Published May 19, 2022. Updated February 26, 2024. Open access.

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Giant Ground Snake (Atractus gigas)

Reptiles of Ecuador | Serpentes | Colubridae | Atractus gigas

English common name: Giant Ground Snake.

Spanish common names: Tierrera gigante, culebra de tierra gigante.

Recognition: ♂♂ 100.2 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=88.7 cm. ♀♀ 121 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=107.8 cm..1,2 Atractus gigas 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 ground color that changes throughout the snake’s lifespan.2,3 Juveniles have a contrasting pattern of dark-brown to black bands on a rosy white background color (Fig. 1). This pattern becomes fainter with age but is still noticeable in individuals as large as 35.5 cm in total length.2 Adults are almost entirely dark brown or blackish with iridescent hues.4,5 The only other ground snakes known to co-occur with A. gigas are A. dunni and A. microrhynchus, but their adults are similar in size to juveniles of A. gigas. Instead of having a banded pattern, they have a series of minute black spots or longitudinal lines on an uniform brown dorsal color.6,7 Adults of A. gigas are similar in size and coloration to those of Clelia equatoriana, but the latter can be distinguished by the presence of a preocular scale.2

Figure showing variation among individuals of Atractus gigas

Figure 1: Individuals of Atractus gigas from Birdwatcher’s House Lodge, Pichincha province, Ecuador. sa=subadult, j=juvenile, n=neonate.

Natural history: Atractus gigas is an extremely rare semi-fossorial snake that inhabits well-preserved cloud forests as well as recently created pastures, rural gardens, and shaded coffee plantations adjacent to these forests.14 Most active Giant Ground Snakes have been seen crawling on the leaf-litter on the forest floor during the early morning or in the afternoon,14 but one adult snake was climbing on branches 1.6 m above the ground at night.8 Inactive individuals have been found hidden under rocks, rotten logs, or buried underground.1,2 An adult snake was observed feeding on a giant earthworm,1 and another produced faeces that appeared to contain small mammal remains.4 These shy and docile snakes rely mostly on their cryptic coloration as a primary line of defense. If handled, they usually just try to flee, but they can also use their sharp tail tip for poking as well as flatten the body dorsoventrally to appear larger. A clutch of 11 eggs was found under a large rotten log in a pasture near forest border.1

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Conservation: Near Threatened Not currently at risk of extinction, but requires some level of management to maintain healthy populations..9 Although it is a rare species, Atractus gigas is listed in this category because it has been recorded in more than 10 localities (=20; see Appendix 1), occurs in at least seven privately protected areas, and is distributed over an area that retains most (~74%) of its forest cover.10 Therefore, the species is considered to be facing no major immediate extinction threats.9 However, some populations are likely to be declining due to deforestation by logging and large-scale mining, especially in the provinces Imbabura and Carchi.9,11

Distribution: Atractus gigas is endemic to an area of approximately 3,685 km2 along the western slopes of the Ecuadorian Andes (Fig. 2).

Distribution of Atractus gigas in Ecuador

Figure 2: Distribution of Atractus gigas in Ecuador. The star corresponds to the type locality: Bosque Protector Río Guajalito, Santo Domingo de los Tsáchilas province. 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 (=spindle),1214 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 gigas is a Latin word meaning “giant”.3 According to Greek mythology, the giants were enormous beings with thick serpents for legs. They fought a losing battle with the gods and man.3

See it in the wild: Giant Ground Snakes are unlikely to be seen more than once every few months at any give locality. Few (less than 10) have reportedly been found active while crossing forest trails or moving along the leaf-litter. However, seven individuals in addition to a clutch of eggs were found by flipping rotten logs in a recently cleared pasture during a period of two hours. The areas having the greatest number of observations of Atractus gigas are Bosque Integral Otonga and Birdwatcher’s House Lodge.

Acknowledgments: Special thansk to Vinicio Pérez for finding the adult male individual of Atractus gigas photographed in this account.

Author: Alejandro ArteagaaAffiliation: Khamai Foundation, Quito, Ecuador.

Photographers: Jose VieiraaAffiliation: Tropical Herping (TH), Quito, Ecuador.,bAffiliation: ExSitu, Quito, Ecuador. and Alejandro ArteagaaAffiliation: Khamai Foundation, Quito, Ecuador.

How to cite? Arteaga A (2024) Giant Ground Snake (Atractus gigas). In: Arteaga A, Bustamante L, Vieira J (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: DOI: 10.47051/QKCA8741

Literature cited:

  1. Field notes, Reptiles of Ecuador book project.
  2. Arteaga A, Bustamante L, Guayasamin JM (2013) The amphibians and reptiles of Mindo. Universidad Tecnológica Indoamérica, Quito, 257 pp.
  3. Myers CW, Schargel WE (2006) Morphological extremes–two new snakes of the genus Atractus from northwestern South America (Colubridae: Dipsadinae). American Museum Novitates 3532: 1–13.
  4. Tolhurst B, Peck M, Morales JN, Cane T, Recchio I (2010) Extended distribution of a recently described dipsadine colubrid snake: Atractus gigas. Herpetology Notes 3: 73–75.
  5. Passos P, Dobiey M, Venegas PJ (2010) Variation and natural history notes on giant groundsnake, Atractus gigas (Serpentes: Dipsadidae). South American Journal of Herpetology 5: 73–82. DOI: 10.2994/057.005.0201
  6. Savage JM (1960) A revision of the Ecuadorian snakes of the Colubrid genus Atractus. Miscellaneous Publications, Museum of Zoology, Univesity of Michigan 112: 1–184.
  7. 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
  8. Video by Vinicio Pérez.
  9. Cisneros-Heredia DF, Almendáriz A (2020) Atractus gigas. The IUCN Red List of threatened species. Available from: DOI: 10.2305/IUCN.UK.2020-2.RLTS.T50951103A170568823.en
  10. MAE (2012) Línea base de deforestación del Ecuador continental. Ministerio del Ambiente del Ecuador, Quito, 30 pp.
  11. Guayasamin JM, Cisneros-Heredia DF, Vieira J, Kohn S, Gavilanes G, Lynch RL, Hamilton PS, Maynard RJ (2019) A new glassfrog (Centrolenidae) from the Chocó-Andean Río Manduriacu Reserve, Ecuador, endangered by mining. PeerJ 7: e6400. DOI: 10.7717/peerj.6400
  12. 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.
  13. Beekes R (2010) Etymological dictionary of Greek. Brill, Boston, 1808 pp.
  14. Duponchel P, Chevrolat L (1849) Atractus. In: d’Orbigny CD (Ed) Dictionnaire universel d’histoire naturelle. MM. Renard, Martinet et Cie., Paris, 312.

Appendix 1: Locality data used to create the distribution map of Atractus gigas in Ecuador (Fig. 2). Go to the section on symbols and abbreviations for a list of acronyms used. Asterisk (*) indicates type locality.

EcuadorCarchiVía El Chical–GualchánMantilla Espinoza 2021
EcuadorCotopaxiBosque Integral OtongaArteaga et al. 2017
EcuadorCotopaxiPeñas ColoradasMantilla Espinoza 2021
EcuadorCotopaxiSan Francisco de Las PampasArteaga et al. 2013
EcuadorImbaburaIntagSavage 1960
EcuadorImbaburaPropiedad del Sr. Luis PompilioReptiles of Ecuador book database
EcuadorPichinchaBellavistaArteaga et al. 2013
EcuadorPichinchaBirdwatcher’s HouseThis work; Fig. 1
EcuadorPichinchaChiribogaArteaga et al. 2013
EcuadorPichinchaMindo, 3.7 km NE ofiNaturalist; photo examined
EcuadorPichinchaMindolomaEric Osterman, pers. comm.
EcuadorPichinchaReserva ArlequínReptiles of Ecuador book database
EcuadorPichinchaReserva Las GralariasArteaga et al. 2017
EcuadorPichinchaReserva Santa LucíaTolhurst et al. 2010
EcuadorPichinchaSan TadeoPhoto by Ryan Lynch
EcuadorPichinchaSaragoza–Río CintoYánez-Muñoz et al. 2009
EcuadorPichinchaTandapiArteaga et al. 2013
EcuadorPichinchaTandayapaValencia et al. 2017
EcuadorSanto Domingo de los TsáchilasBosque Protector Río Guajalito*Myers & Schargel 2006
EcuadorSanto Domingo de los TsáchilasLas PalmerasArteaga et al. 2013