Bioacoustics of Mantidactylus grubenmanni

Natural history .—As reported by Glaw and Vences (1999) , males in An’Ala have been observed calling at daytime in a shallow, partly sun-exposed swamp with dense vegetation in primary forest, near or on perches directly above the water. They were sitting on leaves, fallen branches and similar structures, generally only 0–2 cm above the water level. Calling behaviour of one individual male was observed for several minutes. This specimen moved forward during its vocalisations, in a conspicuously jerky, disrupted way. In the Ranomafana area, found along streams in rainforest inside Ranomafana National Park and forest fragments in Ambolo and Ampitavanana, but not found outside forest. Specimens were observed sitting in areas of shallow water and along the banks or hiding in leaf litter in the vicinity of a stream. At Ranomafana and surrounds found at an elevational range between 641–1052 m a.s.l. A female with visible eggs was found in June 2010 at Ampitavanana, another in March 2011 at Ambolo. ZMB 81960 (JCR 694) was observed calling at a stream bank at Imaloka inside Ranomafana National Park at late afternoon (17:00 h) on 14 March 2011 .

Calls .—The advertisement call of M. grubenmanni , recorded on 3 February 1996 at An’Ala, 29.6°C air temperature ( Vences et al. 2006 : CD2, track 71), consisted of a very short, pulsed note, emitted singly or in long regular series at very fast succession ( Fig. 60 ). Amplitude modulation was present, with relative amplitude increasing from the beginning of the call, reaching its maximum with the terminal pulse. Pulse structure within notes was somewhat complex, with terminal pulses having longer duration and being more narrowly spaced. Numerical parameters of 52 analysed calls were as follows: call duration (= note duration) 26–87 ms (68.1 ± 17.5 ms); 3–7 pulses per note (5.5 ± 0.9); pulse duration 2–12 ms (4.5 ± 2.8); pulse repetition rate within notes 47.6–181.8 pulses/s (89.2 ± 40.3); dominant frequency 2015–2338 Hz (2286 ± 104 Hz); prevalent bandwidth 1500–3400 Hz; call repetition rate (= note repetition rate) within regular series ca 310 calls/min. The longest call series recorded had a duration of 8.52 s and contained 43 calls. Calls recorded on 14 March 2011 at Ranomafana from specimen ZMB 81960 (JCR 694) agree in structure and parameters with those described above from An’Ala. The longest regular call series from this recording had a duration of 7.15 seconds and contained 33 calls, repeated at a rate of 272 calls/minute. Tadpoles.— The tadpole of this species has not been described.

Diagnosis .— Mantidactylus grubenmanni sp. nov. is a member of the M. tricinctus clade as revealed by the phylogenomic analysis, and sister to M. tricinctus . See Table 4 for a list of diagnostic morphological characters. The combination of very small body size (below 20 mm male SVL), connected lateral metatarsalia, reduced webbing, presence of a light (often yellowish) marking on snout tip, a yellow inguinal marking, and a short, pulsed advertisement call emitted in rapid succession in regular series, readily distinguishes M. grubenmanni sp. nov. from all other nominal species of Brygoomantis except its sister species M. tricinctus from which it is morphologically indistinguishable. It differs from M. tricinctus by fewer pulses per note in advertisement calls, and a generally lower pulse repetition rate. For detailed distinction from other new species described herein, see the respective species accounts. A full list of molecular diagnostic sites in the 16S gene of M. grubenmanni sp. nov. in pairwise comparisons to all other Brygoomantis species is provided as Supplementary appendix.