Raorchestes eaglenestensis, Boruah & Deepak & Das, 2025

Boruah, Bitupan, Deepak, V. & Das, Abhijit, 2025, Revision of bush frogs, Raorchestes and Philautus (Amphibia: Anura: Rhacophoridae) from the northeast Indian biodiversity hotspot with description of thirteen new species, Vertebrate Zoology 75, pp. 517-625 : 517-625

Raorchestes eaglenestensis sp. nov.

Figure 39; Tables 1, 2, S 12

Holotype.

Adult male ( WII-ADA 1619 ) collected by BB, KB and DSG on 7 July 2022 near Bompu camp ( 27.06641°N, 92.40599°E, elevation 1970 m a. s. l.), Eaglenest Wildlife Sanctuary, West Kameng District, Arunachal Pradesh, India .

Paratypes.

Eight adult males ( WII-ADA 1612 – WII-ADA 1618 , WII-ADA 1626 ) collected from the same locality and same date as the holotype by BB, KB and DSG .

Referred material.

Three adult males ( WII-ADA 1556 – WII-ADA 1558 ) collected by BB and KB on 30 June 2022 from Glow Bari ( 27.17112°N, 92.46007°E, elevation 2160 m a. s. l.), approximately 5 km north of Eaglenest Wildlife Sanctuary, West Kameng District, Arunachal Pradesh ; two adult females ( WII-ADA 2513 and WII-ADA 2514 ) and one adult male ( WII-ADA 2518 ) collected by KB on 23 August 2022 near Bompu camp ( 27.07193°N, 92.4005°E, elevation 2000 m a. s. l.), Eaglenest Wildlife Sanctuary, West Kameng District, Arunachal Pradesh .

Diagnosis.

Small sized Raorchestes, SVL 18.8–23.6 mm in adult males and SVL 21.9–22.8 mm in adult females; head length equal to width or slightly less than width in males ( HL / HW = 0.93–1.01) and head longer than wide in females ( HL / HW = 1.07); vomerine teeth absent; snout rounded to sub-oval, its length slightly less than or equal to eye length ( SL / EL = 0.85–1.0); nuptial pad present on first finger; blunt tubercles on top of head, upper eyelid, dorsum and dorsal surface of limb; pair of olive brown, concave stripes on dorsum; a broad brown crossbar on forearm; three crossbars on thigh and tibia.

Description of the holotype.

Holotype is well preserved except for an incision on underside of right thigh. Snout-vent length 22.1 mm; head slightly wider than long; depression on dorsal aspect of snout between internasal region and snout tip; snout rounded in dorsal view and nearly acute in lateral view, slightly protruding beyond lower jaw, blunt tubercular projection on snout tip; its length less than eye length ( SL / EL = 0.9); canthus rostralis rounded, obliqued; loreal region concave; nostril oval, laterally positioned and obliquely oriented; nostrils equally positioned between eye and snout tip; eye moderate in size, length less than half of head length ( EL / HL = 0.41); tympanum round, distinct, nearly one third of the eye length ( HTYD / EL = 0.29); supratympanic fold distinct; internasal distance less than inter-upper eyelid width ( IN / IUE = 0.85) and greater than upper eyelid width ( UEW / IN = 0.7); choanae oval; vomerine teeth absent; tongue posteriorly notched and posterior lobe on right side shorter than lobe on left side; pair of slit like openings present on lower jaw; trunk dorso-ventrally flattened, slender, half of snout-vent length ( AG / SVL = 0.51).

Forelimbs slender, forearm shorter than hand length ( FAL / HAL = 0.72); relative length fingers = I <II <IV <III; finger with rounded disc; circum-marginal groove on disc present; disc of the fingers II – IV wider than tympanic diameter; webbing absent; subarticular tubercles rounded and enlarged except the proximal subarticular tubercle on third and fourth finger which smaller and indistinct; subarticular tubercles on fingers I: II: III: IV = 1: 1: 2: 2; palmar tubercles not visible; finger without lateral dermal fringe; fine granular nuptial pad present on base of first finger covering inner lateral and dorsal surface, supernumerary tubercles absent.

Hindlimbs slender, thigh length half of the snout-vent length ( TL / SVL = 0.5); relative length toes = I <II <III <V <IV; tibia length equal to thigh length and longer than foot length ( FOL / TBL = 0.84); toe with rounded disc; disc width equal to those of fingers; circum-marginal groove present; subarticular tubercles rounded, proximal subarticular tubercles on toe III – V smaller and indistinct; indistinct inner metatarsal tubercle present; outer metatarsal tubercle absent; supernumerary tubercles absent; no dermal fringe along toe V; webbing slight, reaching below second subarticular tubercle of fourth toe.

Smooth skin on dorsal aspect of snout, upper eyelids and head; three tubercles in a longitudinal straight line on middle of head; indistinct tubercles on upper eyelid; few prominent tubercles on mandibular region behind angle of jaw; tubercles scattered dorsal to supratympanic folds, on dorsum and spreading to flank; tubercles absent on posterior part of dorsum; forelimb and hindlimb smooth dorsally; tubercles on limb not visible as in life condition; throat, chest, ventral aspect of forelimb and tibia smooth; abdomen granular, indistinct; granules on thigh barely visible.

Colouration in life.

Dorsal surface of head, dorsum and limbs pale reddish brown; upper eyelids pale grey; lateral aspect of head pale-greyish with reddish tinge; iris dark brown, speckled with golden, heavily speckled dorsally; inverted triangular patch on dorsal surface of head covering inter-upper eyelid space and posterior part of head; a broad “ X ” shaped, olive-brown coloured pattern on dorsum; indistinct cross bar on forearms; similar bars on dorsal surface of hand and outer two fingers; three broad crossbars on thigh and tibia; similar bars on dorsal surface of foot and outer three toes; disc on inner two fingers and inner three toes yellow, rest of the discs reddish with brown mottling; on ventrum, head, abdomen and limbs flesh-coloured with brown mottling; enlarged white blotches on chest and abdomen; lateral side of thigh pale-reddish.

Colouration in preservative.

Dorsal surface of snout and lateral aspect of head pale brown; slightly dark brown stripe on loreal region; upper eyelids dark grey; large dark brown patch on head; dark brown spots on upper jaw, below eyes to mandibular region; posterior part of head to anterior part of dorsum pale yellowish brown, posteriorly dorsum slightly darker; a “ X ” shaped dark brown mark on dorsum, its anterior ends starts from posterior corner of upper eyelid, posterior ends broader and directed towards groin; forelimbs pale yellowish brown, a broad brown cross bar on forearm; irregular sized, brown patches on top of hands and two outer fingers; hindlimb pale yellowish brown; three broad crossbars on each thigh and tibia; similar bars on tarsus and foot and outer three toes; an enlarged dark brown patch on vent area; throat, chest, abdomen, ventral aspect forelimb and hindlimb pale cream coloured with brown mottling.

Sexual dimorphism and morphological variation.

In males head length equals to width or slightly smaller than width vs. head longer than head width in female; a subgular vocal sac present in males; a pair of internal vocal sac openings present on lower jaw and a nuptial pad present in males. Snout shape varies among the individuals from rounded to sub-oval; in some individuals, a white bar on head connecting the upper eyelids was observed; irregular shaped and sized yellow spots present on head, back and limbs present in some individuals. Morphometric variations are provided in Table S 12.

Morphological comparison.

Raorchestes eaglenestensis sp. nov. differs from R. annandalii by snout length being smaller than or equal to eye length (vs. snout length greater than or equal to eye length); it differs from R. barakensis sp. nov. by absence of extra bone on humerus (vs. an extra bone present on humerus); it differs from R. boulengeri sp. nov., R. mawsynramensis sp. nov., and R. orientalis sp. nov. by presence of distinct tubercles on dorsum (vs. dense spinules on dorsum); it differs from R. cinerascens nov. comb. by absence of enlarged dark and light patches on groin (vs. spot partially encircled by yellow tinge on groin); it differs from R. dibangensis sp. nov. by presence of distinct bunt tubercles on dorsum (vs. dense spinules on dorsum), presence of three broad crossbars on thigh and tibia (vs. two indistinct crossbars on thigh and tibia); it differs from R. dulongensis by presence of nuptial pad on first finger (vs. nuptial pad absent); it differs from R. garo by absence of dark brown patches on groin and thigh (vs. present), dorsum with blunt tubercles (vs. dorsum with spinules); it differs from R. hekouensis , R. hillisi and R. malipoensis by larger body size, SVL 18.8–23.6 mm in adult males (vs. 16.1–17.5 mm in R. hekouensis , 15.9–17.7 mm in R. hillisi and 14.6–17.7 mm in R. malipoensis ); it differs from R. huanglianshan , R. menglaensis , and R. tytthus nov. comb. by snout length being equal to or less than eye length (vs. snout length longer than eye length); it differs from R. jadoh by larger body size in adult males, SVL 18.8–23.6 mm (vs. SVL 13.6–14.0 mm), and by inter-upper eyelid width being less than or equal to eye length (vs. inter-upper eyelid width greater than eye length); it differs from R. jakoid by snout length being less than or equal to eye length (vs. snout length greater than eye length); it differs from R. khonoma sp. nov. by presence of three crossbars on thigh and tibia (vs. single crossbar on thigh and tibia), presence of distinct “ X ” mark or concave stripes on dorsum (vs. stripes on dorsum barely visible), presence of tubercles pronounced on head and dorsum (vs. tubercles on head and dorsum comparatively small and more sparsely distributed), and absence of brown and white patch on groin (vs. brown and white patches on groin present); it differs from R. lawngtlaiensis sp. nov. by internarial distance being greater than upper eyelid width (vs. internarial distance equal to upper eyelid width); it differs from R. leiktho by larger body size in adult males, SVL 18.8–23.6 mm (vs. SVL 15.7–15.8 mm); it differs from R. longchuanensis , R. yadongensis by inter upper eyelid width being equal to eye length (vs. inter upper eyelid width greater than eye length); it differs from R. menglaensis by snout length being equal to or smaller than eye length (vs. snout length longer than eye length); it differs from R. mindat by absence of black or white patches on groin (vs. enlarged black and white patches present on groin), absence of white patches on the lateral aspect of thigh (vs. enlarged white patches on lateral aspect of thigh); it differs from R. monolithus sp. nov. by the distinct “ X ” mark or concave stripes on dorsum (vs. stripes on dorsum barely visible), tubercles pronounced on head and dorsum (vs. tubercles on head and dorsum comparatively small and more sparsely distributed), and absence of brown and white patch on groin (vs. light brown and white patches on groin present); it differs from R. nasuta sp. nov. by rounded or sub-oval shaped snout (vs. snout acute); it differs from R. narpuhensis sp. nov. by presence of three crossbars on thigh and tibia (vs. single cross bar on thigh and tibia); it differs from R. parvulus by presence of three crossbars on thighs (vs. single cross bar on thigh); it differs from R. rezakhani by absence of dark pattern on groin (vs. a short brown streak present on groin); it differs from R. shillongensis by presence of three broad crossbars on thigh and tibia (vs. single broad crossbar on thigh and tibia). A detailed morphological comparison with its congeneric species is provided in Table 1. Morphological characters of R. eaglenestensis sp. nov. and R. kempiae are similar but they have minor overlap in morphospace (Fig. 6 C ). Raorchestes kempiae is restricted to south of Brahmaputra Valley while R. eaglenestensis sp. nov. is restricted to north of Brahmaputra Valley.

Acoustics.

The calls of R. eaglenestensis sp. nov. were recorded in Glowbari, near Eaglenest Wildlife Sanctuary on 30 June 2022 at 20: 10 hrs and at an ambient temperature of 21.4 ° C; in Bompu, Eaglenest Wildlife Sanctuary on 7 July 2022 at 20: 00 hrs and at ambient temperature of 21.1 ° C. The call description is based on 60 calls including two individuals ( WII-ADA 1558 and WII-ADA 1619 ). The calls are single type, non-pulsatile, emitted in groups (2–4 calls per group) in regular intervals (Fig. 40 ). The mean call duration is 16.3 ± 1.74 ms (9–20 ms) with call rise time of 1 ms and call fall time of 15.45 ± 1.7 ms (12–18 ms). The mean inter-call interval is 236.56 ± 8.89 ms (224–270 ms). The mean dominant frequency is 3029.73 ± 61.33 Hz (2971.6–3100.8 Hz). A detailed comparison of advertisement calls with those of congeners is summarised in Table 2.

Phylogenetic relationships and genetic divergence.

Phylogenetically R. eaglenestensis sp. nov. was recovered as a basal lineage to a large clade containing R. hillisi group, R. kempiae group, R. rezakhani group, and R. garo group in ML analysis with weak support ( UFB <50) and in BI analysis it nested with hillisi group with weak support ( PP <0.5; Figs 2 , 3 ). The genetic divergence of R. eaglenestensis sp. nov. with the other members of the genus varies between 2.9–8.0 % in the 16 S, 9.1–19.1 % in the cyt b and 7.3–15.4 % in the COI genes (Table S 7 A – C).

Etymology.

The specific epithet is a toponym derived from the name of the “ Eaglenest Wildlife Sanctuary ” in the State of Arunachal Pradesh where the type specimens were collected.

Suggested common name.

Eaglenest Bush frog.

Distribution and natural history.

Raorchestes eaglenestensis sp. nov. is currently known only from the Eaglenest Wildlife Sanctuary and adjacent areas such as Glow Bari within an elevation range of 1950–2200 m a. s. l. (Figs 25 B , 33 F ) We recorded the individuals on hill slopes along forest trails; in the months of June and July. Calling males were observed on ferns, bamboo and shrubs at a height of 0.5–2 m above ground. Other amphibian species recorded at this locality include Nasutixalus sp. , Xenophrys sp. Amolops wangyali Mahony et al., 2022 , Amolops sp. , Rhacophorus burmanus (Andersson, 1939) , Leptobrachium bompu , Duttaphrynus himalayanus (Günther, 1864) , Nanorana liebigii (Günther, 1860) and Nanorana sp. Athreya (2006) reported several morphs of unidentified Raorchestes sp. (as Philautus sp. ) from Eaglenest Wildlife Sanctuary and suggested that it had at least four different calls. Athreya (2006) did not provide details of the locations and acoustic parameters for comparison. However, some of the photographs of Philautus sp. provided in Athreya (2006) falls within the morphological variation of R. eaglenestensis sp. nov.

Figures

Figure 2. A, B Maximum likelihood tree inferred from the concatenated data set (16 S, cyt b, COI and RHO) for Raorchestes species from northeast India, Indo-Burma and Indo-China. Outgroups are not shown in this tree. Numbers at the internal branches represent ultrafast bootstrap values (UFB). Values below 50 are not shown. Scale bar: substitutions per site.

Figure 3. A, B Bayesian tree inferred from the concatenated data set (16 S, cyt b, COI and RHO) for Raorchestes species from northeast India, Indo-Burma and Indochina. Outgroups are not shown in the tree. Numbers at the nodes represent posterior probability (PP) value. Values <0.5 are not shown. Scale bar: substitutions per site.

Figure 6. Principal Component Analysis (PCA) of 176 specimens of Raorchestes using 38 morphometric characters (A – D). A Raorchestes garo group, B Raorchestes rezakhani group, C Raorchestes kempiae group + R. khonoma sp. nov. + R. eaglenestensis sp. nov., D Raorchestes annandalii group + R. mindat + R. arunachalensis sp. nov. + R. magnus sp. nov. Sister species plotted with same symbols but with different colours. E PCA of R. garo and R. kempiae specimens using eight morphometric characters.

Figure 25. Distribution of Raorchestes species in northeast India. A Raorchestes rezakhani and four other closely related species; B Raorchestes annandalii and three new species. Type localities are denoted by stars, and other localities are denoted by circles.

Figure 33. Habitat at the type localities of Raorchestes species in northeast India. A Lowland forest stream at the type locality of R. lawngtlaiensis sp. nov. in Ngengpui WLS; B landscape view of Mehao WLS from Abango, type locality of R. dibangensis sp. nov. in Abango; C. hill stream and riparian habitat at the type locality of R. shillongensis in Malki, Shillong; D landscape view of the hills at Pumdunlong, the type locality of R. monolithus sp. nov. at Willong Khullen Village; E landscape view of hills and lowland areas at Khonoma, the type locality of R. khonoma sp. nov.; F forest cover at Bompu, Eaglenest WLS at the type locality of R. eaglenestensis sp. nov.; G hill stream and forest cover at Abor hills, habitat of R. magnus sp. nov.; H landscape view of Abor hills and adjacent lowland areas, habitat of R. arunachalensis sp. nov.

Figure 39. Raorchestes eaglenestensis sp. nov. A Dorsal and B ventral view of holotype (WII-ADA 1619) in preserved condition. C Dorsal view of WII-ADA 2514 in preserved condition. D – G Holotype in life, D dorsolateral view, E ventral view, F groin, G posterior view of thigh. H WII-ADA 1556 in life; I paratype (WII-ADA 1615) in life; J, K two uncollected males from Bompu, Eaglenest Wildlife Sanctuary. Scale bar = 10 mm.

Figure 40. Comparative spectrograms and oscillograms illustrating representative calls of two new species of Raorchestes. A, B Oscillograms, C spectrogram, D power spectrum. The call marked with an arrow on top in A is expanded in B.