Darwin's Racer

Reptiles of Ecuador | Serpentes | Colubridae | Pseudalsophis | Pseudalsophis darwini

Spanish common names: Culebra de Darwin, serpiente corredora de Darwin.

Recognition: ♂♂ 51 cm ♀♀ 54.3 cm. Pseudalsophis darwini is one of two snake species occurring on Isabela Island, Fernandina Island, and Tortuga Islet. The other species is the Western Galápagos Racer (P. occidentalis), a larger snake that does not have a pattern of transverse black bands throughout the body.

Natural history: Uncommon to locally frequent. Pseudalsophis darwini is a diurnal snake inhabiting volcanic rock areas, dry grasslands, and deciduous forests.1 During daytime, this mildly venomous (dangerous to small prey, not to humans)2 foraging predator is active on soil and rocks.1


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Conservation: Least Concern. We consider Pseudalsophis darwini to be in this category following IUCN criteria3 because this species is widespread in western Galápagos and is, presumably, not undergoing population declines nor facing major immediate threats of extinction. Fernandina is one of the most pristine islands of the Galápagos Archipelago and is currently free of exotic predators that may prey upon snakes. The threats that Darwin's Racers face in Fernandina are volcanic eruptions and the potential for the introduction of aggressive exotic species, mainly rats and cats. In Isabela, the largest island of the Archipelago, conservation challenges are more complex since the island has several introduced species, including humans, that may have an impact on the P. darwini population.

Special thanks to David Salazar-Valenzuela and Eric Osterman, our two official protectors of the Darwin's Racer, for symbolically adopting this species and helping bring the Reptiles of Galápagos project to life.

Distribution: Pseudalsophis darwini is endemic to Isabela Island, Fernandina Island, and Tortuga Islet, which collectively account for an area of 5,313 km2, although Darwin's Racers probably occur on a much smaller area. Galápagos, Ecuador.

Distribution of Pseudalsophis darwini Distribution of Pseudalsophis darwini in western Galápagos

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.4 The specific epithet darwini honors Charles Darwin.5

See it in the wild: Darwin's Racers can be seen with ~10% certainty in Punta Espinoza in Fernandina Island. The best time to look for them is during the first hours after sunrise or right before sunset.

Authors: Alejandro ArteagaaAffiliation: Tropical Herping (TH), 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 darwini. In: Arteaga A, Bustamante L, Vieira J, Guayasamin JM (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: www.tropicalherping.com

Philadelphia Zoo logoThis species account of the Darwin's Racer (Pseudalsophis darwini) is available for free online thanks to the support of Philadelphia Zoo.

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Literature cited:

  1. Tropical Herping field notes.
  2. Thomas RA (1997) Galápagos terrestrial snakes: biogeography and systematics. Herpetological Natural History 5: 19–40.
  3. IUCN (2001) IUCN Red List categories and criteria: Version 3.1. IUCN Species Survival Commission, Gland and Cambridge, 30 pp.
  4. 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.
  5. Zaher H, Yánez-Muñoz MH, Rodrigues MT, Graboski R, Machado FA, Altamirano-Benavides M, Bonatto SL, Grazziotin F (2018) Origin and hidden diversity within the poorly known Galápagos snake radiation (Serpentes: Dipsadidae). Systematics and Biodiversity 16: 614–642.