Published October 10, 2019. Updated May 25, 2024. Open access. Peer-reviewed.

Darwin’s Racer (Pseudalsophis darwini)

Reptiles of Ecuador | Serpentes | Colubridae | Pseudalsophis darwini

English common name: Darwin’s Racer.

Spanish common name: Culebra de Darwin.

Recognition: ♂♂ 51 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=35.7 cm. ♀♀ 54.3 cmMaximum distance from the snout to the tip of the tail. Snout–vent length=38.3 cm..¹ Pseudalsophis darwini is one of two snake species known to occur on Isabela Island, Fernandina Island, and Tortuga Islet.^1,2 It is characterized by having a black dorsum with a series of paired pale goldenrod yellow bars and a light brown head cap (Fig. 1).^1,2 This pattern differentiates it from the striped or spotted P. occidentalis, a larger co-occurring snake.³

Figure showing an adult male of Pseudalsophis darwini

Figure 1: Adult male of Pseudalsophis darwini from Punta Espinoza, Fernandina Island, Galápagos, Ecuador.

Natural history: Pseudalsophis darwini is a diurnal snake that inhabits coastal volcanic rock areas, dry grasslands, and seasonally dry forests.^1,2,4 During the daytime, these snakes are typically seen swiftly moving on soil and rocks.² When not active, they have been found hidden under lava blocks, under tree bark, or beneath wooden boardwalks.⁵

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Conservation: Least Concern Believed to be safe from extinction given current circumstances.. Pseudalsophis darwini is a recently described species.¹ Therefore, it has not been formally evaluated by the IUCN Red List. Here, it is provisionally assigned to the LC category because the 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 in Galápagos 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 population of P. darwini.²

Distribution: Pseudalsophis darwini is endemic to Isabela Island, Fernandina Island, and Tortuga Islet in Galápagos, Ecuador (Fig. 2).

Figure 2: Distribution of Pseudalsophis darwini in Galápagos. The star corresponds to the type locality: Tortuga Islet. See Appendix 1 for a complete list of the presence localities included in the map.

Etymology: The generic name Pseudalsophis comes from the Greek words pseudo (=false) and Alsophis (a genus of Caribbean snakes), referring to the similarity between snakes of the two genera.¹ The specific epithet darwini honors Charles Darwin.¹

See it in the wild: Darwin’s Racers can be seen at a rate of about once every few days at Punta Espinoza in Fernandina Island. The best time to look for them is during the first hours after sunrise or right before sunset.

Special thanks to David Salazar-Valenzuela for symbolically adopting the Darwin’s Racer and helping bring the Reptiles of Ecuador book project to life.

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Authors: Alejandro Arteaga^aAffiliation: Khamai Foundation, Quito, Ecuador. and Juan M Guayasamin^bAffiliation: Universidad San Francisco de Quito, Quito, Ecuador.

Academic reviewers: Robert A Thomas^cAffiliation: Loyola University, New Orleans, United States. and Luis Ortiz-Catedral^dAffiliation: Massey University, Palmerston North, New Zealand.

Photographer: Jose Vieira^eAffiliation: Tropical Herping (TH), Quito, Ecuador.^,^fAffiliation: ExSitu, Quito, Ecuador.

How to cite? Arteaga A, Guayasamin JM (2024) Darwin’s Racer (Pseudalsophis darwini). 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/WDKL3175

Literature cited:

Zaher H, Yánez-Muñoz MH, Rodrigues MT, Graboski R, Machado FA, Altamirano-Benavides M, Bonatto SL, Grazziotin FG (2018) Origin and hidden diversity within the poorly known Galápagos snake radiation (Serpentes: Dipsadidae). Systematics and Biodiversity 16: 614–642. DOI: 10.1080/14772000.2018.1478910
Arteaga A, Bustamante L, Vieira J, Tapia W, Guayasamin JM (2019) Reptiles of the Galápagos: life on the Enchanted Islands. Tropical Herping, Quito, 208 pp. DOI: 10.47051/AQJU7348
Thomas RA (1997) Galápagos terrestrial snakes: biogeography and systematics. Herpetological Natural History 5: 19–40.
Cisneros-Heredia DF, Reyes-Puig C (2023) Natural history and conservation of the Galápagos snake radiation. In: Lillywhite HB, Martins M (Eds) Islands and snakes. Oxford University Press, 158–182. DOI: 10.1093/oso/9780197641521.003.0009
Field notes, Reptiles of Ecuador book project.

Appendix 1: Locality data used to create the distribution map of Pseudalsophis darwini in Ecuador (Fig. 2). Go to the section on symbols and abbreviations for a list of acronyms used. Asterisk (*) indicates type locality.

Country	Province	Locality	Source
Ecuador	Galápagos	Cabo Barrington	Cisneros-Heredia & Reyes-Puig 2023
Ecuador	Galápagos	Cabo Douglas	Arteaga et al. 2019
Ecuador	Galápagos	Cabo Douglas, 4 km SE of	Cisneros-Heredia & Reyes-Puig 2023
Ecuador	Galápagos	Cartago Bay	Thomas 1997
Ecuador	Galápagos	Centro de Crianza Arnaldo Tupiza	iNaturalist; photo examined
Ecuador	Galápagos	Cerro Azul, western foothills	iNaturalist; photo examined
Ecuador	Galápagos	Volcán Alcedo (Cowley Mountain), eastern slope	Fritts and Fritts 1982; Thomas 1997
Ecuador	Galápagos	Piedras Blancas	Zaher et al. 2018
Ecuador	Galápagos	Puerto Villamil	Zaher et al. 2018
Ecuador	Galápagos	Puerto Villamil, 16 km NE of	iNaturalist; photo examined
Ecuador	Galápagos	Punta Espinosa	Arteaga et al. 2019
Ecuador	Galápagos	Punta Espinoza, 4 km S of	iNaturalist; photo examined
Ecuador	Galápagos	Punta Moreno	Arteaga et al. 2019
Ecuador	Galápagos	Tagus Cove, 3 km N of	iNaturalist; photo examined
Ecuador	Galápagos	Tortuga islet (Brattle)*	Zaher et al. 2018
Ecuador	Galápagos	Villamil, 4 km E of	iNaturalist; photo examined