Reptilia · Squamata
Thamnophis gigasFitch, 1940
Giant Garter Snake
Photograph by Ken-ichi Ueda, CC BY, via iNaturalist
A water-living, day-active, meat-eating snake from the Nearctic region, reaching 165 cm nose to tail.
Reptilia › Squamata › Colubridae › Thamnophis
- Grows to
- 1650mm
- greatest recorded
- Eats
- Carnivorous
- Active
- Diurnal
- Lives up to
- 11.75years
Longer than 91% 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
40 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
- Vulnerable
- Status assessed · the year the Red List last looked
- 2007
- Population trend
- Decreasing
- Red List criteria
- B1ab(ii,iii,iv,v)
The animal itself
- Limbs
- None
- Pupil
- Round
- Venomous
- Yes
- Fangs
- At the back of the mouth
- Longest recorded life
- 11.75years
- Preferred body temperature · chosen in a laboratory gradientmeasured
- 27.5°C
- Body temperature when active · measured in the wild
- 21.54°C71 °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 snout to vent · greatest recorded
- 1040mm3 ft 5 in
- Length snout to vent · adult female mean
- 790mm2 ft 7 in
- Length nose to tail · greatest recorded
- 1650mm5 ft 5 in
- Hatchling length · snout to vent
- 197.1mm7.75 in
- Body mass · greatestcomputed
- 556.7g1.2 lb
- Body mass at hatchingmeasured
- 4.65g0.16 oz
1650 mm total length (Feldman et al. 2016), Rose et al. 2018 (104 females, mean SVL 790±88.6 mm, range 514–1040, mass 317±114.3 g, range 99–815 g, almost sure it is pre-partum; 154 neonates SVL 187.7±110.1 mm, range 146–207 mm, mass 4.3±1 g, range 2–7.3), Rossman et al. 1996 (neonates 206.4 mm SVL)
snakes only in this source
computed from length by a family-level allometric equation, not weighed
How it lives
- Dietcomputed
- Carnivorous
- Active
- Diurnal
- Where it lives
- Aquatic
- Habitat
- Wetlands
- Biome
- Temperate Grasslands, Savannas & Shrublands
- Region
- Nearctic
- Mainland or island
- Mainland
- Highest it lives · above sea level
- 130m
- Range size
- 14,045km²
no actual data but can be imputed as carnivorous like all snakes
Feldman 2015
O'Shea 2018, Deepak et al. 2022
0-122 (O'Shea 2018)
Breeding
- Reproduction
- Viviparous
- Average clutch
- 11.5eggs
- Eggs or young per clutch
- 5–35eggs
- Mean clutch
- 15.5–23.1eggs
- Clutches a year
- 0.47–0.64per year
Feldman et al. 2015
max=24 (O'Shea 2018), mean=23.1 (Feldman 2015, Rossman et al. 1996), 5-35, mean 15.5-15.9 but usually some dead neonates (Rose et al. 2018)
Naming and history
- Suborder
- Serpentes
- Infraorder
- Alethinophidia
- Subspecies
- No
- Described by
- Fitch
- Moved to another genus · since it was first described
- No
- Described in
- 1940
- Type locality
- USA
Keeping one
Giant Garter Snake is assessed as Vulnerable on the IUCN Red List. Species at risk in the wild are often covered by CITES and by national law, which decide what may be bought, sold, moved across a border or kept at all — and captive-bred and wild-caught animals are usually treated differently. Check the rules where you are before acquiring one. Nothing below is a judgement about keeping this species; it is what a published welfare standard says about space, and what the animal itself was measured doing.
5 ft 5 in × 2 ft 8 in × 4 ft 1 in(165 × 83 × 124 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.
Spends time in water, so a water area is part of the enclosure rather than a dish.
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 5 ft 5 in (1650 mm), at 1 × 0.5 × 0.75 times it, following the German federal welfare standard — how this is worked out.
In a laboratory thermal gradient this species settled at 82 °F (27.5 °C).
Preferred body temperature, recorded in a laboratory gradient where the animal could choose freely. 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.
54kJ per day
Worked out for an animal of 557 g, the heaviest recorded for Giant 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 · 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
- — Eats arthropods
- — Eats vertebrates
- — Eats plant matter
- — How it hunts
- — How the young develop
- — Gestation or incubation
- — Clutches in a year
- — 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
- — Colour on the back
- — Pattern on the back
- — Sex decided by
- — 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). Thamnophis gigas. Retrieved 2026-09-08, from https://www.allanglescreatures.com/species/thamnophis-gigas
@misc{thamnophis_gigas_2026,
title = {Thamnophis gigas},
author = {{The Reptile & Amphibian Encyclopedia}},
year = {2026},
url = {https://www.allanglescreatures.com/species/thamnophis-gigas}
}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.