Reptilia · Squamata
Thamnophis brachystomaCope, 1892
Shorthead Garter Snake
Photograph by feline, CC BY, via iNaturalist
A day-active, meat-eating snake from the Nearctic region, reaching 559 mm nose to tail.
Reptilia › Squamata › Colubridae › Thamnophis
- Grows to
- 559mm
- greatest recorded
- Eats
- Carnivorous
- Active
- Diurnal
- Lives
- Semi-aquatic
Longer than only 39% 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
38 sourced facts, each taken from a named scientific dataset. How to read these.
Cited from a dataset unless a row is marked otherwise.
Standing in the world
- Still living
- Extant
- Conservation status
- Least Concern
- Status assessed · the year the Red List last looked
- 2007
- Population trend
- Stable
The animal itself
- Limbs
- None
- Pupil
- Round
- Venomous
- Yes
- Fangs
- At the back of the mouth
- Body temperature when active · measured in the wild
- 15.24°C59 °F
- Body temp in the wild · mean, when active
- 9–35°C48–95 °F
mean body temperature of active individuals in nature
body temperature of active animals in nature
Size
- Length nose to tail · greatest recorded
- 559mm22 in
- Hatchling length · snout to vent
- 99.75mm4 in
- Body mass · greatestcomputed
- 42.87g1.5 oz
- Body mass at hatchingmeasured
- 0.41g0.01 oz
snakes only in this source
559 mm total length (Feldman et al. 2016), Rossman et al. 1996 (neonate SVL 99.1-100.4 mm, yes same as atratus)
computed from length by a family-level allometric equation, not weighed
How it lives
- Diet
- Carnivorous
- Active
- Diurnal
- Where it lives
- Semi-aquatic
- Habitat
- Forest, Grassland
- Biome
- Temperate Broadleaf & Mixed Forests
- Region
- Nearctic
- Mainland or island
- Mainland
- Highest it lives · above sea level
- 1626m
- Range size
- 21,532km²
- Density
- 20per hectare
vermivore (Deepak et al. 2022)
Feldman 2015
Aquatic (Feldman 2015)/Terrestrial (Deepak et al. 2022)
Breeding
- Reproduction
- Viviparous
- Average clutch
- 16eggs
- Eggs or young per clutch
- 7–16eggs
- Mean clutch
- 7.2–16eggs
- Clutches in a year
- 1per year
- Clutches a year
- 0.75per year
- First breeds at
- 24months
Feldman et al. 2015, Meiri et al. 2019
mean 16 (Meiri et al. 2019), means 7.2-7.6 (Rossman et al. 1996)
Naming and history
- Suborder
- Serpentes
- Infraorder
- Alethinophidia
- Subspecies
- No
- Described by
- Cope
- Moved to another genus · since it was first described
- Yes
- Described in
- 1892
- Type locality
- USA
Keeping one
22 in × 11 in × 16.5 in(56 × 28 × 42 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.
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 22 in (559 mm), at 1 × 0.5 × 0.75 times it, following the German federal welfare standard — how this is worked out.
Active animals measured in the wild averaged 59 °F (15.2 °C).
Mean body temperature of active individuals measured in nature. A measurement of the animal, not a setting for a thermostat.
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.
6kJ per day
Worked out for an animal of 43 g, the heaviest recorded for Shorthead Garter Snake — 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 · greatest recorded
- — 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 · nose to tail
- — Largest juvenile · snout to vent
- — Largest juvenile · shell length
- — Egg length
- — Egg width
- — Body mass · a typical adult
- — Body mass · adult female, mean
- — Longest recorded life
- — Preferred body temperature · chosen in a laboratory gradient
- — Eats arthropods
- — Eats vertebrates
- — Eats plant matter
- — How it hunts
- — How the young develop
- — Gestation or incubation
- — 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
- — Colour on the back
- — Pattern on the back
- — Sex decided by
- — Red List criteria
- — Active season · shortest recorded
- — Active season · longest 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). Thamnophis brachystoma. Retrieved 2026-09-08, from https://www.allanglescreatures.com/species/thamnophis-brachystoma
@misc{thamnophis_brachystoma_2026,
title = {Thamnophis brachystoma},
author = {{The Reptile & Amphibian Encyclopedia}},
year = {2026},
url = {https://www.allanglescreatures.com/species/thamnophis-brachystoma}
}Sources
- Meiri, S. (2024). SquamBase — a database of squamate (Reptilia: Squamata) traits. Global Ecology and Biogeography. Public domain (CC0).
- Oskyrko, O. et al. (2024). ReptTraits: a comprehensive dataset of ecological traits in reptiles. Scientific Data. Used under CC BY 4.0.
- Catalogue of Life (dataset 3LR), used under CC BY.