Published August 4, 2021. Updated May 2, 2024. Open access.

Gallery ❯

Mottled Watersnake (Helicops pastazae)

Reptiles of Ecuador | Serpentes | Colubridae | Helicops pastazae

English common names: Mottled Watersnake, Olive Watersnake, Shreve’s Keelback.

Spanish common name: Culebra acuática moteada, culebra de agua de Pastaza.

Recognition: ♂♂ 66.5 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=41.5 cm. ♀♀ 54.4 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=43.4 cm..1,2 Helicops pastazae can be distinguished from most Amazonian snakes by having dorsally oriented eyes and nostrils, a single internasal scale, round pupils, and keeled dorsal scales arranged in 23–25 rows at mid-body.1,3 The dorsum is grayish brown to tan brown with a series of broad mid-dorsal blotches alternating with smaller lateral blotches (Fig. 1).3 The belly has a chessboard pattern of black marks on a cream background.3 Juveniles usually have an incomplete pale neck band as well as a cream coloration that encompasses the muzzle and the angle of the jaw.3 This species differs from H. petersi by having a higher number of dorsal scale rows, a blunt snout, and a different color pattern.3 In H. pastazae the lateral blotches are distinctly smaller than the mid-dorsal ones. Helicops pastazae differs from H. angulatus, H. hagmanni, Hydrops martii, and H. triangularis by having keeled dorsal scales arranged in 23–25 rows at mid-body, more than 67 subcaudal scales, and a non-banded pattern.1,3

Figure showing variation among individuals of Helicops pastazae

Figure 1: Individuals of Helicops pastazae from Ecuador: Yasuní National Park, Orellana province (); Gareno Lodge, Napo province (). ad=adult, j=juvenile.

Natural history: Helicops pastazae is a semi-aquatic snake that inhabits lentic bodies of water in areas of lowland and foothill rainforest. This species is found in streams, rivers, black water lagoons, and ponds in open as well as forested areas with various degrees of human intervention.46 It also occurs in swamps dominated by the palm Mauritia flexuosa.7 Mottled Watersnakes are nocturnal, but can occasionally be active during the daytime.8 They are aquatic and can be found at different depths. When in shallow waters, individuals usually have the body submerged and part of the head above the surface.8 Mottled Watersnakes move not only in water but also on mud and soil close to water bodies.9 During the daytime, individuals have been found hidden under rocks.10 Mottled Watersnakes are sit-and-wait foragers whose only recorded prey items are fish and tadpoles.5,11 It has been hypothesized that these snakes are opportunistic predators, visiting fish nets where they can more easily capture food.12 The typical defense behavior consists of making an S-coil, flattening the body and head dorsoventrally, and striking.10 When manipulated, they rotate the body, bite, and produce cloacal discharges.8,10 This species is oviparous. In Colombia, a clutch of 11 eggs was found buried under sand and decomposing material under a large rock.10 The hatchlings measured 14.9–18.6 cm in total length.10

Reader support helps us keep the Reptiles of Ecuador book 100% free.

Conservation: Least Concern Believed to be safe from extinction given current circumstances..7,13,14 Helicops pastazae is listed in this category given its wide distribution, occurrence in protected areas, lack of widespread threats, and tolerance to human-modified environments.7 Mottled Watersnakes inhabiting polluted water bodies are known to bioaccumulate heavy metals such as lead, cadmium, and chromium, but it is unclear how the contamination of their tissues affects their survival.2

Distribution: Helicops pastazae is widely distributed throughout the western Amazon lowlands and adjacent Andean foothills in Colombia, Ecuador (Fig. 2), Peru, and Venezuela. In Colombia and Venezuela, the species has been recorded mostly along the eastern Andean Piedmont.

Distribution of Helicops pastazae in Ecuador

Figure 2: Distribution of Helicops pastazae in Ecuador. The star corresponds to the type locality: Río Pastaza. See Appendix 1 for a complete list of the presence localities included in the map.

Etymology: The generic name Helicops, which comes from the Greek words helix (=turned) and ops (=eye),15 refers to the direction of the eyes in this group of snakes, oriented not directly outwards, but obliquely upwards.16,17 The specific epithet pastazae refers to the type locality: Pastaza river.

See it in the wild: Prime locations to find Helicops pastazae in the wild in Ecuador are Yasuní Scientific Station, Tiputini Biodiversity Station, and Mandaripanga Lodge. The snakes are most easily found at night by walking along shallow muddy water bodies having abundant fish.

Special thanks to Taz Waugh for symbolically adopting the Mottled Watersnake and helping bring the Reptiles of Ecuador book project to life.

Click here to adopt a species.

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: Khamai Foundation, Quito, Ecuador.

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

How to cite? Arteaga A (2024) Mottled Watersnake (Helicops pastazae). In: Arteaga A, Bustamante L, Vieira J (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: DOI: 10.47051/SQDS6134

Literature cited:

  1. Schöneberg Y, Köhler G (2021) Distribution and identification of the species in the genus Helicops Wagler, 1830 (Serpentes, Colubridae, Xenodontinae). ARPHA Preprints 1: e67869. DOI: 10.3897/arphapreprints.e67869
  2. Hurtado-Morales MJ, Rodríguez M, Amézquita A (2021) Heavy metal concentration in Neotropical Aquatic Snakes (Helicops pastazae) and its potential as a bioindicator of water pollution. Research Square 1: 1–15. DOI: 10.21203/
  3. Rossman DA (1976) Revision of the South American colubrid snakes of the Helicops pastazae complex. Occasional papers of the Museum of Zoology, Louisiana State University 50: 1–15.
  4. Whitworth A, Beirne C (2011) Reptiles of the Yachana Reserve. Global Vision International, Exeter, 130 pp.
  5. Almendáriz A, Barriga R, Rivadeneira D (2017) Feeding behavior of Helicops pastazae Shreve 1934 (Serpentes, Colubridae, Dipsadinae) in the Ecuadorian Amazon. Herpetology Notes 10: 449–451.
  6. Cortes-Ávila L, Toledo JJ (2013) Estudio de la diversidad de serpientes en áreas de bosque perturbado y pastizal en San Vicente del Caguán (Caquetá), Colombia. Actualidades Biológicas 35: 185–197.
  7. Cisneros-Heredia DF, Ortega A, Rivas G, Calderón M, Muñoz A, Embert D, Aparicio J, Aguayo R (2016) Helicops pastazae. The IUCN Red List of threatened species. Available from: DOI: 10.2305/IUCN.UK.2016-1.RLTS.T15179049A15179095.en
  8. Field notes, Reptiles of Ecuador book project.
  9. Photo by Luis Silva Villa.
  10. García-Cobos D, Gómez-Sánchez DA (2019) Reproductive mode and defensive behaviour of the South American aquatic snake Helicops pastazae (Serpentes: Dipsadidae). Herpetology Notes 12: 447–451.
  11. Muñoz-Saba Y, Calvo-Roa N, Gómez-Sandoval PA, Casallas-Pabón D, Lynch JD, Barrientos LS, Gómez-Sánchez DA (2019) Guía de campo de los mamíferos, anfibios y reptiles de Santa María (Boyacá, Colombia). Serie Guías de Campo del Instituto de Ciencias Naturales, Bogotá, 317 pp.
  12. Field notes of Ramiro Barriga and Francisco Provenzano.
  13. Reyes-Puig C (2015) Un método integrativo para evaluar el estado de conservación de las especies y su aplicación a los reptiles del Ecuador. MSc thesis, Pontificia Universidad Católica del Ecuador, 73 pp.
  14. Morales-Betancourt MA, Lasso CA, Páez VP, Bock BC (2005) Libro rojo de reptiles de Colombia. Instituto de Investigación de Recursos Biológicos Alexander von Humboldt, Bogotá, 257 pp.
  15. Brown RW (1956) Composition of scientific words. Smithsonian Books, Washington D.C., 882 pp.
  16. Wagler JG (1830) Natürliches System der Amphibien: mit vorangehender Classification der Säugetiere und Vögel: ein Beitrag zur vergleichenden Zoologie. J.G. Cotta'scchen, München, 354 pp. DOI: 10.5962/bhl.title.58730
  17. Duméril AMC, Bibron G, Duméril AHA (1854) Erpétologie générale ou Histoire Naturelle complète des Reptiles. Librairie Encyclopédique de Roret, Paris, 780 pp. DOI: 10.5962/bhl.title.45973

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

ColombiaCaquetáFlorenciaRossman 1976
ColombiaPutumayoPuerto AsísRossman 1976
ColombiaPutumayoPuerto BoyRossman 1976
EcuadorMorona SantiagoEstación Biológica WisuiChaparro et al 2011
EcuadorMorona SantiagoMacumaRossman 1976
EcuadorMorona SantiagoRío LlushinRossman 1976
EcuadorNapoGareno LodgeThis work; Fig. 1
EcuadorNapoHuaorani LodgeReptiles of Ecuador book database
EcuadorNapoYachana ReserveWhitworth & Beirne 2011
EcuadorOrellanaCampo ShiripunoPhoto by Néstor Acosta
EcuadorOrellanaDescansoiNaturalist; photo examined
EcuadorOrellanaEl CocaDiego Piñán, pers. comm.
EcuadorOrellanaEstación Experimental de la AmazoníaPhoto by Paul Szekely
EcuadorOrellanaGuiyeroReptiles of Ecuador book database
EcuadorOrellanaMandaripanga LodgeReptiles of Ecuador book database
EcuadorOrellanaNuevo RocafuerteTorres-Carvajal et al. 2019
EcuadorOrellanaRío HiginioPhoto by Kary Hernández
EcuadorOrellanaRío RosaPazmiño-Otamendi & Rodríguez-Guerra 2022
EcuadorOrellanaTiputini Biodiversity StationiNaturalist; photo examined
EcuadorOrellanaTiputini RiverAlmendáriz et al. 2017
EcuadorOrellanaWaorani lagoonAlmendáriz et al. 2017
EcuadorOrellanaYarina LodgeReptiles of Ecuador book database
EcuadorOrellanaYasuní Scientific StationThis work; Fig. 1
EcuadorPastazaAndoasAMNH 49094; VertNet
EcuadorPastazaBloque 10-Agip OilTorres-Carvajal et al. 2019
EcuadorPastazaCabeceras del Río BobonazaRossman 1976
EcuadorPastazaCabeceras del Río Bobonaza, 2 km downstream fromRossman 1976
EcuadorPastazaCanelosRossman 1976
EcuadorPastazaChichirotaRossman 1976
EcuadorPastazaCobaya CochaAMNH 49160; VertNet
EcuadorPastazaCusuimeOrtega-Andrade 2010
EcuadorPastazaGuacheAMNH 49094; VertNet
EcuadorPastazaHeadwaters of Río CapahuariRossman 1976
EcuadorPastazaJandiayacuReptiles of Ecuador book database
EcuadorPastazaMeraRossman 1976
EcuadorPastazaMontalvoRossman 1976
EcuadorPastazaPomonaPazmiño-Otamendi & Rodríguez-Guerra 2022
EcuadorPastazaPucayacu (Río Pucayacu)Rossman 1976
EcuadorPastazaRío Arajuno, headwaters ofRossman 1976
EcuadorPastazaRío BobonazaAMNH 49053; VertNet
EcuadorPastazaRío BufeoRossman 1976
EcuadorPastazaRío ChambiraAMNH 49131; VertNet
EcuadorPastazaRío ConamboRossman 1976
EcuadorPastazaRío CopatazaRossman 1976
EcuadorPastazaRío Copataza, mouth ofRossman 1976
EcuadorPastazaRío HuiyayacuRossman 1976
EcuadorPastazaRío LliquinoRossman 1976
EcuadorPastazaRío OglánRossman 1976
EcuadorPastazaRío Pastaza*Shreve 1934
EcuadorPastazaRío PindoRossman 1976
EcuadorPastazaRío PuyoRossman 1976
EcuadorPastazaRío RutunoRossman 1976
EcuadorPastazaRío VillanoRossman 1976
EcuadorPastazaSanta Rosa, Río TigreAMNH 49172; VertNet
EcuadorPastazaSarayacuRossman 1976
EcuadorPastazaShelliNaturalist; photo examined
EcuadorPastazaVillanoReptiles of Ecuador book database
EcuadorSucumbíosDureno, 10 km N ofiNaturalist; photo examined
EcuadorSucumbíosLago AgrioPhoto by John Castillo
EcuadorSucumbíosSan Pablo de KantesiyaMHNG 2398.007; collection database
EcuadorSucumbíosSanta ElenaiNaturalist; photo examined
PerúAmazonasAguaruna VillageMVZ 163277; VertNet
PerúAmazonasChigkan EntseUSNM 260765; VertNet
PerúAmazonasChiriaco, 20 km SW ofRossman 1976
PerúAmazonasPongo MoriMVZ 163280; VertNet
PerúAmazonasSua, Río CenepaUSNM 260766; VertNet
PerúAmazonasTseasimUSNM 260763; VertNet
PerúLoretoGuacheAMNH 113660; VertNet
PerúLoretoPuesto TarquiAMNH 57342; VertNet