Bioacoustics of Mantidactylus bellyi

Diagnosis .—A member of the M. ulcerosus clade as revealed by the phylogenomic analysis, and sister to the morphologically very similar M. ulcerosus . See Table 4 for a list of diagnostic morphological characters. The combination of a large body size of up to 46 mm , strongly tubercular dorsal skin in most individuals, absence of dorsolateral ridges, large tympanum size in males (10– 17% of SVL) and absence of white spots on flanks and of white marking on snout tip distinguishes M. bellyi from species of the other clades. Some species in the M. fergusoni clade can be morphologically similar, but they occur in eastern Madagascar (vs Sambirano and North West regions), and have strongly different advertisement calls ( Table 4 ). Within the M. ulcerosus clade, the species differs by its large body size and tubercular dorsal skin from M. schulzi , and by its advertisement call consisting of single calls (vs note series) from M. schulzi and M. ulcerosus . For detailed distinction from new species described herein, see the respective species accounts. A full list of molecular diagnostic sites in the 16S gene of M. bellyi in pairwise comparisons to all other Brygoomantis species is provided as Supplementary appendix.

Natural history .—Similar to M. ulcerosus , M. bellyi is found in and along small shallow streams in primary as well as degraded rainforest and dry forest. Males were heard calling at night from the water or at the edge of the water. Rasolonjatovo et al. (2018) report on the attempted predation of a Boophis tadpole by an adult M. bellyi and reported an adult female M. bellyi repeatedly emitting a series of rapid scratch-like vocalisations from a hidden place on the rough magmatic rock forming the edge of the pool. Rasolonjatovo et al. (2020) report on thermal ecology of M. bellyi on Montagne d’Ambre across its elevational range ( 467–1394 m a.s.l.), and Rasolonjatovo et al. (2022) described its genetic diversity and phylogeographic structure on Montagne d’Ambre.

Calls.— The advertisement call of M. bellyi , recorded on 17 March 2000 at the entrance of Montagne d’Ambre National Park, 21.6°C air temperature ( Vences et al. 2006 : CD 2, track 75), consists of a regularly pulsed note ( Fig. 28 ), emitted at irregular intervals, but not regular call series. Notes exhibited distinct amplitude modulation, with call energy being highest at the beginning of the note, followed by continuous decrease of energy towards the note’s end. Pulses were very narrowly spaced. Numerical parameters of three analysed calls were as follows: call duration (= note duration) 594–682 ms (630.0 ± 46.1 ms); 41–46 pulses per note (43.7 ± 2.5); pulse duration 7–11 ms (8.3 ± 1.2 ms); pulse repetition rate within notes 63.8– 77.8 pulses/s (69.9 ± 4.9); dominant frequency 2497–2583 Hz (2532 ± 32 Hz), with a second peak of almost identical energy at around 880–920 Hz; prevalent bandwidth 660– 3200 Hz; call repetition rate (= note repetition rate) not identifiable with available recordings. Variation in the advertisement call over populations of M. bellyi on Montagne d’Ambre was investigated by Rasolonjatovo et al. (2022) for 23 male specimens. In all cases, the calls typically consisted of a single note, with minor variation of call duration between individuals, and without significant differences in call parameters between sites. Dominant frequency was negatively correlated with body size. Tadpoles. —The tadpole of this species has not been described.