is not enough data to confirm whether any of these are actually threatening the species (Al-Razi et al. 2020, IUCN 2022).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities

Comments

PHYLOGENETIC RELATIONSHIPS:

ETYMOLOGY

The species was named after Dr. Mohammad Ali Reza Khan who is a pioneer of wildlife research in Bangladesh (Al-Razi et al. 2020).

References
Al-Razi, H., Maria, M., and Muzaffar, S. B. (2020). A new species of cryptic Bush frog (Anura, Rhacophoridae, Raorchestes) from northeastern Bangladesh. ZooKeys, 927, 127-151. [link]

Huang, J., Liu, X. L., Du, L., Bernstein, J. M., Liu, S., Yang, Y., Yu, G., and Wu, Z. (2023). A new species of Bush frog (Anura, Rhacophoridae, Raorchestes) from southeastern Yunnan, China. ZooKeys 1151, 47–65. [link]

IUCN SSC Amphibian Specialist Group. 2022. Raorchestes rezakhani. The IUCN Red List of Threatened Species 2022: e.T178806889A194319221. https://dx.doi.org/10.2305/IUCN.UK.2022-2.RLTS.T178806889A194319221.en. Accessed on 27 February 2023.

Wu, Y.-H., Liu, X.-L., Gao, W., Wang, Y.-F., Li, Y.-C., Zhou, W.-W., Yuan, Z.-Y., and Che, J. (2021). Description of a new species of bush frog (Anura: Rhacophoridae: Raorchestes) from northwestern Yunnan, China. Zootaxa, 4941(2), 239–258. [link]

Yan, F., Liu, X., Zhang, Y., and Yuan, Z. (2021). Direct development of the bush frog Raorchestes longchuanensis (Yang and Li 1978) under laborary conditions in Southern China. Journal of Natural History, 55(1–2), 125–132. [link]

Species Account Citation: AmphibiaWeb 2024 Raorchestes rezakhani: Reza Khan's bush frog <https://amphibiaweb.org/species/9169> University of California, Berkeley, CA, USA. Accessed May 18, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 18 May 2024.

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