Bioacoustics of Cophixalus nexipus

Description of holotype . An adult male with small right-lateral incision, vocal slits. Head moderately wide (HW/SV = 0.39), with oblique loreal region; canthus rounded, straight when viewed from above ( Fig. 7 A); nostrils directed laterally, closer to tip of snout than to eyes; internarial distance larger than distance from naris to eye (EN/ IN = 0.90, IN/SV = 0.093, EN/SV = 0.084); snout truncate when viewed from the side ( Fig. 7 B), shallowly angulate when viewed from above; eyes of moderate size (EY/SV = 0.12); eyelid approximately 2/3 width of interorbital distance; tympanum small (TY/SV = 0.026) and indistinct. Dorsal and lateral surfaces pustulose; ventral surfaces granulose; supratympanic fold small but distinct. Fingers with trace of basal webbing; relative lengths 3>4>2>1; first finger well developed ( Fig. 7 C). Third finger disc approximately twice width of penultimate phalanx (3rdF/SV = 0.077); that of first finger barely wider than penultimate phalanx. Subarticular and metacarpal tubercles low and poorly developed but distinct. Toes with basal webbing and fringes along T3 and T4 that extend to the disc, bearing discs with terminal grooves; relative lengths 4>3>5>2>1 ( Fig. 7 D). Toe discs smaller than those of fingers (3rdF/4thT = 1.30); disc of fourth toe less than 1.5 times width of penultimate phalanx (4thT/SV = 0.059); disc of first toe approximately same width as penultimate phalanx. Subarticular tubercles poorly developed; inner metatarsal tubercle low and elongate, outer lacking. Hind legs moderately long (TL/SV = 0.48). Dorsal ground color dark tan, irregularly mottled, smudged, and freckled with dark brown, this concentrated dorsolaterally, on snout, on posterior of head, and in a suprascapular chevron. A vaguely defined tan postocular stripe runs below the darker supratympanic fold. Rear of thighs tan mottled with dark brown; front of thighs same but with less dark mottling. Ventral surfaces straw yellow densely and evenly flecked with dark brown and with scattered gray-white punctations across abdomen. Iris black flecked with silver. Measurements (in mm). —SV = 22.7, TL = 11.0, HW = 8.8, HL = 7.4, IN = 2.1, EN = 1.9, SN = 3.0, EY = 2.7, TY = 0.6, 3rdF = 1.75, 4thT = 1.35. Variation. Mensural variation for the type series is shown in Table 5 . Adult males and juveniles appear to have slightly larger snouts than do adult females ( Table 5 ), but the difference is not great. Otherwise, no clear ontogenetic or sexually dimorphic differences are apparent in the type series. All specimens have clearly developed basal webbing between the toes, with that of the largest females appearing only slightly more conspicuous than what is seen in the other specimens. Character Males (n = 10) mean range Females (n = 4) mean range Immatures (n = 8) mean range SV (mm) 21.5 18.9–22.7 27.3 27.2–27.5 17.8 13.4–22.4 TL/SV 0.48 0.47–0.50 0.44 0.42–0.46 0.47 0.44–0.50 EN/SV* 0.086 0.081–0.090 0.080 0.077–0.081 0.088 0.081–0.097 IN/SV* 0.093 0.090–0.095 0.087 0.084–0.088 0.098 0.093–0.105 SN/SV 0.14 0.13–0.15 0.13 0.13–0.13 0.14 0.14–0.16 TY/SV 0.030 0.026–0.036 0.034 0.029–0.040 0.035 0.027–0.050 EY/SV 0.13 0.12–0.13 0.12 0.12–0.12 0.12 0.11–0.13 HW/SV 0.41 0.39–0.43 0.38 0.37–0.39 0.40 0.36–0.41 HL/SV 0.34 0.32–0.35 0.31 0.31–0.32 0.34 0.32–0.36 3rdF/SV 0.071 0.063–0.077 0.071 0.066–0.076 0.062 0.052–0.076 4thT/SV 0.056 0.053–0.059 0.056 0.053–0.064 0.051 0.044–0.058 EN/IN 0.92 0.86–1.00 0.92 0.88–0.96 0.90 0.86–0.95 3rdF/4thT 1.28 1.14–1.35 1.26 1.20–1.37 1.21 1.07–1.31 HL/HW 0.82 0.76–0.88 0.83 0.81–0.84 0.85 0.80–0.91 There is little color variation. Most specimens have the gray-brown appearance of the holotype , but three are lighter brown. Most have the dark suprascapular chevron, but this is often indistinct. The dark ventral flecking varies only slightly in intensity, with only four specimens having less contrast with the ground color than does the holotype . Color in life. From field notes for holotype BPBM 19323 ( Fig. 8 A): “Dorsum mud-brown, reddish middorsally, with gray suprascapular chevron and dark brown flecks all over. Iris mud-brown. Venter pale purple, except chin and throat, which are pale straw; entire venter speckled with dark brown flecks. Rear of thighs mudbrown with dark-brown mottling. One dark band across the forearm, another above the wrist.” BPBM 19321: “Dorsum green-gray with gray scapular mark and irregular gray or black flecking, with pustules, which are tan. Limbs tan with black flecking; rear of thighs same. Venter flecked light and dark gray with scattered white flecks on abdomen. Posterior belly and under legs light straw. Iris light brown.” BPBM 19320 was yellow-brown above; BPBM 19330 had a narrow, tan mid-dorsal stripe. Call. This species calls at night from the edges of streams. Most calling animals were perched on leaves 4–30 cm above ground, but one specimen was calling from under a rock. The call is a single, relatively long (0.99– 1.35 s), highly pulsed note lacking harmonic structure and frequency modulation ( Fig. 9 C) and delivered at intervals of 2.7 to 50 s apart ( Table 6 ). To the human ear the call sounds similar to a squeaky door hinge or a throaty snore. The number of pulses/call varied from 44–63, and pulse rate varied from 41.5–57.4/s. Notes increase in amplitude relatively rapidly and maintain approximately maximum amplitude for most of the note before decreasing again relatively rapidly ( Fig. 9 A). Notes have lesser-amplitude pulses at the beginning and end of the note, giving the waveform a rounded rectanglar shape, with most notes showing approximately equal-amplitude pulses for most of their duration ( Fig. 10 A), but for the holotype notes frequently increase to peak amplitude more gradually than they decrease, giving the amplitude envelope a slight skew to the left ( Fig. 10 B). Pulsing is invariably slower at the beginning, and quicker at the end, of each note. Dominant frequency varies from 2.80–3.96 kHz ( Table 6 , Fig. 9 B).