Bioacoustics of Uperoleia stridera

Description of holotype . Body size small, square and flattened in shape. Head is small, dorso-laterally compressed and shallow in depth (HD/SUL = 0.14, IO/HD = 1.24). When viewed laterally, snout is horizontal, tip is distinct and flattened; when viewed from above, the sides of the snout slope gradually up to a sharp angle that forms a flattened tip (EN/IN = 1.21). Canthus rostralis prominent, slightly protruding and well defined; loreal region slopes to jaw and is only slightly convex. Moderately rounded medial projection (synthesis of mentomeckelian bones) that matches notch on upper jaw. Nostrils directed upward and slightly outward; nares have no visible rim. Anterior corner of eye covered by slight flap of skin. Posterior edge of brow does not project over side of head side of head. Tympana covered by skin and parotoid glands. Tongue oval and elongate. Maxillary and vomerine teeth absent. EN larger than IN. Arms and hands gracile. Arms are of moderate length (ArmL/SUL = 0.43) and the fingers are moderately fringed and unwebbed. Finger length 3>4>2>1. Tubercles under fingers well developed; one on first and second, two on third and fourth. Well-developed outer palmar tubercle on distal portion of wrist; well developed inner palmer tubercle on medial portion of wrist. Nuptial pad of males on outer portion of first finger (beginning 2/3 from attachment of finger), extending to base of wrist and encroaching on inner palmar tubercle. Legs of moderate length (TL/SUL = 0.35, FTL/SUL = 1.74), thin. Toe length 4>3>5>2>1. Tubercles under toes well developed and conical; one on first and second, two on third and fifth, three on fourth. Toes moderately long, unwebbed, and strongly fringed. Small spade-shaped inner metatarsal tubercle, oriented along first toe. Outer metatarsal tubercle conical and highly reduced, oriented along fifth toe. Dorsum covered in fine tubercles which extend down arms, legs, and across the ventral surface. Cloacal flap present, moderately fimbriated. Parotoid gland round, extremely well developed and obvious, starting from just behind eye and extending posteriorly to arms and to below the angle of the jaw. Inguinal glands well developed, oblong, situated on the side of the body, extending from approximately halfway between arm and leg to the groin coloration; posterior half of gland covered when leg is normally situated. Coccygeal glands large, round and obvious; situated on the torso above the legs. No glands evident between inguinal and parotoid glands. Mandibular gland moderately developed, disrupted, and situated alongside the parotoid gland at the corner of the jaw. Coloration. In preservative ( Fig. 3 a), dorsum is a pale grey with large irregular dark patches. The parotoid and coccygeal glands are a light salmon pink. Ventrum is a dull yellow, and the outside edge of the chin is stippled with pigment. The anterior and posterior flash coloration patches are large and come in to close proximity on the dorsal surface of the thigh, separated by a thin strip of dark dorsal coloration. Variation In life, dorsal ground color frequently a light to rich medium brown, although individuals varied from reddish-orange to brownish-gray; some individuals displayed solid coloration, while in others the dorsal pigment was mottled with darker spots of a similar color. In mottled individuals, dorsum scattered with small to large irregular blotches of dark brown, especially near parotoid glands (forming a dark border around them) and coccygeal region; upper limbs also with dark brown markings, often forming bars on the legs. Some individuals displayed uniform coloration, while in others the dorsal pigment was mottled with darker spots of a similar colour. In most individuals the paratoid and coccygeal glands were slightly paler than the rest of the dorsal surface, sometimes suffused with orange. A slightly darker ‘V’ (pointing posteriorly) was present between the eyes of most individuals. Groin and femoral coloration, usually extending down to top of the crus, was always a bright red. All males had darkly pigmented chins, with the dark pigment extending just posterior to the arms. The venter of all individuals was a pale white with scattered darker flecks; ventral background pigment, except for a faint scattering of cream tubercles in some individuals, was not present on the thigh region. Advertisement call. Table 1 and Fig. 1 c summarize the main features of the call. This species produces a short sharp sound, audible as a grinding click. All individuals of U. stridera primarily gave calls consisting of two pulses ( Fig. 1 c), although some individuals also periodically produced three-pulse calls. The three-pulse calls had a similar pulse rate as the two-pulse calls, as can be noted by the small standard deviation in pulse rate in Table 1 . Individuals producing 3 pulse calls in our analyses were found both the far west (Up0248, Up0250 & Up0261) and east (Up1111) of the U. stridera distribution. Habitat. Usually encountered calling from flooded grasslands, streams, ponds, or roadside ditches.

Diagnosis. Distinguished from all other Uperoleia by a combination of small body size (males 19.0–25.0 mm) with flattened head (HD/SUL 0.14±0.01 [0.12–0.15]), broad snout (EN/IN 1.13±0.05 [1.05–1.21]), absence of maxillary teeth, finely tubercular skin, large red groin and femoral patches, large round parotoid glands reaching only to arms, well developed oval inguinal glands and large conspicuous coccygeal glands, toes and fingers unwebbed, and highly reduced inner and outer metatarsal tubercles. Further distinguished from U. trachyderma by lack of orange to red flecks on dorsum. A sharp click consisting of two to three pulses as an advertisement call repeated, on average, 90 times per minute at a faster rate than U. trachyderma ( Table 1 ).

Etymology. The name is a euphonious random combination of letters suggestive of the Latin word strido , meaning a creaking or grating sound. This refers to the grating nature of the call. Comparisons with other species. Uperoleia stridera can be distinguished from all species of Uperoleia except U. trachyderma by the combination of small size (SUL = 21.9 [1.7]), pronounced dorsolateral compression (HD/SUL = 0.14 [0.01]), extremely reduced metatarsal tubercles, and presence of fine dorsal tubercles. It is further distinguished from U. trachyderma by higher pulse rate ( Table 1 ; Fig. 1 c), two or three pulses per call ( vs. three or four), by location ( Fig. 2 d), and by the lack of scattered light orange to red tubercles on the dorsum.