Reptilia · Squamata
Pseudalsophis occidentalisVan Denburgh, 1912
Fernandina Racer
Photograph by Charlotte Kirchner, CC BY, via iNaturalist
A day-active, meat-eating snake from the Neotropic region, reaching 129 cm nose to tail.
Also called Western Galápagos Racer.
Reptilia › Squamata › Colubridae › Pseudalsophis
- Grows to
- 1285mm
- greatest recorded
- Eats
- Carnivorous
- Active
- Diurnal
- Lives
- Saxicolous, terrestrial
Longer than 83% of all colubrid snakes anyone has measured.
The bar is the rank itself: its length is the share of the family this animal exceeds. The chart below is the family’s real spread, on a logarithmic scale because body length here runs from 98 to 3,800 mm. The solid rule is this animal. Every bar is a count of real species, and nothing on this figure is estimated.
What is known
26 sourced facts, each taken from a named scientific dataset. How to read these.
Cited from a dataset unless a row is marked otherwise.
Two of these figures disagree
Body mass (adult female, mean) is given as 129, and Body mass (greatest) as 123.3 — but an average female cannot outweigh the heaviest animal recorded. They come from different sources and both are shown exactly as those sources give them.
Standing in the world
- Still living
- Extant
- Conservation status
- Least Concern
- Status assessed · the year the Red List last looked
- 2014
- Population trend
- Stable
The animal itself
- Limbs
- None
- Fangs
- At the back of the mouth
Size
- Length snout to vent · greatest recorded
- 750mm2 ft 6 in
- Length nose to tail · greatest recorded
- 1285mm4 ft 3 in
- Body mass · greatestcomputeddisputed
- 123.3g4.3 oz
- Body mass · adult female, meanmeasureddisputed
- 129g4.6 oz
Thomas 1997, Artega et al. 2019 (males 128.5 cm, females 114.2mm), Ortiz-Catedral et al. 2021: 61 females (SVL range: 49.60 – 100 cm)
snakes only in this source
computed from length by a family-level allometric equation, not weighed
How it lives
- Diet
- Carnivorous
- Active
- Diurnal
- Where it lives
- Saxicolous, terrestrial
- Habitat
- Shrubland
- Biome
- Deserts & Xeric Shrublands
- Region
- Neotropic
- Mainland or island
- Found only on islands
- Highest it lives · above sea level
- 1200m
- Range size
- 2999km²
lizards, fish and carrion (Artega et al. 2019), "feeding predominantly on small vertebrates such as lava lizards (Microlophus spp.), geckos (Phyllodactylus spp.), marine iguana hatchlings (Amblyrhynchus cristatus) (Ortiz-Catedral et al., 2019), and even small coastal fishes" (Ortiz-Catedral et al. 2021), marine fish in tidal pools (Cisneros-Heredia and Reyes-Puig 2023)
Artega et al. 2019
on soil, rocks and grass (Artega et al. 2019)
IUCN (0 to 1200)
Naming and history
- Suborder
- Serpentes
- Infraorder
- Alethinophidia
- Subspecies
- No
- Described by
- Van Denburgh
- Moved to another genus · since it was first described
- Yes
- Described in
- 1912
- Type locality
- Ecuador
Keeping one
4 ft 3 in × 2 ft 1 in × 3 ft 2 in(129 × 64 × 96 cm)
Minimum length × width × height, for one animal. Bigger is always better.
The standard sizes snakes as a fraction of total length: 1 × 0.5 × 0.75.
Lives on rock, so stable hard surfaces and basking ledges suit it.
Mindestanforderungen an die Haltung von Reptilien (Sachverständigengutachten), German Federal Ministry for Nutrition, Agriculture and Forestry, Animal Welfare Division, 10 January 1997. The standard states these floor areas are recommendations rather than binding limits.
From this animal’s own total length of 4 ft 3 in (1285 mm), at 1 × 0.5 × 0.75 times it, following the German federal welfare standard — how this is worked out.
No preferred body temperature has been recorded for Fernandina Racer. Rather than repeat a number from a care sheet, this page leaves it out.
Feeding
A prey item should be between the same width as the widest part of the snake's body and about 1.5 times that width.
Widely used across snake husbandry references. An alternative formulation gives prey at 10-15% of the snake's body mass. This is established practice, not a measurement.
14kJ per day
Worked out for an animal of 123 g, the heaviest recorded for Fernandina Racer — so it is the top of the range, not a figure for a particular animal. Weigh yours and the number will be lower.
An upper estimate, not a feeding target, and not veterinary advice. The equation covers only what an animal burns staying alive, so a growing, gravid or recovering animal needs more — and it was measured on wild animals, which move far more than one in an enclosure. Body condition and a vet who knows the species are what a feeding decision should rest on. Where this comes from.
What nobody knows
These are not gaps in our research. No scientific dataset records them for this species — and saying so is information you cannot get from a reference that simply leaves a field out.
- — Length snout to vent · adult female mean
- — Length snout to vent · adult male mean
- — Length snout to vent · adult mean
- — Female length · mean, nose to tail
- — Length nose to tail · adult male mean
- — Length nose to tail · adult mean
- — Largest female · snout to vent
- — Largest male · snout to vent
- — Largest female · shell length
- — Largest male · shell length
- — Hatchling length · snout to vent
- — Hatchling length · nose to tail
- — Largest juvenile · snout to vent
- — Largest juvenile · shell length
- — Egg length
- — Egg width
- — Body mass · a typical adult
- — Body mass at hatching
- — Longest recorded life
- — Preferred body temperature · chosen in a laboratory gradient
- — Body temperature when active · measured in the wild
- — Eats arthropods
- — Eats vertebrates
- — Eats plant matter
- — How it hunts
- — Reproduction
- — How the young develop
- — Gestation or incubation
- — Average clutch
- — Smallest clutch recorded
- — Largest clutch recorded
- — Mean clutch · smallest reported
- — Mean clutch · largest reported
- — Clutches in a year
- — Clutches a year · fewest
- — Clutches a year · most
- — First breeds from · youngest recorded
- — First breeds by · oldest recorded
- — Hatchling length · smallest recorded
- — Hatchling length · largest recorded
- — Age at first breeding · female
- — Mature from · youngest recorded
- — Mature by · oldest recorded
- — Size at maturity · smallest recorded
- — Size at maturity · largest recorded
- — Venomous
- — Body temp in the wild · lowest mean recorded
- — Body temp in the wild · highest mean recorded
- — Colour on the back
- — Pattern on the back
- — Pupil
- — Sex decided by
- — Red List criteria
- — Active season · shortest recorded
- — Active season · longest recorded
- — Density · lowest recorded
- — Density · highest recorded
- — Home range · largest recorded
- — Active in
- — Lowest it lives · above sea level
Others in Colubridae
Take this data
Everything on this page is available as data under CC BY 4.0 — use it freely, credit it, no permission needed.
This species as JSON · the whole dataset
Cite this page
The Reptile & Amphibian Encyclopedia (2026). Pseudalsophis occidentalis. Retrieved 2026-09-08, from https://www.allanglescreatures.com/species/pseudalsophis-occidentalis
@misc{pseudalsophis_occidentalis_2026,
title = {Pseudalsophis occidentalis},
author = {{The Reptile & Amphibian Encyclopedia}},
year = {2026},
url = {https://www.allanglescreatures.com/species/pseudalsophis-occidentalis}
}Sources
- Meiri, S. (2024). SquamBase — a database of squamate (Reptilia: Squamata) traits. Global Ecology and Biogeography. Public domain (CC0).
- Catalogue of Life (dataset 3LR), used under CC BY.
- Oskyrko, O. et al. (2024). ReptTraits: a comprehensive dataset of ecological traits in reptiles. Scientific Data. Used under CC BY 4.0.