Published April 16, 2024. Open access.

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Blacktail Cribo (Drymarchon melanurus)

Reptiles of Ecuador | Serpentes | Colubridae | Drymarchon melanurus

English common names: Blacktail Cribo, Central American Indigo Snake.

Spanish common name: Guaso, sayama, colambo, rabo negro.

Recognition: ♂♂ 295.0 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=245.0 cm. ♀♀ 281.5 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=241.0 cm..1 Drymarchon melanurus is a heavy-bodied snake having a unique dorsal coloration. The head and about two thirds of the dorsum have a pale brown hue, gradually darkening posteriorly, with the tail being completely black (Fig. 1). Three black stripes emerge from the eyes towards the supralabial scales, with a fourth one occasionally being present on the last supralabial scale.26 On each side of the neck, black scales form a diagonal line. The juvenile pattern is similar, but may also include dark oblique crossbars along the dorsum. The ventral area is creamy yellow with dark transverse lines, becoming progressively darker towards the tail.26 This species differs from other large diurnal snakes (such as Chironius, Spilotes and Phrynonax) by having smooth dorsal scales. From Clelia clelia, it differs by having a brown dorsum.7

Figure showing variation among individuals of Drymarchon melanurus

Figure 1: Individuals of Drymarchon melanurus from Ecuador: Cahuasquí, Imbabura province (); Azuay province (). j=juvenile.

Natural history: Drymarchon melanurus is a primarily terrestrial snake that inhabits a variety of forested and semi-open ecosystems, ranging from pristine seasonally dry forests to pastures and cultivated areas.2,49 In xeric habitats, the species occurs in higher densities along bodies of water, including water channels, swampy areas, and rivers, with individuals frequently seen swimming across the water surface.8 Blacktail Cribos forage primarily on the forest floor during sunny days, but they also ascend to low vegetation or onto boulders to bask and forage.2,810 They are active foragers that subdue prey with a firm bite. The diet in this species includes a wide variety of amphibians (even toxic ones such as Rhinella bella, although the snake may die as a result of the ingestion8,11), birds and their eggs, hawks, swamp eels,12 lizards, turtles (Rhinoclemmys nasuta), small mammals, and snakes (including Boa imperator,8,13 Bothrops asper,13 Spilotes pullatus,14 and Micrurus dumerilii14).24,16 It is hypothesized that D. melanurus is immune to the venom of vipers, given its ability to consume them, although studies to prove this are still lacking. This snake exhibits aggressive behavior when cornered, opening its mouth with the neck region extended while striking repeatedly, sometimes lashing with the tail.6 There are a recorded instance of predation on members of this species, including by hawks and the mustelid Galictis vittata.4,17 Drymarchon melanurus is an oviparous reptile that lays clutches of 4–25 eggs during the local dry season,4 with incubation lasting approximately three months.18 Male-male combat occurs as part of the courtship ritual in this species.18

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Conservation: Least Concern Believed to be safe from extinction given current circumstances..19 Drymarchon melanurus is listed in this category mainly on the basis of the species’ wide distribution, lack of major widespread threats, and presumed stable populations.19 However, individuals of D. melanurus suffer from traffic mortality20 and direct killing.8 However, these reptiles are appreciated and even protected in some farming communities for their tendency to feed on venomous snakes as well as on pests such as rats and mice.8

Distribution: Drymarchon melanurus is widely distributed throughout the Neotropics, from Mexico to Ecuador (Fig. 2) and northwestern Peru.

Distribution of Drymarchon melanurus in Ecuador

Figure 2: Distribution of Drymarchon melanurus in Ecuador. See Appendix 1 for a complete list of the presence localities included in the map.

Etymology: The genus name Drymarchon is derived from the Greek drymos (=oak forest) and archon (=leader),21 and probably refers to the imposing size of this snake. The specific epithet melanurus comes from the Greek words melas (=black) and oura (=tail).21

See it in the wild: Drymarchon melanurus is considered an uncommon species in Ecuador, with no more than 1–2 individuals recorded per month at any given locality. The area having the greatest number of observations of this elusive serpent is Bosque Protector Cerro Blanco.

Special thanks to Jennifer Krajcir for symbolically adopting the Blacktail Cribo and helping bring the Reptiles of Ecuador book project to life.

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Authors: Tatiana Molina-Moreno,aAffiliation: Departamento de Biología, Universidad de los Llanos, Villavicencio, Colombia. Andrés F. Aponte-Gutiérrez,bAffiliation: Grupo de Investigación en Ciencias de la Orinoquía, Universidad Nacional de Colombia sede Orinoquía, Arauca, Colombia.,cAffiliation: Fundación Biodiversa Colombia, Bogotá, Colombia. and Danna Duque-TorresdAffiliation: Grupo de Ornitología, Universidad Nacional de Colombia, Bogotá, Colombia.

Editor: Alejandro ArteagaeAffiliation: Tropical Herping (TH), Quito, Ecuador.

Photographer: Jose VieirafAffiliation: Tropical Herping (TH), Quito, Ecuador.,gAffiliation: ExSitu, Quito, Ecuador.

How to cite? Molina-Moreno T, Aponte-Gutierrez AF, Duque-Torres D (2024) Blacktail Cribo (Drymarchon melanurus). In: Arteaga A, Bustamante L, Vieira J (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: DOI: 10.47051/MOSF2794

Literature cited:

  1. Duellman WE (1960) A record size for Drymarchon corais melanurus. Copeia 1960: 367–368.
  2. Heimes P (2016) Snakes of Mexico. Chimaira, Frankfurt, 572 pp.
  3. Guerra D, Fuentes R, Morán D (2012) Serpientes de Guatemala: guía para identificación de especies. Universidad de San Carlos de Guatemala, Ciudad de Guatemala, 186 pp.
  4. Savage JM (2002) The amphibians and reptiles of Costa Rica, a herpetofauna between two continents, between two seas. The University of Chicago Press, Chicago, 934 pp.
  5. Lotzkat S (2014) Diversity, taxonomy, and biogeography of the reptiles inhabiting the highlands of the Cordillera Central (Serranía de Talamanca and Serranía de Tabasará) in western Panama. PhD thesis, Goethe-Universität in Frankfurt am Main, 931 pp.
  6. La Marca E, Soriano PJ (2004) Reptiles de los Andes de Venezuela. Fundación Polar, Mérida, 173 pp.
  7. Peters JA, Orejas-Miranda B (1970) Catalogue of Neotropical Squamata: part I, snakes. Bulletin of the United States National Museum, Washington, D.C., 347 pp.
  8. Field notes, Reptiles of Ecuador book project.
  9. Almendáriz A, Brito J (2011) Biodiversidad de los valles secos interandinos del Ecuador. Escuela Politécnica Nacional, Quito, 60 pp.
  10. Rodríguez-Canseco JM, Gozález-Estupiñán KL, López-Rodríguez LE (2013) Drymarchon melanurus (Central American Indigo Snake): distribution. Herpetological Review 44: 476.
  11. Photo by Juan Camilo Montoya Gallego.
  12. Sunyer J, Leonardi R (2015) Drymarchon melanurus (Central American Indigo Snake): diet. Herpetological Review 46: 103.
  13. Duellman WE (1983) Amphibians and reptiles of the rainforests of souther El Petén, Guatemala. Miscellaneous Publications of the Museum of Natural History, University of Kansas 15: 205–249.
  14. Oakley J, Theodorou A (2020) A failed predation attempt by a Central American Indigo Snake (Drymarchon melanurus) on a Tiger Ratsnake (Spilotes pullatus) in Campeche, Mexico. Reptiles & Amphibians 27: 494–495.
  15. Zúñiga-Baos JA, Vera-Pérez LE (2020) Drymarchon melanurus (Central American Indigo Snake): diet. Herpetological Review 51: 864.
  16. Scott NJ (1983) Drymarchon corais (zopilota, indigo). In: Janzen DH (Ed) Costa Rican natural history. The University of Chicago Press, Chicago, 398–399.
  17. Hidalgo-Mihart MG, Juárez-López R, Contreras-Moreno F, De La Cruz AJ, López-Luna MA, De La Cruz YB (2018) Greater grison (Galictis vittatta) hunts a central American indigo snake (Drymarchon melanurus) in Southeastern Mexico. The Southwestern Naturalist 63: 197–199.
  18. Leenders T (2019) Reptiles of Costa Rica: a field guide. Cornell University Press, Ithaca, 625 pp.
  19. Gutiérrez-Cárdenas P, Rivas G (2019) Drymarchon melanurus. The IUCN Red List of threatened species. Available from: DOI: 10.2305/IUCN.UK.2017-2.RLTS.T63774A3129309.en
  20. Gaón Rojas JE, Valdez Cusme GP (2021) Mortalidad de la fauna silvestre por efecto vehicular en la carretera Calceta-Quiroga. BSc thesis, Escuela Superior Politécnica Agropecuaria de Manabí Manuel Feliz López, 127 pp.
  21. Brown RW (1956) Composition of scientific words. Smithsonian Books, Washington D.C., 882 pp.

Appendix 1: Locality data used to create the distribution map of Drymarchon melanurus in Ecuador (Fig. 2). Go to the section on symbols and abbreviations for a list of acronyms used.

ColombiaHuilaReserva PompeyaiNaturalist; photo examined
ColombiaHuilaSan AgustíniNaturalist; photo examined
ColombiaNariñoGuayabaliNaturalist; photo examined
EcuadorAzuayChilcaplayaMZUA.RE.0099; examined
EcuadorAzuayFinca Los MangosPhoto by Ernesto Arbeláez
EcuadorAzuayJubonesiNaturalist; photo examined
EcuadorAzuayLentagKU 152203; VertNet
EcuadorAzuayPoetateReptiles of Ecuador book database
EcuadorAzuayTamarindoJuan Carlos Sánchez, pers. comm.
EcuadorCañarFinca HuatacónReptiles of Ecuador book database
EcuadorEl OroCaliforniaReptiles of Ecuador book database
EcuadorEl OroChillaRodríguez-Guerra & Guerra-Correa 2020
EcuadorEl OroLa CucaPhoto by Pablo Loaiza
EcuadorEl OroLa VictoriaiNaturalist; photo examined
EcuadorEl OroPasajeiNaturalist; photo examined
EcuadorEl OroPiedrasiNaturalist; photo examined
EcuadorEl OroPortoveloKU 164213; VertNet
EcuadorEl OroReserva Biológica BuenaventuraPhoto by David Agro
EcuadorEsmeraldasSan Miguel de los BancosMHNG 2221.026; collection database
EcuadorGuayasBosque Protector Cerro BlancoJean Thomas Bujard
EcuadorGuayasCapeiraPhoto by Eduardo Zavala
EcuadorGuayasCerro de HayasPhoto by Luis Oyagata
EcuadorGuayasChongónReptiles of Ecuador book database
EcuadorGuayasGuayaquil, Albarrada MonoCJ-PMH-898; VertNet
EcuadorGuayasGuayaquil, BellavistaiNaturalist; photo examined
EcuadorGuayasHacienda La DanesaPhoto by Klaus Fielsch
EcuadorGuayasIsla SantayCruz-García et al. 2023
EcuadorGuayasLago de la EspoliNaturalist; photo examined
EcuadorGuayasLomas de SargentilloiNaturalist; photo examined
EcuadorGuayasMachalaReptiles of Ecuador book database
EcuadorGuayasMilagro, 7 km NW ofiNaturalist; photo examined
EcuadorGuayasPocos PalosiNaturalist; photo examined
EcuadorGuayasSalitre, 1 km W ofiNaturalist; photo examined
EcuadorGuayasSamborondóniNaturalist; photo examined
EcuadorGuayasVeneciaiNaturalist; photo examined
EcuadorGuayasZoo el PantanalReptiles of Ecuador book database
EcuadorImbaburaCahuasquíThis work; Fig. 1
EcuadorImbaburaCarolinaUMMZ 132632; VertNet
EcuadorImbaburaIbarraPhoto by Diego Piñán
EcuadorImbaburaLa PeñaiNaturalist; photo examined
EcuadorImbaburaSan RoqueRodríguez-Guerra & Guerra-Correa 2020
EcuadorImbaburaSector CabuyalAlmendariz & Brito 2011
EcuadorImbaburaUniversidad YachayiNaturalist; photo examined
EcuadorLojaEl IngenioiNaturalist; photo examined
EcuadorLojaHacienda De JuanesUSNM 98934; VertNet
EcuadorLojaJorupe ReserveReptiles of Ecuador book database
EcuadorLojaLa CaleraiNaturalist; photo examined
EcuadorLojaPindalMHNG 2442.061; collection database
EcuadorLojaQuebrada BuenavistaReptiles of Ecuador book database
EcuadorLojaSan PedroRodríguez-Guerra & Guerra-Correa 2020
EcuadorLojaValle del CatamayoParker 1938
EcuadorLojaVilcabambaReptiles of Ecuador book database
EcuadorLos RíosBosque Protector Pedro Franco DávilaCruz & Sánchez 2016
EcuadorLos RíosHostería El Señor de los CaballosThis work; Fig. 1
EcuadorManabíCalcetaMHNG 2399.008; collection database
EcuadorManabíCalceta–Quiroga roadGaón Rojas & Valdez Cusme 2021
EcuadorManabíLas TunasPhoto by Edison Araguillin
EcuadorManabíRancho San JuaniNaturalist; photo examined
EcuadorManabíReserva Jama CoaqueiNaturalist; photo examined
EcuadorManabíTosaguaPhoto by Gustavo Macías
EcuadorPichinchaAsociación Las TangarasiNaturalist; photo examined
EcuadorPichinchaHacienda La HesperiaBrouwer 2018
EcuadorPichinchaPedro Vicente MaldonadoiNaturalist; photo examined
EcuadorPichinchaPorvenirValencia et al. 2017
EcuadorPichinchaReserva MaquipucunaiNaturalist; photo examined
EcuadorSanta ElenaSamay Ocean Lodge SpaiNaturalist; photo examined
EcuadorSanto Domingo de los TsáchilasBosque Protector La PerlaUSNM 204119; VertNet
EcuadorSanto Domingo de los TsáchilasSan Miguel de los coloradosUSNM 204118; VertNet
PeruCajamarcaEl ChorroMCZ 178178; VertNet
PeruPiuraHacienda San MartíniNaturalist; photo examined
PeruPiuraPalo BlancoVásquez Calle 2018
PeruTumbesCabo IngaTello 1998