Eastern Galápagos Racer

Reptiles of Ecuador | Serpentes | Colubridae | Pseudalsophis | Pseudalsophis biserialis

English common names: Eastern Galápagos Racer, San Cristóbal Racer, Floreana Racer.

Spanish common names: Culebra oriental de Galápagos, serpiente corredora de Galápagos.

Recognition: ♂♂ 80.5 cm ♀♀ 81 cm. Pseudalsophis biserialis is the only snake known to occur on San Cristóbal Island and three of the surrounding islets of Floreana Island. The snakes on San Cristóbal Island are usually striped, whereas those near Floreana are mostly spotted.

Natural history: Uncommon on San Cristóbal Island, but frequent on the islets near Floreana Island. Pseudalsophis biserialis is a diurnal and terrestrial snake inhabiting volcanic rock areas, dry shrublands, dry grasslands, and deciduous forests.1,2 During the daytime, especially around 8:00 and 17:00, Eastern Galápagos Racers are active on soil, leaf litter, and rocks.1,3 Individuals of P. biserialis are mildly venomous, which means they are dangerous to small prey, but not to humans.4 They are foraging predators that feed on geckos (Phyllodactylus baurii and P. leei), lizards (Microlophus bivittatus and M. grayii), juvenile Marine Iguanas (Amblyrhynchus cristatus), invertebrates, and possibly birds.1,3,5 Juveniles of Pseudalsophis biserialis are preyed upon by centipedes.3

Conservation: Near Threatened.2 Pseudalsophis biserialis is listed in this category because this species is tolerant of habitat modification, has presumed stable populations, and is not undergoing a continuing decline in the extent and quality of its habitat.2 However, the species has already been extirpated from one island: Floreana.3 Currently, the Eastern Galápagos Racer persists on three small islets around Floreana and on San Cristóbal Island. Confirmed ongoing threats for P. biserialis include predation by housecats and chickens.3,6

Special thanks to Luis Ortiz-Catedral, our official protector of the Eastern Galápagos Racer, for symbolically adopting this species and helping bring the Reptiles of Galápagos project to life.

Distribution: Eastern Galápagos Racers persist on an estimated 448 km2 area in San Cristóbal Island and three of the surrounding islets of Floreana Island (Champion, Enderby, and Gardner), but they have been extirpated from Floreana. Galápagos, Ecuador.

Distribution of Pseudalsophis biserialis Distribution of Pseudalsophis biserialis in and around Floreana Island Distribution of Pseudalsophis biserialis in San Cristóbal 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.7 The specific epithet biserialis, which comes from the Latin words bis (meaning “double”), series (meaning “row”), and -alis (meaning “pertaining to”),8 probably refers to the two rows of spots present on the dorsum of some individuals of this species.

See it in the wild: Pseudalsophis biserialis is not a common species, but, with luck, it can be seen with ~10% certainty at some tourism sites on San Cristóbal Island. The easiest place to see the Eastern Galápagos Racer is along the trails leading from Puerto Baquerizo Moreno to Playa Carola. The best time to look for, and photograph, Eastern Galápagos Racers is during the first hours after sunrise or right before sunset.

Authors: Alejandro Arteaga,aAffiliation: Tropical Herping (TH), Quito, Ecuador. Gabriela Aguiar, 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. and Alejandro ArteagaaAffiliation: Tropical Herping (TH), Quito, Ecuador.

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

Literature cited:

  1. Field notes, Reptiles of Ecuador book project.
  2. Márquez C, Cisneros-Heredia DF, Yánez-Muñoz M (2017) Pseudalsophis biserialis. The IUCN red list of threatened species. Available from: www.iucnredlist.org
  3. Christian EJ (2017) Demography and conservation of the Floreana racer (Pseudalsophis biserialis biserialis) on Gardner-by-Floreana and Champion islets, Galápagos Islands, Ecuador. PhD thesis, Auckland, New Zealand, Massey University.
  4. Thomas RA (1997) Galápagos terrestrial snakes: biogeography and systematics. Herpetological Natural History 5: 19–40.
  5. Washington Tapia, unpublished data.
  6. Torres ML, Mena CF (2018) Understanding invasive species in the Galápagos Islands: from the molecular to the landscape. Springer, New York, 237 pp.
  7. 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.
  8. Brown RW (1956) Composition of scientific words. Smithsonian Books, Washington, 882 pp.