Pinzón Racer

Reptiles of Ecuador | Serpentes | Colubridae | Pseudalsophis | Pseudalsophis slevini

English common names: Pinzón Racer, Slevin's Racer, Banded Galápagos Snake.

Spanish common names: Culebra de Pinzón, culebra de Slevin, serpiente corredora de Pinzón.

Recognition: ♂♂ 52.5 cm ♀♀ 41.3 cm. Pseudalsophis slevini is the only snake known to occur on Pinzón Island, and is one of two species of snakes in Galápagos having a banded pattern. The other one is the Darwin's Racer (P. darwini), which is endemic to Isabela and Fernandina islands.

Natural history: Frequent. Pseudalsophis slevini is a diurnal snake inhabiting volcanic rock areas, deciduous forests, and dry grasslands.1 Pinzón Racers are active throughout the day, but usually not during hot midday hours. They move on soil, rocks, leaf litter, and branches.1 Snakes of this species are mildly venomous, which means they are dangerous to small prey, but not to humans.2 They are foraging predators of Pinzón Leaf-toed Geckos (Phyllodactylus duncanensis) and Pinzón Lava-Lizards (Microlophus duncanensis).3,4 Individuals of P. slevini are preyed upon by hawks.5

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Conservation: Vulnerable. We consider Pseudalsophis slevini to be in this category following IUCN criteria6 because the species is restricted to an island of only 18 km2 and, therefore, is exposed to extreme population fluctuations because of random climatic or biological (for example, invasive species) events. Rats invaded Pinzón Island for nearly 200 years,7 a species that, most likely, reduced the Pinzón Racer population by preying on its eggs and juveniles. Thanks to efforts led by the Galápagos National Park, rats were finally eradicated from the island in 2012.

Special thanks to Ron Smith, our official protector of the Pinzón Racer, for symbolically adopting this species and helping bring the Reptiles of Galápagos project to life.

Distribution: Pseudalsophis slevini is endemic to the 18 km2 area of Pinzón Island. Galápagos, Ecuador.

Distribution of Pseudalsophis slevini Distribution of Pseudalsophis slevini in Pinzón Island

Etymology: The generic name Pseudalsophis, which comes from the Greek words pseudo (meaning “false”) and Alsophis (a genus of Caribbean snakes), refers to the similarity between snakes of the two genera.8 The specific epithet slevini honors Joseph Richard Slevin (1881–1957), an American scientist that worked as the curator of herpetology at the California Academy of Sciences (CAS) and was part of the research expedition conducted by this institution to the Galápagos Islands in 1905–1906. Slevin collected the holotype (the single specimen upon which the original description of the species was based) of the species.2 During the CAS expedition, nearly 4,000 reptiles were collected.9

See it in the wild: Pinzón Island is inaccessible to tourism. Researchers and members of the Galápagos National Park may visit the habitat of Pseudalsophis slevini, but only in the context of a scientific expedition or a conservation agenda.

Authors: Alejandro ArteagaaAffiliation: Khamai Foundation, Quito, Ecuador. and Juan M GuayasaminbAffiliation: Laboratorio de Biología Evolutiva, Universidad San Francisco de Quito (USFQ), Quito, Ecuador.,cAffiliation: Galapagos Science Center, Galápagos, Ecuador.,dAffiliation: Centro de Investigación de la Biodiversidad y Cambio Climático, Universidad Tecnológica Indoamérica, Quito, Ecuador.

Academic reviewers: Robert A Thomas and Luis Ortiz-Catedral.

Photographers: Jose VieiraaAffiliation: Tropical Herping (TH), Quito, Ecuador.,eAffiliation: ExSitu, Quito, Ecuador.

How to cite? Arteaga A, Guayasamin JM (2020) Pseudalsophis slevini. In: Arteaga A, Bustamante L, Vieira J (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from:

Literature cited:

  1. Field notes, Reptiles of Ecuador book project.
  2. Thomas RA (1997) Galápagos terrestrial snakes: biogeography and systematics. Herpetological Natural History 5: 19–40.
  3. Van Denburgh J (1912) Expedition of the California Academy of Sciences to the Galápagos Islands, 1905-1906. IV. The snakes of the Galápagos Islands. Proceedings of the California Academy of Sciences 1: 323–374.
  4. Ortiz-Catedral L, Christian E, Skirrow MJA, Rueda D, Sevilla C, Kumar K, Reyes EMR, Daltry JC (2019) Diet of six species of Galapagos terrestrial snakes (Pseudalsophis spp.) inferred from faecal samples. Herpetology Notes 12: 701–704.
  5. Wood GC (1939) Zoological results of the George Vanderbilt South Pacific Expedition of 1937. Part IV. Galápagos reptiles. Notulae Naturae 16: 1–2.
  6. IUCN (2001) IUCN Red List categories and criteria: Version 3.1. IUCN Species Survival Commission, Gland and Cambridge, 30 pp.
  7. Clark DA (1981) Foraging patterns of black rats across a desert-montane forest gradient in the Galápagos Islands. Biotropica 13: 182–194.
  8. Zaher H, Grazziotin FG, Cadle JE, Murphy RW, Moura-Leite JC, Bonatto SL (2009) Molecular phylogeny of advanced snakes (Serpentes, Caenophidia) with an emphasis on South American Xenodontines: a revised classification and descriptions of new taxa. Papéis Avulsos de Zoologia 49: 115–153.
  9. Van Denburgh J (1907) Expedition of the California Academy of Sciences to the Galápagos Islands, 1905-1906. I. Preliminary descriptions of four new races of gigantic land tortoises from the Galápagos Islands. Proceedings of the California Academy of Sciences 1: 1–6.