Bioacoustics of Xenophrys oropedion

Diagnosis. Megophrys oropedion sp. nov. is diagnosable from geographically relevant congeners by the following combination of characters: small-sized, robust species, adult-male SVL 32.8–39.2 mm (N=7), adultfemale SVL 44.1–48.7 mm (N=2); HW≥HL, HW/SVL 33.9–38.5% (N=9); tympanum clearly defined, TYD /ED 53.7–69.0% (N=9); SHL/SVL 41.7–48.4% (N=9), mean male SHL/SVL 45% (N=7), mean female SHL/SVL 42.1% (N=2); vomerine ridges ovoid, with vomerine teeth present; subarticular, inner and outer palmar tubercles and inner metatarsal tubercles absent in life and in preservation; digit tips not expanded relative to digit width; webbing and lateral fringes on toes absent; dorsolateral folds always present, approximately 75 percent of trunk length; distinct “X”-shape marking on dorsum absent; protruding projection posterior to cloaca of males absent; single dominant frequency range of male advertisement call at 3,100–4,250 kHz, with maximum note energy of between 3,364–3,527 kHz (3,388±70 kHz) at 18°C ( Figure 7 ). Comparisons. Megophrys oropedion sp. nov. differs from the following large-sized species by considerably smaller adult-male size, SVL 32.8–39.2 mm , N=7 (vs. adult-male SVL> 53 mm : M. gigantica , N=6; M. glandulosa , N=10; M. jingdongensis , N=2; M. lekaguli , N=8; M. major , N=8; M. medogensis , N=16; M. omeimontis , N=10; M. robusta , N=4; M. spinata , N=2); from the following medium-sized species by smaller adultmale size, SVL 32.8–39.2 mm , N=7 (vs. Megophrys ancrae sp. nov. male SVL 39.1–45.0 mm, N=8; M. binlingensis SVL 45.1–51.0 mm, N=3; M. megacephala SVL 45.9–53.4 mm , N=7; M. takensis SVL 47.3–53.0 mm, N=3), further from Megophrys ancrae sp. nov. by HW≥HL (vs. HL>HW), digit tips not expanded terminally (vs. digit tips distinctly expanded terminally), small sharp horn-like tubercle absent on the eyelids (vs. present on most individuals), further from M. binlingensis by lateral fringes on toes absent (vs. present), further from M. megacephala by considerably narrower head HW/SVL 33.9–38.5%, N=9 (vs. HW/SVL 40.2–45.1%, N=9), and further from M. takensis by vomerine ridges ovoid (vs. elongated stalk-like projections); from the following smallsized species by larger adult size, male SVL 32.8–39.2 mm , N=7, female SVL 44.1–48.7 mm , N=2 (vs. M. wuliangshanensis male SVL 27.3–31.6 mm , N=10, female SVL 41.0– 41.5 mm , N=2; M. zunhebotoensis male SVL 30.0 mm, N=1, female SVL 39.0 mm, N=1), further from M. wuliangshanensis by larger tympanum on males, mean TYD /ED 60.4%, N=7 (vs. mean male TYD /ED 48.8%, N=10), considerably shorter mean shank length, mean male SHL/SVL 45%, N=7, mean female SHL/SVL 42.1%, N=2 (vs. mean male SHL/SVL 50.5%, N=10, mean female SHL/SVL 50.4%, N=2), and further from M. zunhebotoensis by male SHL/SVL 43.4–48.4%, N=7, female SHL/SVL 41.7–42.6%, N=2 (vs. male SHL/SVL 50%, N=1, female SHL/SVL 46.1%, N=1); from M. nankiangensis and M. shapingensis by presence of clearly defined tympanum (vs. tympanum concealed by supratympanic fold); from M. binchuanensis and M. wushanensis by subarticular tubercles absent (vs. present), and lateral fringes on toes absent (vs. present); from M. minor by HW≥HL (vs. HL>HW), vomerine teeth present (vs. absent), differences in male advertisement call characters, note duration 30–55 ms (44.6±7.33 ms, N=32) and a single primary frequency range at 18°C (vs. note duration 74.6–110.1 ms [90.8±12.6 ms, N=14], and a second subdominant frequency pulse at 6,800–7,600 kHz at 14°C); from M. palpebralespinosa by webbing between toes absent (vs. approx. half digit length); from M. daweimontis by inner and outer palmar tubercles and inner metatarsal tubercles absent in life and in preservation (vs. distinct and red in colour), SHL/SVL 41.7–48.4%, N=9 (vs. SHL/SVL 53.7% on holotype ); from M. wawuensis and M. zhangi by distinct “X”-shape marking on dorsum absent (vs. present) and dorsolateral folds distinct (vs. indistinct), further from M. wawuensis by larger tympanum, TYD /ED 53.7–69.0%, N=9 (vs. TYD /ED ca. 33%), and further from M. zhangi by lateral fringes on toes absent (vs. present); from M. pachyproctus by protruding projection posterior to cloaca of male absent (vs. present); from M. parva by larger adult female size, SVL 44.1–48.7 mm , N=2 (vs. female SVL 41.1–41.4 mm , N=2), larger tympanum TYD /ED 53.7–69.0%, N=9 (vs. TYD /ED 40.0–48.9%, N=4), and digit tips not expanded relative to digit width (vs. digit tips noticeably expanded relative to digit width); from M. serchhipii by dorsolateral folds always present, approximately 75 percent of trunk length (vs. absent).

Distribution. This species is confirmed here from Malki Forest ( 1,520–1,600 m asl.), Shillong, and Mawphlang Sacred Forest ( 1,810 m asl.), Mawphlang village, both in the East Khasi Hills district of Meghalaya state, northeast India ( Figure 3 ). It has also been observed, but not collected from North East Hill University (NEHU) ( 25°36.767’N 91°45.050’E , 1,410 m asl.), on the outskirts of Shillong city (SM pers. obs.). This species is likely to be found in other forest fragments in the East and West Khasi Hills districts that cover the upper reaches of the Shillong Plateau above 1,400 m asl. Habitat and natural history. The forest type around Shillong and Mawphlang is categorized as subtropical wet hill forest (Champion & Seth 1968). The forest at the type locality is dominated by pine ( Pinus kesiya Royle & Gordon ) plantation, with a considerable amount of broadleaf trees lining the stream banks (SM, pers. obs.) ( Figure 4B ), while the forest at Mawphlang is dominated by broadleaf trees ( Figure 4C ). The collection streams at these localities were approximately 1–3 m wide and 10–40 cm deep, of moderate flow on a slight incline, primarily rocky with intermittent gravel bed, and with quiet pools that accumulate detritus, branches and leaf litter (for further details on habitat at Mawphlang see Mahony [2008]). The species was only found along portions of the streams that experience low levels of human disturbance. One female was collected on a trail ca. 200 m from the nearest stream, and another collected from a trail nearby a stream. Males were collected from the lower branches of bushy vegetation at ca. 20 cm above ground level, within 2 m from the edge of streams, or from rocks on the stream banks. One uncollected male was located inactive during day time in a fallen hollow branch lying over a stream ( 1 m above stream level). Metamorphosing juveniles were found during May and June at Shillong and Mawphlang. Males began calling vigorously from dusk until late into the evening (18:00 until at least 23:30 h), regardless of precipitation level, but more intensely during light rain and/or when cloud cover envelops the forest, when regular calling began as early as 16:00 h, but was reduced during heavy precipitation. Calling was observed during visits between 20th May to 15th September . Sporadic daytime calling was heard on both overcast and clear days at Shillong and Mawphlang, and it consisted of one to two call repetitions followed by extended silence, usually from unobserved calling sites within dense bushes. Calling males distanced themselves from others by a minimum of 1 m of stream bank and distinctive territorial calls were emitted when males were played back their call at close quarters, as noted in other species (Mahony & Reza 2008). The advertisement call of Megophrys oropedion sp. nov. was recorded from two individual males (not collected) from the banks of the Um Risa stream within meters of the collection locality of the holotype . These individuals were photographed in-situ and released, and match the type series in all general external morphological characters. The call consists of a single pulsed note of 30–55 ms duration (44.6±7.33 ms, N=32), containing 6–10 pulses per note (7.7±0.97, N=32). Pulse intervals gradually decrease from the beginning to the end of the note. Amplitude modulation within notes is apparent, beginning with moderately high energy pulses, increasing slightly to a maximum by approximately mid note, and subsequently decreasing rapidly towards the end of each note. Calls are repeated in series at a rate of 3–4 per second, with an irregular call interval of 108–415 ms duration (276±67 ms, N=32). Duration of call series was not recorded, but calls were continuously emitted throughout the longest recording made of 24 s. Calls had a single dominant frequency range of 3,100–4,250 kHz with the maximum note energy varying from 3,400–3,500 kHz (3,388±70 kHz, N=27). Out of a total of 18 metamorph to adult frogs photographed, two examples with eye deformities were observed (not collected), one from Mawphlang and the other from the lower Malki forest. In both cases, one eye was smaller than the other, with the pupil off-center and partially obscured by the upper eyelid. It was not tested at the time of observation whether the deformed eyes were functional. At both of these localities, the breeding streams are intensively used as clothes-washing areas and in such sections of the streams the rocks are covered with a grey slime from excessive detergent use and calling males are absent (see Mahony 2008 for further discussion). Whether detergent use in these streams is responsible for causing the malformations, or whether it is a result of natural parasite/viral infection or trauma should be further investigated.