Published August 4, 2021. Open access.

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Mottled Watersnake (Helicops pastazae)

Reptiles of Ecuador | Serpentes | Colubridae | Helicops | 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 The Mottled Watersnake (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.3 The belly has a chessboard pattern of black marks on a cream background.3 Females differ from males by having a shorter tail with fewer subcaudal scales.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 In Ecuador, H. pastazae is most similar to, and often confused with, H. petersi. The latter differs from H. pastazae by having dorsal scales arranged in 21 (rarely 23) rows at mid-body, internasal scale usually in contact with the frontal scale (instead of usually separated in H. pastazae), a pointed snout (instead of blunt in H. pastazae), and a unique color pattern.3 In H. petersi, all dorsal blotches, mid-dorsal or lateral, are of roughly the same size, whereas in H. pastazae the lateral ones are distinctly smaller. In H. petersi, the dark ventral blotches are interrupted by a longitudinal pale stripe (absent in H. pastazae). Helicops pastazae can be distinguished from H. angulatus, H. hagmanni, Hydrops martii, and Hydrops triangularis by having keeled dorsal scales arranged in 23–25 scales 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 Yasuní National Park, Orellana province (), and Gareno Lodge, Napo province (), Ecuador. ad=adult, j=juvenile.

Natural history: FrequentRecorded weekly in densities below five individuals per locality.. Helicops pastazae is a semi-aquatic snake that inhabits lentic bodies of water in areas of evergreen lowland and foothill forest. 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 Faced with a potential threat, individuals make an S-coil, flatten the body and head dorsoventrally, open the mouth, and strike.10 When manipulated, individuals rotate the body, bite, and produce cloacal discharges.8,10 This species is oviparous. In Colombia, there is a record of a clutch of 11 eggs found buried under sand and decomposing material under a large rock.10 The hatchlings measured 14.9–18.6 cm in total length.10

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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 However, the species’ presence near urbanized areas makes individuals especially susceptible to being killed by people who confuse the snake with a venomous one. 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 basin and adjacent Andean foothills in Colombia, Ecuador, Peru, and Venezuela. In Colombia and Venezuela, the species has been recorded mostly along the eastern Andean Piedmont. In Ecuador, this species occurs at elevations between 131 and 1311 m (Fig. 2).

Distribution of Helicops pastazae in Ecuador

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

Etymology: The generic name Helicops, which comes from the Greek words helix (meaning “turned”) and ops (meaning “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: Mottled Watersnakes can be located with ~5–15% certainty in forested areas through the species area of distribution in Ecuador, especially along slow-moving whitewater rivers. Some of the best 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.

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

How to cite? Arteaga A (2021) Mottled Watersnake (Helicops pastazae). 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/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
EcuadorMorona SantiagoEstación Biológica WisuiChaparro et al 2011
EcuadorMorona SantiagoMacumaRossman 1976
EcuadorMorona SantiagoRío LlushinRossman 1976
EcuadorNapoGareno LodgeThis work
EcuadorNapoHuaorani LodgeThis work
EcuadorNapoYachana ReserveWhitworth & Beirne 2011
EcuadorOrellanaCampo ShiripunoPhoto by Néstor Acosta
EcuadorOrellanaEl CocaDiego Piñán, pers. comm.
EcuadorOrellanaEstación Experimental de la AmazoníaPhoto by Paul Szekely
EcuadorOrellanaGuiyeroThis work
EcuadorOrellanaJoya de los SachasDHMECN 4986
EcuadorOrellanaMandaripanga LodgeThis work
EcuadorOrellanaNuevo RocafuerteTorres-Carvajal et al. 2019
EcuadorOrellanaRío HiginioPhoto by Kary Hernández
EcuadorOrellanaTiputini RiverAlmendáriz et al. 2017
EcuadorOrellanaWaorani lagoonAlmendáriz et al. 2017
EcuadorOrellanaYarina LodgeThis work
EcuadorOrellanaYasuní Scientific StationThis work
EcuadorPastazaAndoasAMNH 49094
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
EcuadorPastazaCusuimeOrtega-Andrade 2010
EcuadorPastazaGuacheAMNH 49094
EcuadorPastazaHeadwaters of Río CapahuariRossman 1976
EcuadorPastazaJandiayacuThis work
EcuadorPastazaMeraRossman 1976
EcuadorPastazaMontalvoRossman 1976
EcuadorPastazaPuerto BoyRossman 1976
EcuadorPastazaPuyo, 1 km N ofiNaturalist
EcuadorPastazaRío Arajuno, headwaters ofRossman 1976
EcuadorPastazaRío BobonazaAMNH 49053
EcuadorPastazaRío BufeoRossman 1976
EcuadorPastazaRío ChambiraAMNH 49131
EcuadorPastazaRío ConamboRossman 1976
EcuadorPastazaRío CopatazaRossman 1976
EcuadorPastazaRío Copataza, mouth ofRossman 1976
EcuadorPastazaRío HuiyayacuRossman 1976
EcuadorPastazaRío LliquinoRossman 1976
EcuadorPastazaRío OglánRossman 1976
EcuadorPastazaRío PastazaRossman 1976
EcuadorPastazaRío PindoRossman 1976
EcuadorPastazaRío PucayacuRossman 1976
EcuadorPastazaRío PuyoRossman 1976
EcuadorPastazaRío RutunoRossman 1976
EcuadorPastazaRío VillanoRossman 1976
EcuadorPastazaSanta Rosa, Río TigreAMNH 49172
EcuadorPastazaSarayacuRossman 1976
EcuadorPastazaVillanoThis work
EcuadorSucumbíosDureno, 10 km N ofiNaturalist
EcuadorSucumbíosLago AgrioPhoto by John Castillo
EcuadorSucumbíosSan Pablo de KantesiyaMHNG 2398.007
EcuadorSucumbíosSanta ElenaDHMECN 7831
EcuadorSucumbíosShushufindiDHMECN 136
EcuadorTungurahuaEl TopoDHMECN 598
PeruAmazonasAguaruna VillageMVZ 163277
PeruAmazonasChigkan EntseUSNM 260765
PeruAmazonasChiriaco, 20 km SW ofRossman 1976
PeruAmazonasPongo MoriMVZ 163280
PeruAmazonasSua, Río CenepaUSNM 260766
PeruAmazonasTseasimUSNM 260763
PeruLoretoGuacheAMNH 113660
PeruLoretoPuesto TarquiAMNH 57342