Bioacoustics of Mantidactylus inaudax

Calls .—The advertisement call of M. inaudax , recorded on 23 June 2009 , at Makira West, at an estimated air temperature of 20–25°C, consisted of a pulsed note, emitted isolated or in short series containing 5–7 calls ( Fig. 75 ). Notes exhibit amplitude modulation, with call energy rapidly increasing from the beginning of the note, reaching its maximum after approximately one third of the note’s duration. Pulse repetition rate within notes was highest at the beginning and decreases towards the note’s end. Numerical parameters of 14 analysed calls were as follows: call duration (= note duration) 196–367 ms (268.6 ± 66.4 ms); 19–28 pulses per note (22.6 ± 3.9); pulse duration 3–6 ms (4.3 ± 0.9 ms); pulse repetition rate within notes 55.6–130.4 pulses/s (85.8 ± 23.9); dominant frequency 1146–1276 Hz (1200 ± 41 Hz); prevalent bandwidth 800–3400 Hz; call repetition rate (= note repetition rate) within series ca 75 calls/min. Calls recorded on 25 March 2006 at the crossing of the Moramanga-Anosibe An’Ala and Besariaka roads, at an estimated air temperature of 20–25°C, were emitted in regular series and agreed perfectly in character with the calls described from Makira West above and differd only slightly in numerical parameters (n = 9): call duration (= note duration) 199–312 ms (254.9 ± 35.9 ms); 17–23 pulses per note (20.3 ± 2.2); pulse duration 3–7 ms (4.7 ± 1.1 ms); pulse repetition rate within notes 61.2–142.9 pulses/s (87.1 ± 28.9); dominant frequency 738–961 Hz (814 ± 72 Hz); prevalent bandwidth 500–3500 Hz; call repetition rate (= note repetition rate) within series ca 60–90 calls/min. The most significant difference was the lower dominant frequency which was possibly due to a larger SVL of the calling male. Tadpoles.— The tadpole of M. inaudax was described under the name ‘ M. biporus ’ by Knoll et al. (2007) .

Diagnosis .— Mantidactylus inaudax belongs to the M. inaudax clade according to our phylogenomic analysis.See Table4 for a list of diagnostic morphological characters. The combination of small to moderate body size (male SVL 22–30 mm , female SVL 27–33 mm ), rather smooth dorsal skin without dorsolateral ridges, large tympanum size in males (12–16% of SVL), presence of white spots on flanks in at least some individuals, and absence of a white marking on the snout tip, distinguishes M. inaudax from species of the M. betsileanus , M. curtus , M. fergusoni , M. tricinctus , and M. ulcerosus clades. M. stelliger ( M. stelliger clade) differs by smaller body size and less developed foot webbing. Species of the M. biporus clade differ as follows: M. biporus by smaller tympanum in males, and a higher pulse repetition rate in advertisement calls; M. augustini by longer hindlimbs, fewer pulses per note, and lower pulse repetition rate in advertisement calls; M. bletzae by a somewhat smaller body size, presence of dorsolateral ridges, longer hindlimbs, and more developed foot webbing; M. brevirostris by less developed foot webbing, possibly smaller body size, and differences in colour pattern; M. eulenbergeri by smaller body size; M. glosi by smaller body size, more granular dorsal skin and shorter hindlimbs ( Table 4 ). For a distinction from new species and subspecies in the M. inaudax clade, see the diagnoses in the respective taxa accounts below. A full list of molecular diagnostic sites in the 16S gene of M. inaudax in pairwise comparisons to all other Brygoomantis species is provided as Supplementary appendix.