Hyperolius chlorosteus

Gongomin, Basseu Aude-Inès, Kouamé, N’Goran Germain, Agoh, Konan Laurent, Kanga, Kouassi Philippe & Rödel, Mark-Oliver, 2022, New biological data for two rare reedfrog species, Hyperolius nimbae Laurent, 1958, and H. chlorosteus (Boulenger, 1915) (Anura: Hyperoliidae), Amphibian & Reptile Conservation (e 318) 16 (2), pp. 88-103 : 93-96

Observations on H. chlorosteus

Habitat, population size, and activity of H. chlorosteus . Specimens of H. chlorosteus were found in MNINR in a patch of dense, broadleaf and evergreen primary forest at a mid-elevation along a torrent stream (07°34.652’N, 008°24.966’W; 716 m asl; Fig. 7A ), as well as in a degraded forest edging a large stream at Yéalé village (07°31.932’N, 008°25.508’W; 387 m asl; Fig. 7B ). From April–November, the rainy season, a total of 341 H. chlorosteus were captured in the two sites, always at night along the streams ( Fig. 8 ; Appendix 2). In the dry season, from December to March, no signs of the species’ presence were observed. Males started calling at around 1800 h GMT, most often after heavy rainfall. In a patch of primary forest, 327 calling males perched on leaves and branches of small shrubs at ~1.5–2.0 m height above the ground (e.g., Fig. 7C ) were captured. The other recorded males were heard calling from very high up in tall trees along the forest stream. A few calling males (N = 11) were also found in a degraded forest, edging a large stream at Yéalé village (07°31.932’N, 008°25.508’W; 387 m asl; Fig. 7B ). There, they called on shrubs, with the calling sites ranging from 1.80 m above the ground to much higher. Sympatric frogs were Leptopelis macrotis , Hyperolius picturatus , and White-lipped Frogs Amnirana sp. “albolabris west.”

Morphology of H. chlorosteus . The snout-urostyle lengths of 15 males, retained as vouchers, ranged from 31.5–35.0 mm (33.8 ± 1.3 mm), thus occurring within the known range of H. chlorosteus ( Schiøtz 1967) . The head was slightly longer (12.0 ± 0.1 mm; range: 12.0– 12.2 mm) than broad (11.5 ± 0.7 mm; range: 10.5–13.0 mm); the interorbital space ranged from 5.9–7.2 mm (6.5 ± 0.4 mm); the distance between eye and nostril (3.0 ± 0.2 mm; range: 2.5–3.5 mm) was approximately twice the distance from nostril to tip of snout (1.4 ± 0.6; range: 0.6–2.4 mm); the eye diamter (5.1 ± 0.3 mm; range: 4.4–5.5 mm) was larger than internarial space (2.6 ± 0.4 mm; range: 2.1–3.0 mm) and tympanum diameter (2.8 ± 0.2 mm; range: 2.2–3.0 mm); the crus length (17.0 ± 0.7 mm; range: 15.4–18.1 mm) slightly exceeded the thigh length (15.9 ± 0.8 mm; range: 14.9–16.9 mm); and foot length including the longest toe ranged from 21.5–23.5 mm (22.2 ± 0.8 mm).

Two females measured 36.8 and 37.5 mm in SUL. As in the males, their heads were slightly longer (13.5 mm) than broad (13.2 mm); interorbital spaces were 7.0 and 7.2 mm; the distance between eye and nostril was longer (3.3 ± 0.3 mm; range: 3.1–3.5 mm) than the distance from nostril to tip of snout (1.9 ± 0.1 mm; range: 1.9–2.0 mm); the eye diamter (5.0 ± 0.1 mm; range: 5.0– 5.1 mm) exceeded the internarial space (2.9 ± 0.1 mm; range: 2.9–3.0 mm) and tympanum diameter (2.9 ± 0.1 mm; range: 2.8–3.0 mm); the crus length (17.7 ± 0.3 mm; range: 17.5–17.9 mm) slightly exceeded thigh length (16.9 ± 1.5 mm; range: 15.9–18.0 mm); and foot length including the tarsus and longest toe ranged from 23.5–23.8 mm (23.6 ± 0.2 mm) .

The color pattern of H. chlorosteus showed some variations (see Figs. 7 and 9 ), however, all were within the range known for the species (compare Schiøtz 1967; Rödel 2003; Channing and Rödel 2019).

Reproduction of H. chlorosteus . One female perched on a broad leaf of a shrub overhanging a forest stream, at ~ 1.5 m height, was captured. Eggs were visible through its ventral skin ( Figs. 7D and 9F ). An amplectant couple was seen sitting on low vegetation in this site ( Fig. 7E ). This couple was placed in a terrarium and a clutch of 62 eggs was present the next morning. The eggs were attached to the glass above the water. They had beige and dark poles surrounded by a thin transparent capsule ( Fig. 7F ). Egg diameters varied from 2.0‒ 2.5 mm, mean 2.2 mm (SD: ± 0.25 mm). The jelly of H. chlorosteus eggs is slightly opaque. Six additional H. chlorosteus clutches observed in Taï National Park, south-west of Ivory Coast, ranged from 54‒ 122 eggs (86.2 ± 28.8 eggs; Table 2).

Vocalization of H. chlorosteus . Five advertisement calls were recorded from one male ( Fig. 10 ). The calls were repeated 2–7 times ( Fig. 10B ). The acoustic impression of the call is a low-pitched, far ranging metallic click with a mean duration of 0.87 ± 0.34 s (range: 0.51– 1.41 s). The duration intervals between calls averaged 2.90 ± 1.27 s (range: 1.36– 4.0 s, N = 4). The mean fundamental frequency was 1,303.12 ± 83.85 Hz (range: 1,265.62– 1,453.12 Hz, N = 5), while the dominant frequency reached 2,606.3 ± 167.70 Hz (range: 2,531.25–2,906.25 Hz, N = 5). The maximum frequency intensity was at 2,643.75 ± 167.70 Hz (range: 2,531.25–2,906.25 Hz, N = 5), and the minimum frequency intensity averaged at 2,531.25 ± 229.64 Hz (range: 2,343.75–2,906.25 Hz, N = 5).

Threats to H. chlorosteus . Major threats to H.

chlorosteus were observed at Yéalé, where some forest pockets along streams had been cleared and converted to cocoa and coffee plantations, as well as rice cultivation.

Figures

Fig. 7. (A–B) Typical forest streams in the Mount Nimba Integrated Nature Reserve where Hyperolius chlorosteus breeds.A calling male (C), a female (D), a couple in amplexus (E), and their clutch (F) which was deposited on a leaf above a forest stream.

Fig. 8. Number of Hyperolius chlorosteus captured from 2 August 2019 to 8 July 2020 along lowland forest streams at Mount Nimba.

Fig. 9. Variation of color pattern of Hyperolius chlorosteus from Mount Nimba Integrated Nature Reserve, western Ivory Coast.

Fig. 10. Calling male of Hyperolius chlorosteus(A) with(B) waveform (above), spectogram (centre)and powerspectrogram (below), of the species’ advertisement call, from Mount Nimba Integrated Nature Reserve. Note that the data for five calls are shown.