Bioacoustics of Microhyla sundaica

Natural history notes. The new species is often recorded while calling from the banks or in shallow rain puddles or swamps (Fig. 15 A – B ). Although most of the M. sundaica sp. nov. records came from recreational forest areas, this species is also likely to inhabit pristine forests, being especially abundant along the streams or near shallow intermittent pools. Inger et al. (2017) reported that in Borneo male individuals of this species (which he referred to as M. berdmorei ) were encountered during vocalization activity while they were hiding in burrows or under dead leaves in the leaf litter; usually males call from ca. 1–5 meters from waterpools or stream banks. In Borneo, this species prefers stagnant temporary waterbodies for reproduction ( Inger et al. 2017 ). Microhyla sundaica sp. nov. has mostly crepuscular activity and is often observed at night actively foraging after heavy rains, usually from 19: 00 to 23: 00 h. The diet and predators of the new species remain unknown. At the type locality in environs of Sungai Tua Recreational Forest, Selangor State , Malaysia (Fig. 15 A ), M. sundaica sp. nov. was recorded in sympatry with Ingerophrynus parvus (Boulenger, 1887) , Kalophrynus kiewi Matsui, Eto, Belabut & Nishikawa, 2017 and M. butleri Boulenger, 1900 . Inger et al. (2017) noted that the new species occurs in mature and secondary forests, mostly at low elevations. Sumarli et al. (2015) reported that male specimens of this species were recorded at night while calling from the top of a boulder at the water’s edge within small puddles; while some specimens were found sitting on mud or in flooded ruts, most were hiding in vegetation along the forest trails. In Peninsular Malaysia , the new species was recorded in sympatry with M. heymonsi Vogt, 1911 , and with M. butleri ( Sumarli et al. 2015 ) . Dring (1979) reported that in Borneo, M. sundaica sp. nov. males were calling in one chorus with M. borneensis Parker, 1928 . In Selangor and Kedah State , Peninsular Malaysia , the species prefers temporary, stagnant pools of water for breeding, with rich leaf litter around ( Leong 2004 ; our observations); males usually call from small holes in the ground on the bank ca. 15–25 cm from the wateredge, or while floating on the water surface (Fig. 15 C – D ).

Advertisement call. We recorded the advertisement call of the new species in Gunung Jerai Mt ., Kedah , Peninsular Malaysia . The male advertisement call of M. sundaica sp. nov. consists of a series of short nasal rasping squeaks. Each call series consisted of usually seven calls (6–8) emitted at a 1.8 ± 0.3 s (1.34– 2.30 s ) interval; a single call series lasted for 3.8 ± 2.3 s (2.5–6.7). Individual calls lasted for 0.16 ± 0.03 s (0.12–0.21), and each call consisted of 13 ± 2.3 (8–16) pulses. Each call consisted of two syllables: the introductory note and the main call; the frequency of the introductory note was much lower (739 ± 112 Hz) than that of the main call; the relative amplitude sharply increased in the middle of the call, reaching its maximum in the second half of its duration, and then slowly decreased towards the call end (Fig. 10 C ). The call’s peak frequency was 2029 ± 106 Hz (1898–2203 Hz).