Hypsiboas sibleszi (Rivero)

Myers, C. W. & Donnelly, M. A., 2008, The Summit Herpetofauna Of Auyantepui, Venezuela: Report From The Robert G. Goelet American Museum-Terramar Expedition, Bulletin of the American Museum of Natural History 2008 (308), pp. 1-147 : 58-60

Hypsiboas sibleszi (Rivero) Figures 35–36

Hyla sibleszi Rivero , ‘‘1971’’ [1972]: 182–183, [pl. 1], figs. A–B (narrowband sound spectrogram and photo of preserved holotype). Holotype: Univ. Puerto Rico at Mayagüez 31778, from Paso del Danto, La Escalera, entre El Dorado y Sta. Elena de Uairén , 1300–1400 m, Serranía de Lema , Edo. Bolívar, Venezuela, collected March 22, 1968, by J. A. Rivero and J. Pulido.

Hyla sibleszi: Hoogmoed, 1979a: 23–33 (extensive redescription and diagnosis), figs. 7 (hand and foot), 8 (tadpole), pls. 3a (preserved spec.), 5 (sound spectrogram). Duellman, 1997: 19–20, fig. 11[B] (color photo of female).

Hypsiboas sibleszi (Rivero) , Faivovich et al., 2005: 88, 162.

MATERIAL: Camp 4, 1600 m: AMNH A- 164849–164851. All from the 1994 AMNH – TERRAMAR Expedition to Auyantepui.

These frogs were found only at Camp 4, where conditions were much wetter than at the other camps. Five adult males were collected. These males are 30.6–33.1 mm SVL (x¯ 5 31.46 mm, S.D. 5 1.02 mm, N 5 5); tibia length 53 % –54 % of SVL; head width 39 % –41 % of SVL, 84 % –91 % of diagonal head length; eye length slightly shorter than distance from its anterior edge to center of naris ( EN /eye 5 1.06–1.13); upper eyelid less than half the width of interorbital space ( IOD /eyelid 5 2.00–2.50); disc on finger III wider than discs on toes III – IV, which are subequal.

COLORATION: In life (fig. 35), the ground color of the five adult males varied either from light green to yellowish green, or from pale to medium blue-green.15 A variable number of small pale yellow dots sparsely scattered on dorsum, conspicuous or not; some specimens with dorsal surfaces also densely dotted with brown melanophores overall, this dotting inconspicuous or not evident in others (but conspicuously present in all specimens in preservative). Digits distally light orange above and below. Pale interorbital bars and dorsolateral stripes are lacking in this sample.

Vocal sac light yellow-green; rest of ventral surfaces light blue-green. Venter somewhat transparent, with heart, liver (including gall bladder), and intestinal tract tightly bound in white peritoneum; linea masculina visible.

15 Hoogmoed (1979a: 26) suggested that dorsal ground color was sexually dimorphic in Hyla sibleszi , with females dark bluish green and males light green. However, both colorations apply to our sample of adult males, and Duellman (1997: 11) published a photograph of a light green female.

Bones green. Iris pale bright yellow, with suffusion of light red-brown around pupil and with fine black venation.

NATURAL HISTORY AND VOCALIZATION

Specimens of Hypsiboas sibleszi were found on the night of February 23, calling on vegetation from a few cm to about 2 m above a stream at Camp 4. The recorded advertisement call is a single note of 0.06 sec duration, with a fundamental frequency at about 1125 Hz and with emphasized frequency in the range of 1750–2080 Hz. Internote interval is variable; seven calls of what seem to be the same individual are spaced 9.2–23.6 sec apart on a recording made at 18.8 ° C. ( Hoogmoed [1979a: 29] reported more frequent calling at 10–11 notes per minute.)

The waveform and wideband spectrogram of H. sibleszi show the note to be strongly pulsatile albeit somewhat loosely organized, his sound spectrogram is uninformative, showing an overloaded note (probably narrowband) on a mislabeled time axis. Rivero (‘‘1971’’ [1972]: 189, fig. A) showed two notes, about 1.7 sec apart, graphed with a narrowband filter.

with the initial two pulses well separated from the others (fig. 36). Another waveform and wideband spectrogram from an unstated locality in Bolívar state shows at least one initial pulse to be well separated (Señaris and Ayarzagüena, 2006: fig. 6).

The notes have a quacklike sound on our February recording from the Auyán summit, which seems consistent with Duellman’s (1997: 19) ‘‘wrack’’ for frogs calling in January in the La Escalera Region about 110 km E of Auyantepui (region of the type locality of H. sibleszi ). However, Duellman contrasted that sound with ‘‘one or two soft Phyllomedusa -like clucks’’ given by frogs calling during the month of July, which suggests the possible existence of temporal complexity in vocalization. In another report from the La Escalera region, Hoogmoed (1979a: 39, pl. 5C) quite differently described the call as a short low-pitched ‘‘wraah’’, but

REMARKS

Hypsiboas sibleszi is best known from Hoogmoed’s (1979a) detailed redescription and analysis of distribution. It is an upland species appearing to have a moderately widespread distribution from Guyana (Mac- Culloch and Lathrop, 2005: 27, color fig. 2F) west into Bolívar, Venezuela, although the range is probably disjunct. It was thought to be one of the few amphibians and reptiles shared between Auyantepui and the neighboring Chimantá (Myers, 1997), but the Chimantá specimens prove to be a different species that is close to H. jimenezi (fn. 14; Señaris and Ayarzagüena, 2006: 316).

The westernmost-known station for Hypsiboas sibleszi is some 400 km W of Auyantepui , at Cerro Guanay, where the frogs are relatively large (see map in Señaris and Ayarzagüena, 2006: fig. 5). Gorzula and Señaris (1999: 36) mentioned four males collected by Gorzula that measured 39–42 mm SVL (x¯ 5 40.3 mm). Our sample of 20 adult males from Cerro Guanay are in the range of 34.0–39.0 mm SVL (x¯ 5 35.75 mm, SD 1.480 mm) ; the one adult female in our sample is 41.2 mm SVL. Even allowing for individual measuring error, there may be a size difference between the demes sampled by Gorzula and by us on Cerro Guanay. Some of the Guanay frogs have a pale interorbital bar and dorsolateral stripes but were otherwise similar in living color to our sample from Auyantepui . However, differences in vocalization (e.g., in note duration and pulse structure) may necessitate specific status for the sibleszi -like frogs on Cerro Guanay (unpublished data) .