DOI10.47051/UNSB1612

Published August 10, 2021. Open access.

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Peter’s Watersnake (Helicops petersi)

Reptiles of Ecuador | Serpentes | Colubridae | Helicops | Helicops petersi

English common names: Peter’s Watersnake, Peter’s Keelback, Spiral Keelback.

Spanish common name: Culebra acuática de Peters.

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 The Peter’s Watersnake (Helicops petersi) 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 21 (rarely 23) rows at mid-body.1,2 The dorsum is grayish brown with a series of faint dark blotches.2 Females differ from males by having a shorter tail with fewer subcaudal scales.2 Helicops petersi is most similar to, and often confused with, H. pastazae. The latter differs from H. petersi by having dorsal scales arranged in 23–25 rows at mid-body, internasal scale usually separated from the frontal scale (instead of usually in contact in H. petersi), a blunt snout (instead of pointed in H. petersi), and a unique color pattern.2 In H. pastazae the lateral blotches are distinctly smaller than the mid-dorsal ones. In H. petersi, the dark ventral blotches are interrupted by a longitudinal pale stripe (absent in H. pastazae).2 Helicops petersi can be distinguished from H. angulatus, H. hagmanni, Hydrops martii, and Hydrops triangularis by having keeled dorsal scales arranged in 21–23 scales at mid-body, more than 67 subcaudal scales, and a non-banded pattern.2,3

Figure showing an individual of Helicops petersi

Figure 1: Adult individual of Helicops petersi from Suchipakari Lodge, Napo province, Ecuador.

Natural history: UncommonUnlikely to be seen more than once every few months.. Helicops petersi is a semi-aquatic snake that inhabits lentic bodies of water in areas of evergreen lowland and foothill forest. This species is found in tributaries of large lakes and rivers, including small streams and fast-flowing whitewater rivers, but also in flooded soccer courts.4,5 This species occurs in open as well as forested areas with various degrees of human intervention, including large cities such as Tena.5 Peter’s Watersnakes are nocturnal, but can occasionally be seen moving during the daytime.5–7 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.5 These snakes move not only in water but also on rocks, mud, and sand close to water bodies.5–7 During the daytime, individuals have been found buried in the sand besides rivers.1 Peter’s Watersnakes are sit-and-wait predators that feed mainly or exclusively on fish.4 Individuals have been captured in fish nets, which could indicate that members of this species are opportunistic predators of trapped fish.4 Faced with a potential threat, individuals make an S-coil, flatten the body and head dorsoventrally, open the mouth, and strike.5 When manipulated, they rotate the body, bite, and produce cloacal discharges.5 This species is probably oviparous. One gravid female contained 12 small ova.1

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Conservation: Vulnerable Considered to be facing a high risk of extinction in the mid-term future.. Helicops petersi is proposed to be included in this category, instead of Near Threatened,4 because the species is range-restricted (~9,800–10,916 km2; Fig. 2), its habitat is severely fragmented, and the rivers where it occurs are rapidly declining due to pollution. The habitat of H. petersi coincides with the most fragmented segment of the Ecuadorian Amazon rainforest and the rivers where it occurs are currently being destroyed and polluted by open-pit gold mining operations. Although there is no information on the population trend of the species, its numbers are expected to be declining alongside the increase in gold mining activities along the rivers Anzu, Tena, and Napo.

Distribution: Helicops petersi is endemic to an estimated 10,916 km2 area in the upper watershed of the Napo river in eastern Ecuador. The species has been recorded at elevations between 317 and 1112 m (Fig. 2).

Distribution of Helicops petersi in Ecuador

Figure 2: Distribution of Helicops petersi 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 Misahuallí.

Etymology: The generic name Helicops, which comes from the Greek words helix (meaning “turned”) and ops (meaning “eye”),8 refers to the direction of the eyes in this group of snakes, oriented not directly outwards, but obliquely upwards.9,10 The specific epithet petersi honors American herpetologist James A Peters (1922–1972), in recognition of his contributions to expanding the knowledge on Neotropical reptiles, particularly those from Ecuador.

See it in the wild: Peter’s Watersnakes can be located with ~3–10% certainty in forested areas through the species’ area of distribution in Ecuador, especially along slow-moving whitewater rivers. The area having the greatest number of recent observations is Río Misahuallí, near the city Tena, Napo province. The snakes are most easily found at night by walking along rocky whitewater rivers

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.

Photographer: Jose VieiraaAffiliation: Tropical Herping (TH), Quito, Ecuador.,bAffiliation: ExSitu, Quito, Ecuador.

How to cite? Arteaga A (2021) Peter’s Watersnake (Helicops petersi). In: Arteaga A, Bustamante L, Vieira J (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: www.reptilesofecuador.com. DOI: 10.47051/UNSB1612

Literature cited:

  1. Duellman WE (1978) The biology of an equatorial herpetofauna in Amazonian Ecuador. Publications of the Museum of Natural History, University of Kansas 65: 1–352.
  2. 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.
  3. 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
  4. Cisneros-Heredia DF, Almendáriz A, Valencia J (2017) Helicops petersi. The IUCN Red List of threatened species. Available from: www.iucnredlist.org. DOI: 10.2305/IUCN.UK.2017-2.RLTS.T15179117A15179121.en
  5. Field notes, Reptiles of Ecuador book project.
  6. Photo by Cristina Teruel Vilar.
  7. Photo by Jimmy Velasteguí.
  8. Brown RW (1956) Composition of scientific words. Smithsonian Books, Washington D.C., 882 pp.
  9. 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
  10. 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 petersi in Ecuador (Fig. 2). Go to the section on symbols and abbreviations for a list of acronyms used. Asterisk (*) indicates type locality.

CountryProvinceLocalitySource
EcuadorNapoFinca FischerTCWC 65022
EcuadorNapoMisahuallíPhoto by Diego Piñán
EcuadorNapoRío CotopinoRossman 1976
EcuadorNapoRio Misahuallí*Rossman 1976
EcuadorNapoSuchipakari LodgeThis work
EcuadorNapoTenaiNaturalist
EcuadorOrellanaConcepciónRossman 1976
EcuadorOrellanaMouth of Río GuataracoRossman 1976
EcuadorPastazaAlpayacuRossman 1976
EcuadorPastazaMuyu Rainforest ReserveiNaturalist
EcuadorPastazaReserva Río AnzuThis work
EcuadorPastazaRío Arajuno, headwaters ofRossman 1976
EcuadorSucumbíosPuerto LibreDuellman 1978
EcuadorSucumbíosRío AguaricoTorres-Carvajal et al. 2019
EcuadorSucumbíosSanta CeciliaDuellman 1978