Published April 24, 2024. Open access.

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Black Halloween Snake (Pliocercus euryzonus)

Reptiles of Ecuador | Serpentes | Colubridae | Pliocercus euryzonus

English common name: Black Halloween Snake.

Spanish common name: Culebra quebradiza anillada.

Recognition: ♂♂ 56.0 cmMaximum distance from the snout to the tip of the tail. ♀♀ 79.5 cmMaximum distance from the snout to the tip of the tail..1 Pliocercus euryzonus is the only snake in the Ecuadorian coastal region having dorsal scales arranged in 17 rows at mid-body and a pattern of bold black rings separated by thin white rings (Fig. 1).1,2 Ecuadorian and Colombian populations of this species mimic the coloration of the coralsnake Micrurus mipartitus, from which they differ by lacking red bands on the tail.13 From Oxyrhopus petolarius, this species differs by having an entirely black head with bold white spots.13

Figure showing variation among individuals of Pliocercus euryzonus

Figure 1: Individuals of Pliocercus euryzonus: Canandé Reserve, Esmeraldas province, Ecuador (); Morromico, Chocó department, Colombia (). j=juvenile.

Natural history: Pliocercus euryzonus is an unusual snake in that it exhibits both diurnal and nocturnal activity.13 The species occurs in a variety of habitat types, ranging from pristine rainforests to clearings, pastures, and plantations, occurring in higher densities along marshes, swamps, and wetlands in general.13 Black Halloween Snakes are typically active at ground level or on low understory vegetation.13 Their diet includes anurans, frog eggs, salamanders, and fish.17 Black Halloween Snakes are calm, jittery, and rely mostly on their coralsnake coloration to avoid predatation.14 When grabbed, their typical defense behavior consists of musking, thrashing the body, and pressing the tail against the captor. They have a long, fragile tail that breaks off easily when grabbed, enabling the escape and survival of the snake.14 Unlike lizard tails, snake tails do not regenerate.5 Halloween Snakes are opisthoglyphous, meaning they have enlarged teeth towards the rear of the maxilla and are considered mildly venomous, but not dangerous to humans. There are recorded instance of predation on members of this species, including by snakes (Erythrolamprus mimus8), hawks,2 and domestic cats.4 Pliocercus euryzonus is oviparous. Clutches consist of 5–6 eggs and are laid so that hatching coincides with periods of increased amphibian reproduction.5,9

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Conservation: Least Concern Believed to be safe from extinction given current circumstances..10 Pliocercus euryzonus is listed in this category because the species has presumed stable populations and a wide distribution spanning many protected areas.10 However, in a studied snake community in western Panamá, the rate of occurrence of P. euryzonus declined between 1997 and 2012, probably following the collapse of anuran populations.11 In Ecuador, these snakes seem to have naturally low population densities.1

Distribution: Pliocercus euryzonus is widely distributed throughout the Mesoamerican and Chocoan lowlands and adjacent mountainous slopes from Guatemala to northwestern Ecuador (Fig. 2).

Distribution of Pliocercus euryzonus in Ecuador

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

Etymology: The genus name Pliocercus comes from the Greek pleos (=full) and kerkos (=tail),12 referring to the thick tail. The specific epithet euryzonus comes from the Greek words eurys (=broad) and zona (=belt).12 It refers to the broad black body rings.1

See it in the wild: Black Halloween Snakes can be seen at a rate of about once every few months in the general area of Mindo. They are typically encountered by scanning the forest floor along wetlands during the first hours of the night.

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

Photographer: Jose VieirabAffiliation: Tropical Herping (TH), Quito, Ecuador.,cAffiliation: ExSitu, Quito, Ecuador.

How to cite? Arteaga A (2024) Black Halloween Snake (Pliocercus euryzonus). In: Arteaga A, Bustamante L, Vieira J (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: DOI: 10.47051/NYYP6631

Literature cited:

  1. Arteaga A, Bustamante L, Guayasamin JM (2013) The amphibians and reptiles of Mindo. Universidad Tecnológica Indoamérica, Quito, 257 pp.
  2. Savage JM (2002) The amphibians and reptiles of Costa Rica, a herpetofauna between two continents, between two seas. The University of Chicago Press, Chicago, 934 pp.
  3. Lotzkat S (2014) Diversity, taxonomy, and biogeography of the reptiles inhabiting the highlands of the Cordillera Central (Serranía de Talamanca and Serranía de Tabasará) in western Panama. PhD thesis, Goethe-Universität in Frankfurt am Main, 931 pp.
  4. Field notes, Reptiles of Ecuador book project.
  5. Leenders T (2019) Reptiles of Costa Rica: a field guide. Cornell University Press, Ithaca, 625 pp.
  6. Cano J, Moreno IS, Uribe R, Ortiz J, Berrío S (2024) Biodiversidad Farallones del Citará. Available from:
  7. Vriesendorp C, Robertson JM (2007) Urotheca (Pliocercus) euryzonus (Halloween Snake): diet. Herpetological Review 38: 470–471.
  8. Kalki Y, Schramer TD (2018) Erythrolamprus mimus micrurus (Mimic False Coral Snake): diet/ophiophagy. Herpetological Review 49: 753.
  9. Photo by Benjamin Castillo.
  10. Solórzano A, Nicholson K, Chaves G, Porras LW (2016) Pliocercus euryzonus. The IUCN Red List of threatened species. Available from: DOI: 10.2305/IUCN.UK.2016-1.RLTS.T177444A1486938.en
  11. Zipkin EF, DiRenzo GD, Ray JM, Rossman S, Lips KR (2020) Tropical snake diversity collapses after widespread amphibian loss. Science 367: 814–816. DOI: 10.1126/science.aay5733
  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 Pliocercus euryzonus in Ecuador (Fig. 2). Go to the section on symbols and abbreviations for a list of acronyms used.

ColombiaNariñoBarbacoasDaza Rojas 2023
ColombiaNariñoDepartamento NariñoANSP 25582; VertNet
EcuadorCarchiChicalArteaga et al. 2013
EcuadorCarchiMayasquerPhoto by David Salazar
EcuadorCarchiParadero Sin FronterasiNaturalist; photo examined
EcuadorCarchiTobar DonosoSamec & Samec 1988
EcuadorChimborazoCumandáPhoto by Eduardo Zavala
EcuadorCotopaxiCorazónPellet 2017
EcuadorCotopaxiEl Jardín de los SueñosPhoto by Christophe Pellet
EcuadorCotopaxiLa ManáiNaturalist; photo examined
EcuadorCotopaxiLas PampasArteaga et al. 2013
EcuadorCotopaxiYakusinchiPhoto by Jane Sloan
EcuadorEl OroMarcabelíGarzón-Santomaro et al. 2019
EcuadorEl OroPiñasPhoto by Evelyn Hurtado
EcuadorEl OroUrna de BuenaventuraiNaturalist; photo examined
EcuadorEsmeraldasBilsa Biological ReserveOrtega-Andrade et al. 2010
EcuadorEsmeraldasCanandé ReserveArteaga et al. 2013
EcuadorEsmeraldasGualpiReptiles of Ecuador book database
EcuadorEsmeraldasSan LorenzoPhoto by Carl Franklin
EcuadorEsmeraldasSanta ClaraiNaturalist; photo examined
EcuadorEsmeraldasVerdecanandéReptiles of Ecuador book database
EcuadorImbaburaFinca La CascadaiNaturalist; photo examined
EcuadorManabíJama Coaque ReservePhoto by Ryan Lynch
EcuadorPichinchaAlambi, 1 km S ofArteaga et al. 2013
EcuadorPichinchaCasa ColibríiNaturalist; photo examined
EcuadorPichinchaEl Abrazo del ÁrbolArteaga et al. 2013
EcuadorPichinchaGualeaSavage & Crother 1989
EcuadorPichinchaGuanábanaSavage & Crother 1989
EcuadorPichinchaHacienda La HesperiaBrouwer 2018
EcuadorPichinchaHacienda San VicenteArteaga et al. 2013
EcuadorPichinchaMaquipucuna ReserveArteaga et al. 2013
EcuadorPichinchaMilpeArteaga et al. 2013
EcuadorPichinchaNanegalBoulenger 1894, Boulenger 1883
EcuadorPichinchaNanegalitoArteaga et al. 2013
EcuadorPichinchaRío CintoArteaga et al. 2013
EcuadorPichinchaSéptimo ParaísoArteaga et al. 2013
EcuadorPichinchaTandayapaValencia et al. 2017
EcuadorPichinchaVía a las CascadasKristian Svensson, pers. comm.
EcuadorSanto DomingoReserva OtongachiReptiles of Ecuador book database
EcuadorSanto Domingo de los TsáchilasSanto DomingoSavage & Crother 1989