Bothriechis schlegelii (Berthold, 1846)

Arteaga, Alejandro, Pyron, R. Alexander, Batista, Abel, Vieira, Jose, Meneses Pelayo, Elson, Smith, Eric N., Barrio Amoros, Cesar L., Koch, Claudia, Agne, Stefanie, Valencia, Jorge H., Bustamante, Lucas & Harris, Kyle J., 2024, Systematic revision of the Eyelash Palm-Pitviper Bothriechis schlegelii (Serpentes, Viperidae), with the description of five new species and revalidation of three, Evolutionary Systematics 8 (1), pp. 15-64 : 15

Bothriechis schlegelii (Berthold, 1846)

Figs 6 , 12 , 13 , 14

Trigonocephalus schlegelii Berthold, 1846: 13. Holotype ZFMK 32554 (Fig. 6 ), a juvenile from Popayán, Colombia.

Thanatophis colgadora García, 1896: 27. Syntypes: lost, from "Cordillera Occidental de los Andes, en Calima, en Dapa, en San Antonio y en otros sitios de las montañas del Cauca".

Referred specimens.

All labeled Bothriechis schlegelii in Suppl. material 1.

Proposed standard English name.

Highland Eyelash-Pitviper, Schlegel’s Eyelash-Pitviper.

Spanish names.

Víbora de tierra fría, víbora de pestañas de Schlegel, guaruma.

Diagnosis.

Bothriechis schlegelii is diagnosed based on the following combination of characters: (1) two or three triangular and moderately raised supraciliary scales; (2) anterior dorsal head scales smooth; (3) gular scales much smaller than or similar in size to chinshields; (4) 3-11 interoculolabials; (5) 1-3 canthals which may be flat or slightly raised forming a ridge along the canthus; (6) loreal in contact with preocular in ~1/3 of specimens; (7) yellow morph absent; (8) dorsal bands black or dark brown; (9) no opposing kidney shaped dorsal marks; (10) black speckles on dorsal scales usually absent; (11) black speckling on ventral surfaces usually absent; (12) ventral surfaces never entirely white; (13) iris pale orange, light green, or golden yellow usually without speckles; (14) 21-25 dorsal scale rows at mid-body; (15) 139-156 ventrals in males, 135-153 in females; (16) maximum total length in males 834 mm, in females 969 mm.

Comparisons.

Bothriechis schlegelii sensu stricto is compared to other species of the genus previously subsumed under B. schlegelii sensu lato (differences summarized in Table 2 ). It differs from the other species except B. klebbai sp. nov. and B. khwargi sp. nov. in having two triangular and moderately raised supraciliary scales (supraciliaries either low and granular or enlarged and spinelike in the other species). Bothriechis schlegelii occurs near the distribution of B. torvus (Fig. 3 ), from which it differs by having anterior dorsal head scales smooth, 1-3 canthals (rather than 3-8), bands black or dark brown (rather than pink or red), ventral surfaces never entirely white, a lower number of ventrals in both males and females, and larger basal hooks on the hemipenial body (Fig. 14 ). Bothriechis schlegelii is most similar to B. klebbai sp. nov. and B. rasikusumorum sp. nov., but these other species occur parapatrically and are characterized by having small supraciliary scales, dorsal and ventral surfaces heavily speckled with black, gular scales similar in size or larger than chinshields, and no enlarged basal hooks on the hemipenial body. Bothriechis schlegelii differs from B. khwargi sp. nov. by having smooth anterior dorsal head scales (instead of keeled), a lower number of canthals, no reddish bands, and an entirely pale white belly.

Hemipenial morphology.

(n = 7; three depicted in Fig. 14 ) Everted and inflated, the organ is deeply bilobed, calyculate and noncapitate; hemipenial lobes uniformly cylindrical or tapering towards the tip; in sulcate and asulcate views, lobe crotch ornamented with densely packed spines that become larger distally; sulcus spermaticus centrolineal, bifurcate and with walls strongly defined (weakly in IAVH-R 5465 and ICN PR 13225), bifurcation occurs below bilobation point and proximal to the base of the hemipenial body; sulcus spermaticus branch runs to lobe tips; distal one third to one half of each hemipenal lobe densely ornamented with small calyces with strongly defined spinulate edges. In sulcate view, hemipenial body surface with small spinules medially, but with enlarged and strongly calcified lateral spines (basal hooks) followed by 2-4 rows of much smaller obliquely-arranged mesial spines that become gradually smaller towards each lobe’s capitulum; each hemipenial lobe ornamented with mesial and lateral spines about 1/3-1/10 the size of the large basal hooks; the spines in each lobe are replaced distally by calyces with strongly spinulate edges. In lateral view, hemipenial body and lobes with rows of spines, but otherwise non-spiculate; distal 1/3-1/2 of lobes strongly calyculate. In asulcate view, the center of hemipenial body is nude to barely spiculate; hemipenial lobes ornamented with 3 rows of smaller spines that decrease in size towards the lobe crotch.

Description of holotype.

A juvenile, SVL 183 mm, tail length 35.3 mm (19.3% SVL; tail-tip missing); head length 12.8 mm (7.0% SVL) from tip of snout to angle of jaw; head width 10.3 mm (80.5% head length) taken at broadest point; rostral broader than high (2.6 × 1.9 mm); nasal divided and not fused with first supralabial; loreal about 1/3 size of pit, in contact with preocular, postnasal, second canthal, 1 suprafoveal, 1 prefoveal, prelacunal, and supralacunal; prefoveals 3/4; subfoveals 2/2; postfoveals 0; prelacunal fused with second supralabial; sublacunals 2/2; supralacunal L-shaped and in contact with orbit; preoculars 1/1 (2/2 if supralacunal is considered a preocular); suboculars 1/1; postoculars 2/2; loreal pit large, directed anteriorly, located slightly below line drawn from center of eye to naris; supralabials 8/8 (including lacunolabial); infralabials 10/10, first pair meet posteriorly; mental broader than long (2.7 × 1.5 mm); 1 pair of chinshields; 3 pairs of gulars between chinshields and preventrals; preventrals 3; anterior internasals 3; canthals 2/2; 3/3 moderately triangular but low supraciliary scales; supraoculars oblong, 2.5 × longer than wide; intersupraoculars 5; anterior dorsal head scales smooth; posterior head scales keeled; interrictals 25; dorsal scale rows 21/21/17; ventrals 150; cloacal plate entire; 50 undivided subcaudals; tail prehensile.

Natural history.

Bothriechis schlegelii is an arboreal snake that inhabits evergreen montane forests, planted forests, coffee plantations, and urban/rural gardens. Based on our own field notes, iNaturalist records, and the literature ( Rojas-Morales 2012; Galofre-Ruiz 2016), vipers of this species are found at night perched on low (less than 3 m above the ground) shrubby vegetation or at ground level during the day, either in ambush posture or moving. Most observations are of snakes active on rocks, leaf-litter, grass, and even crossing roads during daylight hours. Santiago Ayerbe (pers. comm. to AA) reports that in Cauca, individuals of this species prey upon lizards (anolines and Pholidobolus ), rodents, and hummingbirds. Rojas-Morales (2012) reports that "though generally docile, individuals of B. schlegelii defend themselves with frontal displays and striking."

Venom.

Galofre-Ruiz (2016) reports two cases of human envenomation by this snake species in departments Caldas and Tolima. The victims developed pain at the site of the wound, paresthesia, and edema, but recovered with the use of polyvalent antivenom. Sevilla-Sánchez et al. (2021) report that most accidents caused by this snake involve coffee plantation workers bitten on the hands or face during the harvesting work. In a series of 1,653 cases of envenomation in Cauca province between 2009 and 2018, 8.4% were caused by B. schlegelii ( Sevilla-Sánchez et al. 2021), whereas 5.5% of 218 cases in departments Antioquia and Chocó between 1989 and 1990 were caused by a combination of B. schlegelii and B. torvus ( Otero et al. 1992a). Of these, one envenomation was moderate, 11 were mild, and none involved systemic complications. The venom in this Antioquian-Chocoan mixed Bothriechis sample was found to be the least edematous, hemorrhagic, and lethal (LD50 estimated as 10.3 mg/kg) among a sample of eight Colombian venomous snakes ( Otero et al. 1992b). Ayerbe et al. (1979) provided a report of a coffee plantation worker that died after being bitten on the tongue.

Distribution.

Bothriechis schlegelii is endemic to Colombia. It is known from at least 161 localities (listed in Suppl. material 3) on Colombia’s Cordillera Central and Occidental, from Cauca department in the south to Antioquia department in the north. The species occurs over an area of approximately 40,432 km2 and has been recorded at elevations 1,034-2,597 m above sea level (Fig. 3 ). Approximately 8.8% of the predicted area of distribution of B. schlegelii overlaps with that of B. torvus , but we did not find evidence of sympatry. In Valle del Cauca department, we found the two species separated by an airline distance of about 10 km.

Etymology.

The specific epithet schlegelii honors Hermann Schlegel (1804-1884), a renowned German ornithologist and herpetologist.

Conservation status.

We consider Bothriechis schlegelii to be included in the Near Threatened category following IUCN Red List criteria ( IUCN 2012) primarily because the species’ extent of occurrence is estimated to be much larger than the 20,000 km2 needed to meet B1 criteria for the Vulnerable category. However, although the species occurs in numerous protected areas (no less than 13; see Suppl. material 2), the majority of the species’ montane forest habitat has been destroyed. Based on the distribution model presented in Fig. 3 in combination with maps of vegetation cover of Colombia ( IDEAM 2014), we estimate that only ~23% of the species’ forest habitat is still standing.

Figures

Figure 3. Distribution of species of Bothriechis previously subsumed under B. schlegelii sensu lato. Each colored area is a geographic representation of the suitable environmental conditions for one of the clades recovered in the phylogeny of Fig. 2. Lime green shade in southeastern Panama represents overlap between between B. nigroadspersus and B. torvus.

Figure 6. Juvenile holotype of Bothriechis schlegelii ZFMK 32554 in lateral view. Photo by Alice Schumacher.

Figure 12. Photographs of some specimens of Bothriechis schlegelii from Antioquia department, Colombia, in life. a, c, f. From the live collection at INSV-SR, Serpentario Nacional de Colombia; b, d, e, g. from the live collection at SUA, Serpentario de la Universidad de Antioquia. Photos by Jose Vieira.

Figure 13. Photographs of some specimens of Bothriechis schlegelii in life. a. Adult from Planes de San Rafael, Risaralda department, Colombia; b-f. Adults from Popayan, Cauca department, Colombia, photographed at the Serpentario de la Universidad del Cauca. Photos by Jose Vieira and Amanda Quezada.

Figure 14. Hemipenial architecture of Bothriechis schlegelii in sulcate, lateral, and asulcate views. a. IAVH-R 6055 from Reserva Tesorito, Valle del Cauca department, Colombia; b. IAVH-R 6598 from Popayan, Cauca department, Colombia; c. IAVH-R 5465 from Fresno, Tolima department, Colombia. Photos by Duvan Zambrano.