Bioacoustics of Rhombophryne nilevina

Definition. Within the R. laevipes group, this species forms a subclade with R. botabota , R. sonaliae sp. nov . and R. anatiala sp. nov . (described below) based on molecular phylogenetic data (Fig. 2 ; Belluardo et al. 2022 ). It is characterised by the possession of the following unique suite of characters: (1) large body size, adult SVL 41.2–57.2 mm ; (2) head wider than long ( HW / HL 1.42–1.81); (3) moderately small eyes ( ED / HL 0.31–0.34); (4) relatively long hindlimbs ( HIL / SVL 1.52–1.83); (5) small inner metatarsal tubercle ( IMTL / FOL 0.10–0.14); (6) outer metatarsal tubercle absent; (7) second finger distinctly shorter than fourth; (8) third toe distinctly longer than fifth; (9) dorsal skin smooth; (10) absence of chin barbels; (11) absence of pronounced superciliary spines; (12) presence or absence of white inguinal spots on a blackish background; (13) presence or absence of white spots on the posterior thigh and ventral shank; (14) unfortified skull without expansion of maxilla or posterior process of angulosplenial; (15) clavicles present, thin, curving; and (16) advertisement call (based on 7 analysed calls by one individual) pulsed, with (17) call duration 538–598 ms, (18) inter-call interval 42–126 s, and (19) dominant frequency 526–534 Hz. Rhombophryne nilevina is furthermore distinguished from all other Rhombophryne species analysed by the following robust diagnostic nucleotide combination in the mitochondrial 16 S rRNA gene (positions relative to the full 16 S sequence of Anilany helenae MZ 751042 ): in 16 S 5 ’, ‘ G’ at site 389, ‘ T’ at site 401, and ‘ T’ at site 555; in 16 S 3 ’, ‘ T’ at site 956, ‘ T’ at site 1075, ‘ A’ at site 1131, and ‘ A’ at site 1157.

Call. The advertisement call recorded on 8 February 2015 (12: 00 h) near Andemaka, Ranomafana National Park (air temperature estimated to be around 20 ° C; presumably emitted by the holotype KU 340897), consists of a pulsed note of moderate to long duration, emitted at irregular and long intervals. Calls (= notes) exhibit distinct amplitude modulation, with call energy starting at low level, moderately increasing to about one fourth of the call’s duration, rapidly increasing after half of the call’s duration, reaching its maximum in its last quarter, followed by a decrease towards the call’s end. The second half of the call is characterized by a short intermittent drop in call energy. Pulses are very narrowly spaced in the second half of the call and very short in duration, with each pulse being apparently shorter than 2 ms, but almost impossible to measure exactly. In the first half of the call, pulses are longer in duration (ca. 9 ms) and repeated less rapidly. It is not possible to count the number of pulses per note (= call), but pulse repetition rate can roughly be calculated for each section of the note. Numerical parameters of 7 analysed calls are as follows: call duration (= note duration) 538–598 ms (561 ± 21 ms); inter-call intervals rather long and irregular, varying from 42–126 s (81 ± 41 s); pulse repetition rate within first half of the call 100 pulses / second, within second half of the call approximately 260–270 pulses / second; dominant frequency 526–534 Hz (530 ± 3 Hz); prevalent bandwidth 250–4500 Hz; numerous parallel frequency bands recognizable within the second half of the call, representing a reflection of pulse rate (see Köhler et al. 2017 ). Calls from the same recording have been described by Lambert et al. (2017 ) using a different terminological scheme.