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Common Garter Snake
Reptiles · Snakes

Common Garter Snake

Thamnophis sirtalis

Active, diurnal, fish-loving small snakeBeginner

Lifespan
8-14 years
Size
18-51 in (varies)
Social needs
Best kept singly; prone to cannibalism at feeding time
Time
Medium - feed every 3-7 days
Cost
Low to Medium
Diet
Carnivore - fish, worms, rodents

Overview

What is this animal?

  • Common garter snakes are small, fast, diurnal snakes that are active and engaging to watch, unlike many shy nocturnal species.
  • They are widespread across North America and come in many regional colour forms.
  • They have a weak rear-fang saliva that is harmless to humans, and they are semi-aquatic, enjoying water.
  • Their daytime activity makes them appealing, though their varied diet and faster metabolism set them apart from rodent-only snakes.

Temperament

  • Garter snakes are alert, quick, and curious, often more nervous than rodent-eating colubrids.
  • Many musk readily when first handled but settle with regular gentle contact.
Show 3 more
  • Their daytime activity makes them rewarding to observe.
  • They rarely bite, and their mild rear-fang saliva is harmless to most people.
  • Handle gently and briefly at first, letting the snake move through your hands rather than restraining it tightly.

A good fit for

  • Keepers wanting an active daytime snake
  • Those who can provide a varied diet
  • Beginners happy with frequent feeding
  • People wanting a smaller, engaging species

Common mistakes to avoid

  • Goldfish and other thiaminase-rich fish cause thiamine deficiency
  • Faster metabolism needs frequent feeding
  • Can be musky and nervous when handled
  • Needs good ventilation and a clean water area

Enclosure

Minimum 8 sq ft of floor · 47 x 24 x 24 in

Usually kept alone. Best kept singly; prone to cannibalism at feeding time

  • A single adult needs at least 4 x 2 x 2 ft, with plenty of cover, climbing branches and a large water area, as they enjoy soaking and swimming.
  • Common garters are prone to cannibalism at feeding time, so one snake per enclosure is the safe default; anyone who does keep more should choose same-size adults, always feed them apart, and add at least 2.2 sq ft (about 18 x 18 in) of floor for every extra snake.
  • Use an absorbent substrate kept clean, since frequent meals mean frequent waste.
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  • Provide a basking spot of 82-86°F and a cooler side around 70-75°F, with low-level UVB beneficial for these diurnal baskers.
  • Keep humidity moderate and ensure good ventilation to prevent respiratory problems.

Check your enclosure

Supplies

Setup

  • Enclosure, sized for the adult snake
  • Heating and thermostat
  • Thermometers and hygrometer
  • Substrate, hides at both ends, water bowl

Ongoing

  • Frozen rodents in the right size for your snake
  • Freezer container or bin dedicated to feeder storage
  • Long blunt-tipped feeding tongs
  • Sealable bags or a thawing tub for warming prey
  • Heavy, tip-proof water bowl (big enough to soak in for most species; a small bowl on the cool side for rosy and sand boas, which are kept dry)
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  • Digital kitchen scale for tracking weight
  • Digital thermometer for checking prey temperature

Safe substrate: Cypress mulch · Aspen shavings · Topsoil and coco fibre mix

Work out the cost

Care routine

Daily

  • Check temperatures and humidity
  • Look the animal over
  • Spot-clean waste and uneaten food

Every few days

  • Fresh water bowlevery 3 days
  • Short handling sessionevery 3 days
  • Feed fish, earthworms or small mice (adults every 4-7 days, juveniles every 3-5)every 4 days
Show 8 more

Weekly

  • Check every latch and vent
  • Watch for a shed cycle

Every few weeks

  • Check for mitesevery 2 weeks
  • Weigh-inevery 2 weeks

Monthly

  • Deep-clean decor, glass and bowls
  • Test thermostats, lamps and guards

Less often

  • Refresh the substrateevery 3 months
  • Check the UVB lamp's age and replace it if due (if one is fitted)every 6 months

Vet: Annual exam and faecal check, every 12 months

Tools

Is your enclosure big enough?Check your measurements against the recommended sizeWhat will it cost?Setup, monthly and over its whole life, itemisedCan it eat that?Search 20 foods, from everyday to never

Care in depth

Diet

Carnivore - fish, worms, rodents
  • Garter snakes have a varied carnivorous diet of fish, earthworms, and rodents.
  • Do not feed goldfish or rosy red minnows: they contain thiaminase, which destroys vitamin B1 and causes a neurological deficiency.
  • Use thiaminase-free fish such as guppies or platies instead, and offer earthworms (never red wigglers) and whole rodent prey for balance; a thiamine supplement is a sensible safeguard for a snake that eats a lot of fish.
  • Their fast metabolism means feeding juveniles every 3-5 days and adults every 4-7 days, with worm- and fish-fed snakes at the shorter end and rodent-fed snakes at the longer.
  • A varied diet is essential to long-term health and prevents nutritional deficiencies.

Health

Signs of good health, and the common problems
  • Garter snakes are prone to vitamin and thiamine deficiencies from poor diets, and to respiratory infections in damp, poorly ventilated setups.
  • Frequent feeding makes a clean enclosure especially important to prevent bacterial problems.
  • Feed a varied, balanced diet and supplement where needed.
  • Maintain good hygiene and ventilation.
  • Their shorter lifespan and faster metabolism call for attentive feeding and prompt veterinary care for any lethargy or breathing changes.

Is this urgent?

5 warning signs and how fast to act, 2 of them right away

Most snake worry is about feeding, and most feeding worry is misplaced. Check the guide for this species' normal fast before treating a refusal as illness.

Go now

Open-mouth breathing, bubbles at the nostrils, or an audible whistleGo now. Respiratory infection. Most snakes have only one working lung, and even boas and pythons, whose second lung is much smaller, have little reserve.
Now
Cannot right itself, or holds the head and neck in an unnatural twist (a western hognose that rolls over and plays dead when disturbed, then recovers once left alone, is showing normal defensive behaviour)Go now. Neurological signs are always urgent in a snake.
Now

Today

Retained eyecaps after a shed, or a ring of stuck shed on the tail tipRaise humidity and provide a damp hide. Call if it is not resolved within a day. Almost always humidity that was too low during the blue phase. A constricting ring costs the tail tip.
Today

Soon

A regurgitated mealDo not offer food again for at least a fortnight. Check the warm-end temperature today, then call if it happens twice. Usually too cold, handled too soon, or a meal too large. Repeated regurgitation is a different and more serious problem.
Check today
Refusing food for longer than is normal for this speciesLog the refusal and check the species guide. For an adult ball python, a fast of about a month is not in itself a cause for concern, and much longer voluntary fasts are documented. Weigh weekly through it. The weight trend, not the calendar, is what tells you whether a fast matters.
Log it first

This is general guidance for a healthy adult, not a diagnosis. An exotics vet who knows your animal always overrides it, and the time to find one is before you need one.

Bedding and substrate

5 safe, 1 with a caveat, 2 to avoid

For snakes the substrate has to hold the right humidity for the shed, and let the animal get fully under it.

Safe

Cypress mulchHolds humidity without going sour quickly. A common default for tropical snakes.
safe
Aspen shavingsThe classic for colubrids. Excellent for burrowing; replace any patch that gets wet.
safe
Topsoil and coco fibre mixBioactive-ready and holds a burrow.
safe
Sand-topsoil mixFor arid and sandy-soil burrowers such as hognoses: plain topsoil with some play sand mixed in holds a burrow. Keep it dry.
safe
Paper towel or newspaperQuarantine, feeding response problems, and post-surgery.
safe

With a caveat

Aspen in a high-humidity setupIt moulds. Aspen suits dry-side species; wet species need mulch or soil.
with a caveat

Never

Pine and cedarThe same aromatic oils that make them unsafe in small-mammal bedding.
never
Pure loose sand for species from humid habitatsIt holds little moisture, which makes shed problems more likely, and it does not hold a burrow. A soil mix with some sand is fine for snakes from sandy, dry habitats such as hognoses and sand and rosy boas.
never

Stuck shed and retained eyecaps are usually a humidity failure during the blue phase, not a substrate failure afterwards.

Top resources for more info

Independent creators and organisations we would send a friend to. We have no affiliation with any of them, and nothing here is sponsored. Links checked 2026-10-22.

YouTubers

Snake DiscoverySnake care and behaviour explained (run by a reptile shop)Lori TorriniSnake behaviour, enrichment and choice-based handlingReptiles and ResearchEvidence-led husbandry: enclosure size, UVB, thermal gradients, enrichment

Sites

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Is your enclosure big enough?

These are the smallest sizes that give good conditions, not legal minimums. More room is always better.

Minimum 8 sq ft of floor · 47 x 24 x 24 in

Every figure, and where it comes from

A common garter over 47 in, which a few reach, needs an enclosure at least as long as itself and half as wide.

Minimum floor area8 sq ft of continuous, unbroken floor
As dimensions47 x 24 x 24 in
CompanyUsually kept alone. Best kept singly; prone to cannibalism at feeding time
The recognised standards do not agree on this one
ReptiFiles: 4 x 2 x 2 ft for one average adult. The figure this site uses: ReptiFiles' size for one average garter snake and the size of all its recommended garter snake enclosures for snakes of 3-4 ft, with larger always strongly recommended. Common garters run 20-51 in. Checked 2026-10-23.
Austrian legal minimum (2. Tierhaltungsverordnung, Anlage 3): 5.5 sq ft of floor and 16 in of height for one or two adults, plus 2.2 sq ft for each extra snake (Thamnophis sirtalis sirtalis). A legal minimum, recorded for context. Less than the figure used here. Checked 2026-10-23.

What it really costs

Setup, monthly, first year and across a whole life, itemised and with the electricity worked out from the actual wattage. Published figures for the same animal disagree by a factor of four, so the calculator shows ranges rather than picking one.

Can a Common Garter Snake eat that?

Garter snakes are the exception among pet snakes: fish and earthworms as well as small rodents, fed more often than a rodent-eating snake.

The full list: 20 foods

Never (17)

AlcoholNo safe amount at any body weight on this site.
never
AvocadoPersin, concentrated in the leaves, skin and stone. It damages the heart in birds and in many mammals, rabbits and rodents among them; it has not been studied in reptiles, so treat it as unsafe for them too.
never
CaffeineCoffee, tea and energy drinks. Cardiac and neurological toxicity at tiny doses for an animal this size.
never
ChocolateTheobromine and caffeine. Small mammals and reptiles cannot clear either.
never
Cooked, seasoned or processed meatNot whole prey: muscle meat lacks the bone and organs that make a rodent a complete food, and salt and seasoning do harm.
never
Fish caught from the wildParasites and pollutants. Separately, thiaminase depends on the fish species, not where it was caught: goldfish, carp, many minnows and smelt carry it even when shop-bought, and cause vitamin B1 deficiency if fed regularly.
never
GarlicSame allium toxicity as onion, and more concentrated by weight.
never
Goldfish and rosy red minnowsThiaminase destroys vitamin B1 and causes a neurological deficiency.
never
Greens, vegetables and fruitSnakes are obligate carnivores.
never
Insect feedersNot part of a snake's diet, and loose crickets chew on resting or shedding snakes.
never
LeekAllium family. Same mechanism as onion and garlic.
never
Live rodentsA live rodent can bite and seriously injure a snake. Frozen-thawed only.
never
OnionOrganosulphur compounds damage red blood cells. The whole allium family is out.
never
Red wigglersSpecialist garter care guides say never to use them as feeders.
never
RhubarbVery high in soluble oxalate, high enough to cause acute kidney injury. The leaves are worse than the stalks.
never
Salty or seasoned human foodSalt, oil and seasoning. Crisps, chips, seasoned leftovers and processed meat are all out.
never
Wild-caught preyParasites and rodenticide.
never

Everyday foods (3)

EarthwormsA natural garter food. Chop them to about the size of the snake's head and offer several at a time. Sources differ on nightcrawlers: ReptiFiles advises avoiding them. Several per feed.
everyday food
Frozen-thawed rodentsSmall mice, pinkies or fuzzies sized to the snake's girth; many garters take them more readily scented with fish. They balance a fish-and-worm diet and are fed least often of the three. One prey item per feed, at the interval in the species guide.
everyday food
Low-thiaminase fish (guppies, platies)Part of a varied diet, not the whole of it. Several small fish per feed, alongside worms and rodents.
everyday food

That food is not on our list. A snake eats whole prey and nothing else, so if it is not a correctly sized prey item from the species guide, leave it out.

Fish and worms are not complete the way whole rodents are: every so often, lightly dust them with a calcium and multivitamin mix.