Bioacoustics of Nasutixalus yingjiangensis

Distribution and natural history. Nasutixalus yingjiangensis is currently only known from its type locality in Yingjiang County, western Yunnan , China . The type locality is a small, isolated patch of mature montane evergreen forest with an average canopy height of 30 m ( Fig. 6 ); this forest remnant is surrounded by a mosaic of farmland, orchards, Betula alnoides timber plantation, and recently-cleared forest land. The male holotype SYS a005803 was found calling inside a small tree hole on a Tetradium glabrifolium tree at 21:30 h on 20 April 2017 (Fig, 6B); it has rained during the day. The tree hole was about 4.5 m above the ground; the opening was small and oval in shape (ca. 18 mm in width and 25 mm in length), and the tree hole cavity had conical shape and was about 100 mm in depth, 30 mm at the widest and 15 mm at its narrow end. The single female paratype SYS a005804 was found and collected from inside a large tree hole which was about ca. 5 m above ground during the day survey on 11 June 2017 ; the opening was about ca. 80 mm in diameter, while the tree hole cavity was about ca. 120 mm in depth. The other male paratype SYS a005803 was also found and collected from inside a small tree hole which was about ca. 2 m above ground during the day survey; the opening was about ca. 40 mm in diameter, while the tree hole cavity was about ca. 80 mm in depth. These observations suggest that the new species is a phytotelm-breeder, similar to N. jerdonii (Biju et al. 2016). We conducted four field surveys at the type locality between July 2016 and June 2017 . Many males were heard calling from the canopy (mostly ca. 4 m above ground) during summer surveys on 5 May 2016 , 20 April and 10 June 2017 ; no male calls were detected during the winter survey on 8 December 2016 . This indicates the new species breeds during the rainy season starting from mid-April. Calling activity was highest from dusk until midnight. Sympatric rhacophorid treefrogs recorded in the forest fragment during the surveys include Rhacophorus maximus Günther, Rhacophorus rhodopus Liu & Hu, Raorchestes longchuanensis (Yang & Li) , Kurixalus odontotarsus (Ye & Fei) and Polypedates cf. braueri (Vogt). No eggs and tadpoles of Nasutixalus yingjiangensis were found during the survey. Advertisement call. The call series contains a single, pulsed call of 0.297– 0.391 s duration (mean 0.344 ± 0.035 s , N=12). The intercall-interval is of 3.527– 6.150 s (mean 4.195 ± 0.770 s , N=11). Calls are repeated in series at a rate of 13.3 times per minute on average. All calls contain a fundamental frequency and a dominant frequency. The dominant frequency range is of 1.56–1.64 kHz, whereas the fundamental frequency is of 0.76 kHz. A third harmonic is weakly present at 2.32–2.41 kHz ( Fig. 7 ). To the human ear, the advertisement call of the new species is a short and low-pitched “uh”.