Bioacoustics of Rhombophryne botabota

Diagnosis. Within the genus Rhombophryne , R. botabota can easily be distinguished from R. testudo , R. coudreaui , R. matavy , and R. maraorao sp. nov . by smooth skin (vs rough), absence of chin barbels (vs general presence), longer hindlimbs ( HIL / SVL 1.41–1.75 vs 1.10–1.41); from R. mangabensis by larger body size ( SVL 24.2–32.2 mm vs 19.6–23.2 mm ), and smooth skin (vs finely granular with scattered warts); from R. savaka by larger body size ( SVL 24.2–32.2 mm vs 18.8–20.9 mm ), absence of a diastema in the vomerine teeth (vs presence), and absence of inguinal spots (vs occasional presence); from R. mavokely sp. nov . , R. ornata , and members of the R. ellae species group by the absence of reddish orange colouration on the posterior thigh and in the inguinal region (vs presence); from members of the R. minuta species group by generally shorter hindlimb length ( HIL / SVL 1.41–1.75 vs 1.73–1.84), and less gracile habitus; from R. proportionalis by much larger adult body size ( SVL 24.2–32.2 mm vs 11.0– 12.3 mm ); and from all members of the R. serratopalpebrosa species group by the absence of superciliary spines (vs presence). Within the R. laevipes species group, see the account of R. laevipes above for distinction from that species. Rhombophryne botabota can be distinguished from R. nilevina by smaller body size ( SVL 24.2–32.2 mm vs 41.2–57.2 mm ), absence of white spots in the inguinal region and on the posterior thigh and ventral shank (vs sometimes present), and tonal (vs pulsed) advertisement call that is shorter (call duration 161–201 ms vs 538–598 ms) and higher in dominant frequency (1256–1291 Hz vs 526–534 Hz). For distinction from newly described members of this species group, see their respective descriptions below.

Natural history. Rhombophryne botabota is a semi-fossorial or detriticolous species found in mid-elevation humid forest. In the vicinity of ‘ Camp Simpona’ in November 2016 , we found R. botabota to be moderately abundant during surveys. Specimens were routinely found by raking over quadrats of leaf litter, or collecting the quadrats in rice bags and sorting through them by hand. Previously, most specimens had been collected using pitfall traps ( Scherz et al. 2016 a ). Some calls were heard, but no individuals could be observed calling. Paratype ZSM 538/2009 was recorded by Scherz et al. (2016 a ) to have a subulinid snail in its gut, making it the only record of gastropod consumption by a Rhombophryne species.

Call. The allocation of the analysed recording to R. botabota is slightly tentative, as the recorded individual was not seen calling. However, R. botabota was the only Rhombophryne species found at the place of call emission (see Scherz et al. 2016 a ). The advertisement call recorded on 24 June 2009 (12: 00 h) at Angozongahy site, Makira (estimated air temperature 22–24 ° C), consists of a single tonal note of moderate duration repeated at regular intervals, but apparently not arranged in regular call series. Calls lack any frequency modulation, but exhibit moderate amplitude modulation, with call energy increasing from the beginning of the call and reaching its maximum at approximately half of the call’s duration (Fig. 38 ). Numerical parameters of 4 analysed calls are as follows: call duration (= note duration) 161–201 ms (180 ± 19 ms); inter-call intervals 2529–2716 ms (2638 ± 97 ms); dominant frequency 1256–1291 Hz (1274 ± 16 Hz); prevalent bandwidth 1100–3200 Hz; harmonic frequency bands recognizable at about 630, 1910, 2580 and 3160 Hz. Calls from the same recording have been described by Scherz et al. (2016 a ) using a slightly different terminological scheme. Slight differences in temporal measurements when compared to Scherz et al. (2016 a ) result from different recognition of the ‘ tapering tail’ in calls, which we here consider to likely represent an echo effect.

Definition. Within the R. laevipes group, this species appears to be sister to a clade consisting of 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) medium body size, adult SVL 24.2–32.2 mm ; (2) head wider than long ( HW / HL 1.44–1.69); (3) moderately small eyes ( ED / HL 0.33–0.38); (4) moderately long hindlimbs ( HIL / SVL 1.41–1.75); (5) small inner metatarsal tubercle ( IMTL / FOL 0.08–0.13); (6) outer metatarsal tubercle absent; (7) second finger shorter than or equal in length to fourth; (8) third toe distinctly longer than fifth; (9) dorsal skin smooth; (10) absence of chin barbels; (11) absence of pronounced superciliary spines; (12) absence of distinct inguinal spots (sometimes dark brown lines converging anterodorsally); (13) absence of distinctive markings along the posterior thigh; (14) unfortified skull without expansion of maxilla or posterior process of angulosplenial; (15) clavicles present, thin, curving; and (16) advertisement call (based on 4 analysed calls by one individual) tonal, with (17) call duration 161–201 ms, (18) inter-call interval 2529–2716 ms, and (19) dominant frequency 1256–1291 Hz. Rhombophryne botabota 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 304, ‘ T’ at site 568, and ‘ A’ at site 682. No diagnostic sites were identified for 16 S 3 ’.