Published September 13, 2021. Open access.

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Iridescent Ground Snake (Atractus iridescens)

Reptiles of Ecuador | Serpentes | Colubridae | Atractus | Atractus iridescens

English common name: Iridescent Ground Snake.

Spanish common names: Tierrera iridiscente, culebra tierrera iridiscente.

Recognition: ♂♂ 40.3 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=35.3 cm. ♀♀ 44.5 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=39.4 cm..13 The Iridescent Ground Snake (Atractus iridescens) differs from other snakes in its area of distribution by having a round head similar in width to the neck, small eyes, dorsal scales arranged in 17 rows at mid-body, no preocular scale, and a dorsal pattern consisting of irregular dark blotches with creamy borders disposed linearly on a brown ground color.14 The belly is pale yellowish with various degrees of dark pigment.1,4 Atractus iridescens is extremely similar to A. dunni, A. microrhynchus, and A. esepe, but so far, it has not been found living alongside any of these species, and is unique among them in having blotches that become gradually but noticeably smaller posteriorly.3,4 Males and females of A. iridescens are similar in size, coloration, and number of ventral and subcaudal scales.1

Figure showing variation among adult individuals of Atractus iridescens

Figure 1: Individuals of Atractus iridescens from Canandé Reserve, Esmeraldas province, Ecuador.

Natural history: UncommonUnlikely to be seen more than once every few months.. Atractus iridescens is a semi-fossorial (living underground and at ground level) snake that inhabits old-growth to moderately disturbed evergreen forests, although individuals occasionally show up in rural gardens nearby forest border.5 This species is distributed in warm (21.6–26 °C) areas of the Chocó rainforest where the annual precipitation ranges between 2539 and 3283 mm.3 Iridescent Ground Snakes are usually active at night on soil or leaf-litter on the forest floor.5 One individual was found hidden under a rock during a torrential rain.5 Based on what is know about other ground snakes, the diet of this species probably includes earthworms and slugs.6,7 Atractus iridescens relies mostly on its cryptic coloration as a primary line of defense. If handled, individuals usually just try to flee, but they can also use their sharp tail tip for poking as well as flatten their body dorsoventrally to appear larger.5

Conservation: Least Concern Believed to be safe from extinction given current circumstances..8 Atractus iridescens is listed in this category because the species is distributed over an area of the Chocó rainforest that has not been as heavily affected by deforestation. Thus, it is unlikely to be declining fast enough to qualify for a more threatened category.8 In Ecuador, three of the ten known localities of occurrence (Appendix 1) are in privately protected areas, but the remaining populations may disappear due to large-scale deforestation. The fear of snakes is also a source of mortality to individuals of this species. People in rural regions tend to kill any snake, even those not dangerous to them.5

Distribution: Atractus iridescens is native to the Chocoan lowlands and adjacent Andean foothills of northwestern Ecuador and western Colombia. The species has been recorded at elevations between 47 and 856 m (Fig. 2).

Distribution of Atractus iridescens in Ecuador

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

Etymology: The name Atractus, which is a latinization of the Greek word άτρακτος (meaning “spindle”),911 probably refers to the fact that snakes of this genus have a uniform width throughout the body and a narrow tail, resembling an antique spindle used to spin fibers. The specific epithet iridescens is derived from the Greek word iridos (meaning “rainbow”)12 and probably refers to how the color of the dorsal scales appears to change when viewed from different angles.

See it in the wild: Iridescent Ground Snakes are unlikely to be seen more than once every few months at any given locality. The two areas having the greatest number of observations are Canandé Reserve and the former Tundaloma Lodge, Esmeraldas province. The snakes may be located by scanning the forest floor and leaf-litter along trails at night or by looking under rocks and logs in pastures nearby forest border.

Acknowledgments: This account was published with the support of Secretaría Nacional de Educación Superior Ciencia y Tecnología (programa INEDITA; project: Respuestas a la crisis de biodiversidad: la descripción de especies como herramienta de conservación; No 00110378), Programa de las Naciones Unidas (PNUD), and Universidad San Francisco de Quito (USFQ).

Author: Alejandro ArteagaaAffiliation: Biodiversity Field Lab, Khamai Foundation, Quito, Ecuador.

Photographers: Jose VieiraaAffiliation: Tropical Herping (TH), Quito, Ecuador.,bAffiliation: ExSitu, Quito, Ecuador. and Sebastián Di DoménicocAffiliation: Keeping Nature, Bogotá, Colombia.

How to cite? Arteaga A (2021) Iridescent Ground Snake (Atractus iridescens). In: Arteaga A, Bustamante L, Vieira J, Guayasamin JM (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: DOI: 10.47051/JPAI7187

Literature cited:

  1. Passos P, Mueses-Cisneros JJ, Lynch JD, Fernandes R (2009) Pacific lowland snakes of the genus Atractus (Serpentes: Dipsadidae), with description of three new species. Zootaxa 2293: 1–34. DOI: 10.5281/zenodo.191476
  2. Arteaga A, Mebert K, Valencia JH, Cisneros-Heredia DF, Peñafiel N, Reyes-Puig C, Vieira-Fernandes JL, Guayasamin JM (2017) Molecular phylogeny of Atractus (Serpentes, Dipsadidae), with emphasis on Ecuadorian species and the description of three new taxa. ZooKeys 661: 91–123. DOI: 10.3897/zookeys.661.11224
  3. Mejía Guerrero MA (2018) Revisión taxonómica de las serpientes tierreras Atractus del grupo iridescens Arteaga et al. 2017. BSc thesis, Quito, Pontificia Universidad Católica del Ecuador, 67 pp.
  4. Cisneros-Heredia DF, Romero A (2015) First country record of Atractus medusa (Serpentes, Dipsadidae) in Ecuador. Herpetology Notes 8: 417–420.
  5. Field notes, Reptiles of Ecuador book project.
  6. Cisneros-Heredia DF (2005) Report of molluscivory in Atractus carrioni Parker, 1930. Herpetozoa 18: 185–186.
  7. Balestrin RL, Di-Bernardo M, Moreno AG (2007) Feeding ecology of the neotropical worm snake Atractus reticulatus in southern Brazil. The Herpetological Journal 17: 62–64.
  8. Bolívar W, Castañeda MR, Velasco J, Cisneros-Heredia DF (2017) Atractus iridescens. The IUCN red list of threatened species. Available from: DOI: 10.2305/IUCN.UK.2017-2.RLTS.T44581089A44581094.en
  9. Woodward SP, Tate R (1830) A manual of the Mollusca: being a treatise on recent and fossil shells. C. Lockwood and Company, London, 750 pp.
  10. Beekes R (2010) Etymological dictionary of Greek. Brill, Boston, 1808 pp.
  11. Duponchel P, Chevrolat L (1849) Atractus. In: d’Orbigny CD (Ed) Dictionnaire universel d'histoire naturelle. MM. Renard, Martinet et Cie., Paris, 312.
  12. 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 Atractus iridescens in Ecuador (Fig. 2). Go to the section on symbols and abbreviations for a list of acronyms used.

ColombiaNariñoVereda BerlinPassos et al. 2009
EcuadorCarchiRío BlancoEPN
EcuadorEsmeraldasBalneario CuchubíTorres-Carvajal et al. 2019
EcuadorEsmeraldasCanandé ReserveArteaga et al. 2017
EcuadorEsmeraldasEstero Las TinajasTorres-Carvajal et al. 2019
EcuadorEsmeraldasFinca de Carlos VásquezPhoto by Carlos Vásquez
EcuadorEsmeraldasReserva OtokikiArteaga et al. 2017
EcuadorEsmeraldasReserva Tesoro EscondidoMejía Guerrero 2018
EcuadorEsmeraldasTsejpiArteaga et al. 2017
EcuadorEsmeraldasTundaloma LodgeArteaga et al. 2017
EcuadorPichinchaPuerto QuitoArteaga et al. 2017