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Higher TaxaColubridae (Dipsadinae), Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
Common NamesE: Bev Ridgely’s Snail-Eater
S: Caracolera de Bev Ridgely 
DistributionEcuador (Azuay, Chimborazo, El Oro, Guayas, Los Ríos and Manabí), NW Peru (Piura), elevation 5 - 1206 m

Type locality: Reserva Buenaventura, province of El Oro, Ecuador (S3.65467, W79.76794; 524 m  
TypesHolotype: MZUTI 5416 (Figs 6, 7), adult male collected by Matthijs Hollanders on August 01, 2017). Paratypes. AMNH 22092, adult male collected by George H. Tate on December 01, 1921 at Bucay, province of Guayas, Ecuador (S2.19788, W79.12909; 433 m). CORBIDI 3791, adult male collected by Pablo Venegas and Caroll Landauro on May 07, 2009 at El Caucho, department of Tumbes, Peru (S3.81438, W80.27101; 379 m). CORBIDI 3792, adult female collected by Pablo Venegas and Caroll Landauro on May 07, 2009 at El Caucho, department of Tumbes, Peru (S3.81438, W80.27101, 379 m). CORBIDI 7894, adult female collected by Vilma Durán and Germán Chávez on October 21, 2010 at El Caucho, department of Tumbes, Peru (S3.81844, W80.26856; 478 m). CORBIDI 7994, adult female collected by Pablo Venegas on September 24, 2010 at El Caucho, department of Tumbes, Peru (S3.81244, W80.26716; 481 m). DHMECN 8976, juvenile collected by Michael Harvey and Luis A. Oyagata at Cerro San Sebastián, Parque Nacional Machalilla, province of Manabí, Ecuador (S1.60002, W80.69974, 602 m). DHMECN 9483, adult male collected by Mario Yánez-Muñoz, María Pérez, Miguel Alcoser, Marco Reyes-Puig and Gabriela Bautista in 2012 at the type locality. DHMECN 10061, adult male collected by Manuel Morales, María Perez Lara and Karem López at Reserva Biológica Ayampe, province of Manabí, Ecuador (S1.65417, W80.81333; 43 m). DHMECN 11526, adult of undetermined sex collected by Juan Carlos Sánchez-Nivicela, Karem López, Verónica Urgilés, Bruno Timbe, Elvis Celi and Valentina Posse at Remolino, province of El Oro, Ecuador (S3.56551, W79.91948; 229 m). KU 152205, adult of undetermined sex collected at 30 km E Pasaje, province of Azuay, Ecuador (S3.31439, W79.57970; 561 m). MCZ R-17099, a juvenile of undetermined sex collected at Valle del Chanchán, province of Chimborazo, Ecuador (S2.27383, W79.08735; 697 m). MCZ R-3564, a juvenile of undetermined sex collected by Samuel Walton Garman on January 1, 1875 at Daule River, province of Guayas, Ecuador (S1.87009, W80.00530; 5 m). MZUA.RE.0142, adult female collected by Jose Manuel Falcón at Sarayunga, province of Azuay, Ecuador (S3.31431, W79.58069; 552 m). MZUA.RE.0328, adult male collected by Keyko Cruz on April 04, 2016 at Jauneche, province of Los Ríos, Ecuador (S1.33333, W79.58333; 41 m). MZUA.RE.0424, adult male collected by Fausto Siavichay, Valentina Posse and Xavier Clavijo on June 29, 2017 at 2 km N Palmales Nuevo, province of El Oro, Ecuador (S3.65158, W80.09625; 129 m). MZUTI 3269, adult male collected by Lucas Bustamante on November 07, 2013 at the type locality. QCAZ 14444, adult male collected by Fernando Ayala, Steven Poe and Chris Anderson on January 10, 2016 at Proyecto Minas San Francisco, province of Azuay, Ecuador (S3.30829, W79.47079; 862 m). QCAZ 14446, adult male collected by Fernando Ayala, Steven Poe and Chris Anderson on January 10, 2016 at Ponce Enríquez–El Coca, province of Azuay, Ecuador (S3.03197, W79.64615; 1206 m). ZSFQ D503, adult male collected by Diego Cisneros-Heredia on June 07, 2000 at Cerro La Mocora, Parque Nacional Machalilla, province of Manabí, Ecuador (S1.60379, W80.70191; 818 m). 
DiagnosisDiagnosis. Sibon bevridgelyi is placed in the genus Sibon based on phylogenetic evidence (Fig. 3) and on having the labial beneath primary temporal conspicuosly higher than other labials. The species differs from all described species of Sibon based on the following combination of characters: (1) 15/15/15 smooth dorsals with enlarged vertebral row (1.3–1.7 times as wide as adjacent rows); (2) seven supralabials with 4th and 5th contacting orbit or eight supralabials with 5th and 6th contacting orbit; (3) one pair of infralabials in contact behind symphysial; (4) postmental absent; (5) 175–193 ventrals in males, 193 in the single female; (6) 80–94 divided subcaudals in males, 98 in the single female; (7) dorsal and ventral ground color pale yellow with or without irregular black bands, and with a black stippled disruptive pattern of irregular rusty to reddish brown blotches that are separated from each other by light interspaces (Figs 6, 2b, c); bands incomplete and stippling not prominent or absent on ventral surfaces; head heavily speckled or blotched with black or rusty pigment; eyes light slate blue to pale goldenrod with black speckles and reticulations; (8) 349–732 mm SVL in males, 786 mm in the single female; (9) 124–268 mm TL in males, 204 mm in the single female.

Comparisons. Sibon bevridgelyi is most similar to S. nebulatus, from which it differs on the basis of its distinctive coloration (Figs 6, 2b, c). In S. nebulatus (Figs 2e, f ), the dorsal and ventral color is a combination of mainly black to dark-brown blotches or bands on a gray to grayish brown background (interblotch) color; the dorso-lateral blotches can partly be bordered by white to rosy scales or edges. In some regions, the blackish pattern and gray ground color is often replaced by dark and light brown tones (e.g., in Venezuela, adjacent regions in Colombia, and Trinidad and Tobago); the spaces between the blotches are heavily invaded by blotch color and strongly stippled, spotted and mottled with white and black pigment. Although S. bevridgelyi also has a disruptive pattern, the diagnostic white and gray pigment of S. nebulatus from Central America and northern South America is lacking in S. bevridgelyi. Instead of white pigment, there is golden yellow; instead of gray, the dominant ground color is bright rusty brown to maroon. Additionally, the infralabials and the whitish throat in S. nebulatus from Central America and northern South America are heavily stippled or at least partly interrupted with black pigment, whereas in S. bevridgelyi the infralabials and the throat are immaculate or have few scattered blotches (Fig. 7b). Finally, the black blotches and stippling diagnostic of S. nebulatus are lacking in the majority of the specimens of S. bevridgelyi. Specimens of S. nebulatus with rosy gray or reddish brown ground color have white (instead of yellowish) blotches and stippling. Genetic divergence in a 521 bp long fragment of the mitochondrial Cytb gene between S. bevridgelyi and S. nebulatus leucomelas is 1.9–2.5%, whereas intraspecific distances are less than 0.4% in both species. 
CommentHabitat: arboreal vegetation 30–500 cm above the ground in secondary and primary semideciduous foothill forest, pastures, and cacao plantations, usually close to streams. By daytime, one individual (not collected) was found hidden under tree bark, and another (ZSFQ D503) was found coiled on the center of a palm tree about 2 m above the ground.

Diet: QCAZ 14444 was found feeding on a snail. In captivity, MZUA.RE.0142 fed on slugs and snails.

Sympatry: Dipsas andiana, D. bobridgelyi

Conservation status. We consider Sibon bevridgelyi to be Vulnerable following B2a,b(i,iii) IUCN criteria (IUCN 2001) because its area of occupancy is estimated to be less than 2,000 km2, it is known only from 15 patches of forest lacking connectiv- ity between them, and its habitat is severely fragmented and declining in extent and quality due to deforestation. Furthermore, only three of the localities (Parque Nacional Machalilla, Reserva Buenaventura, and Reserva Ayampe) where S. bevridgelyi occurs are currently protected. 
EtymologyThe specific epithet honors the late Prof. Beverly S. Ridgely, life-long birder and conservationist, and father of Robert S. Ridgely, well known in Ecuadorian ornithological circles and co-author of The Birds of Ecuador. Though he never got to visit Buenaventura, from afar Bev continued to delight in the conservation successes of Fundación Jocotoco, which now owns and manages one of the few protected areas where the Vulnerable Sibon bevridgelyi is known to occur. 
  • Arteaga A, Salazar-Valenzuela D, Mebert K, Peñafiel N, Aguiar G, Sánchez-Nivicela JC, Pyron RA, Colston TJ, Cisneros-Heredia DF, Yánez-Muñoz MH, Venegas PJ, Guayasamin JM, Torres-Carvajal O 2018. Systematics of South American snail-eating snakes (Serpentes, Dipsadini), with the description of five new species from Ecuador and Peru. ZooKeys 766: 79-147 - get paper here
  • Kwet, A. 2019. Liste der im Jahr 2018 neu beschriebenen Reptilien. Elaphe 2019 (3): 52-72
  • Torres-Carvajal O, Pazmiño-Otamendi G, Salazar-Valenzuela D. 2019. Reptiles of Ecuador: a resource-rich portal, with a dynamic checklist and photographic guides. Amphibian & Reptile Conservation 13 (1): [General Section]: 209–229 (e178) - get paper here
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