California Red-Sided Garter Snake (Thamnophis sirtalis infernalis) Care Sheet
The California Red-Sided Garter Snake (Thamnophis sirtalis infernalis) is one of the most striking members of the common garter snake complex.
It is native to coastal and parts of central California and is immediately recognisable by its intense red or orange side markings, contrasting dark body colour and pale dorsal stripe.
Although closely related to other forms of Thamnophis sirtalis, the California Red-Sided Garter Snake should be maintained and recorded as a distinct geographical form. Locality information is particularly important where animals are maintained for breeding.
These snakes are active, alert, semi-aquatic and primarily diurnal. They make excellent display animals when given sufficient space, clean water, abundant cover, appropriate basking opportunities and a nutritionally varied diet.
They are fast, can musk when stressed and should not be underestimated simply because of their slender build.
Quick Facts
Scientific name: Thamnophis sirtalis infernalis
Common name: California Red-Sided Garter Snake
Family: Colubridae
Native range: California, USA
Lifestyle: Terrestrial / semi-aquatic
Activity: Primarily diurnal
Adult length: Commonly approximately 24–36 inches; large females may exceed this
Lifespan: Approximately 8–12+ years, with longer lifespans possible under excellent care
Experience level: Beginner to intermediate
Diet: Varied whole-prey diet including rodents, earthworms, amphibian-type prey and suitable fish
Temperament: Alert, fast and generally manageable when captive-bred
Adult enclosure: Approximately 36" × 18" × 18" minimum for a typical adult; 48" × 24" × 18–24" preferable for large females
Basking area: Approximately 28–30°C
Warm area: Approximately 24–27°C
Cool area: Approximately 19–23°C
Night temperature: Approximately 16–20°C
Humidity: Generally around 40–60%, with access to a more humid retreat
UVB: Low-level UVB recommended
Venom: Rear-fanged with venom of very low medical significance to humans
Handling: Usually manageable but extremely quick
Social housing: Individual housing recommended; carefully managed group housing is possible for compatible animals
Natural Distribution
The California Red-Sided Garter Snake occurs naturally in California.
Its distribution is concentrated particularly in coastal and nearby regions.
It is associated with habitats containing reliable access to water and dense vegetation.
Because this is a geographically distinct form, animals of known provenance should have locality information retained.
Natural Habitat
Typical habitats include:
- marshes
- ponds
- streams
- wet meadows
- riparian vegetation
- grassland near water
- coastal habitats
- agricultural waterways
They are highly capable swimmers but spend substantial time on land.
Appearance
This is one of the most colourful garter snakes.
Typical individuals show:
- black or very dark body colour
- vivid red or orange lateral markings
- pale yellow, cream or bluish dorsal stripe
- contrasting checkering or spotting
Colour intensity varies among individuals.
Well-coloured adults can be exceptionally striking.
Adult Size
Adults commonly reach approximately:
24–36 inches
Large females may exceed this.
Females are generally:
- longer
- heavier
- more robust
than males.
Behaviour
California Red-Sided Garter Snakes are very active.
Typical behaviour includes:
- basking
- swimming
- exploring
- hunting
- moving through vegetation
- investigating hides
- following scent trails
A healthy animal may make extensive use of the enclosure throughout the day.
Diurnal Activity
These snakes are primarily active during daylight.
They benefit from:
- good daytime lighting
- low-level UVB
- a visible basking area
- naturalistic cover
This makes them excellent observation animals.
Temperament
Captive-bred animals often become manageable with time.
Juveniles may be:
- nervous
- extremely fast
- defensive
- prone to musking
Most become calmer as they mature.
Musking
A frightened garter snake may release strong-smelling cloacal secretions.
This is a normal defensive response.
Frequent musking during handling usually indicates that the animal is stressed.
Biting
Garter snakes may bite defensively or during feeding.
They possess enlarged rear teeth and a mild venom system primarily adapted to prey.
Human bites are generally minor.
Prolonged chewing bites should still be avoided.
Enclosure Size
For a typical adult:
36" × 18" × 18"
should be considered a practical minimum.
Large females benefit substantially from:
48" × 24" × 18–24"
or larger.
Additional floor space is particularly valuable because garter snakes are highly active.
Enclosure Security
These snakes are exceptional escape artists.
Check carefully around:
- sliding-door gaps
- ventilation openings
- cable ports
- lids
- corners
- door tracks
Juveniles can escape through extremely small openings.
Enclosure Furnishings
Provide:
- multiple hides
- cork bark
- vegetation
- leaf litter
- low branches
- basking areas
- water
- open movement space
The enclosure should contain both dense cover and more open areas.
Hides
At minimum include:
- warm hide
- cool hide
- humid hide
Additional cover should be available throughout the enclosure.
Substrate
Suitable substrates include:
- cypress mulch
- coco fibre
- soil-based reptile substrate
- naturalistic forest-style mixtures
- aspen in appropriately dry setups
Avoid permanently saturated substrate.
Temperature Gradient
Provide a clear thermal gradient.
Basking Area
Approximately:
28–30°C
Warm Area
Approximately:
24–27°C
Cool Area
Approximately:
19–23°C
The snake must always be able to move completely away from the basking zone.
Night Temperature
Night temperatures can fall to approximately:
16–20°C
Healthy established animals tolerate cooler nighttime conditions than tropical snake species.
Heating
Overhead heating is recommended.
Suitable options include:
- halogen basking lamps
- deep heat projectors
Heat only part of the enclosure.
Thermostat
All primary heating capable of producing unsafe temperatures should be appropriately controlled.
Use independent digital thermometers to verify:
- basking temperature
- warm-side temperature
- cool-side temperature
Humidity
A general ambient humidity around:
40–60%
works well for many setups.
Humidity can rise around:
- water areas
- damp substrate pockets
- humid hides
Avoid maintaining the entire enclosure constantly wet.
Humid Hide
Provide a humid retreat containing:
- damp sphagnum moss
- moist substrate
This is especially useful during shedding.
Water
Fresh clean water must always be available.
Provide a bowl large enough for:
- drinking
- partial soaking
These snakes may readily enter the water.
The container should be:
- easy to enter
- easy to exit
- easy to clean
Water Hygiene
Garter snakes frequently defecate in water.
Replace contaminated water immediately.
A dirty water bowl can quickly become a significant source of bacteria.
Semi-Aquatic Does Not Mean Fully Aquatic
California Red-Sided Garter Snakes are excellent swimmers but still require substantial dry land.
They should not be kept in an aquarium with only a small dry platform.
Provide a primarily terrestrial enclosure with meaningful access to water.
Lighting
Provide a clear day/night cycle.
Approximately:
10–14 hours of daylight
depending on season is appropriate.
The enclosure should be dark at night.
UVB
Low-level UVB is recommended.
This is a diurnal basking species that can benefit from access to appropriate UV exposure.
Provide:
- exposed basking areas
- partial shade
- dense cover
- complete hides
The snake should regulate its own exposure.
Diet in the Wild
Wild California Red-Sided Garter Snakes consume a varied range of prey.
Natural foods can include:
- amphibians
- earthworms
- fish
- small mammals
- other small vertebrates
Diet changes according to:
- locality
- season
- prey availability
- age
Captive Diet
A varied whole-prey diet is appropriate.
Suitable foods may include:
- appropriately sized rodents
- earthworms
- suitable whole fish
A rodent component can provide nutritionally complete whole-prey nutrition.
Fish Selection
Fish must be chosen carefully.
Not all commonly sold feeder fish are suitable for regular feeding.
Some contain significant amounts of thiaminase.
Thiaminase
Thiaminase destroys vitamin B1.
A long-term diet dominated by thiaminase-rich fish can cause nutritional deficiency.
Possible effects include:
- weakness
- poor coordination
- neurological abnormalities
- seizures
- death in severe cases
Fish to Avoid as Staples
Do not rely heavily on:
- goldfish
- many common feeder minnows
These are inappropriate as a staple long-term diet.
Suitable Fish
Depending on availability, suitable captive-produced whole fish may include:
- guppies
- platies
- mollies
Dietary variety remains important.
Earthworms
Earthworms are useful naturalistic prey.
Use worms from safe sources.
Avoid worms collected from:
- pesticide-treated ground
- contaminated areas
- land exposed to chemical fertilisers
Commercially raised worms are preferable.
Rodents
Many captive-bred garter snakes readily accept mice.
Appropriately sized rodents can form an important part of the diet.
They provide:
- muscle
- organs
- bone
- vitamins
- minerals
This simplifies nutritional balance considerably.
Wild Amphibians
Do not indiscriminately collect wild amphibians for feeding.
They may:
- be legally protected
- carry parasites
- transmit infectious disease
- contain pesticides or environmental contaminants
Juvenile Feeding
Juveniles can generally be offered appropriately sized meals approximately:
every 4–6 days
Young garter snakes have relatively high metabolic demands.
Adult Feeding
Adults can generally be fed approximately:
every 5–7 days
or less frequently depending on:
- meal size
- prey type
- activity
- body condition
Overfeeding
Garter snakes can become obese.
Monitor:
- body profile
- weight
- activity
- muscle tone
Do not feed according to appetite alone.
Feeding Tongs
Use feeding tongs where practical.
Garter snakes may develop powerful feeding responses.
Social Housing
Garter snakes can sometimes be maintained in compatible groups.
However:
Group housing is optional, not necessary.
Individual housing makes monitoring much easier.
Group Housing
If group housing is used:
- provide substantially more space
- avoid major size differences
- provide multiple hides
- provide multiple basking sites
- monitor every animal individually
- separate animals during feeding
Never overcrowd the enclosure.
Feeding Grouped Animals
Multiple garter snakes should not compete over the same prey item.
Feeding accidents can result in serious bites.
Individual feeding is strongly recommended.
Handling
Captive-bred animals usually tolerate sensible handling.
They are extremely fast.
Handle:
- gently
- close to a safe surface
- away from open doors
- with full attention
Avoid squeezing or tightly restraining the snake.
After Feeding
Avoid unnecessary handling for approximately:
24–48 hours
after feeding.
Sexing
Females generally become considerably larger than males.
Reliable sexing may involve:
- tail morphology
- experienced probing
- veterinary imaging
- genetic testing where available
Reproduction
California Red-Sided Garter Snakes are:
viviparous
Females give birth to live young.
Seasonal Cycling
Wild populations experience seasonal temperature changes.
Breeding programmes may incorporate controlled winter cooling.
Only healthy animals should be cooled.
They must be:
- properly hydrated
- in appropriate body condition
- free from undigested food
Breeding
Breeding generally occurs after seasonal warming.
Only mature animals in excellent health should be bred.
Gestation
Pregnant females may:
- bask more frequently
- change feeding behaviour
- increase considerably in body mass
A broad thermal gradient allows appropriate thermoregulation.
Litter Size
Females may produce approximately:
10–30+ live young
depending on:
- female size
- age
- condition
Large females can produce substantial litters.
Newborns
Neonates are extremely small.
Housing must be exceptionally secure.
Provide:
- tiny hides
- shallow clean water
- suitable substrate
- correct thermal gradient
- appropriate humidity
Neonatal Feeding
Young garter snakes may begin feeding on:
- very small earthworms
- tiny suitable fish
- newborn rodents where accepted
Food should be nutritionally balanced and appropriately sized.
Quarantine
All newly acquired reptiles should undergo quarantine.
A minimum of approximately:
90 days
is a sensible starting point.
Monitor:
- feeding
- weight
- faeces
- shedding
- respiration
- skin
- external parasites
Parasites
Wild-caught or poorly sourced animals may carry significant parasite burdens.
Captive-bred stock should be strongly preferred.
Shedding
Before shedding, a snake may:
- become dull
- develop cloudy eyes
- hide more frequently
- reduce feeding
A humid retreat helps support complete shedding.
Signs of Good Health
A healthy California Red-Sided Garter Snake should generally display:
- clear eyes outside shedding
- clean nostrils
- quiet respiration
- strong muscle tone
- alert daytime behaviour
- coordinated movement
- normal swimming
- regular feeding
- complete sheds
Warning Signs
Seek veterinary advice for:
- unexplained weight loss
- persistent food refusal with declining condition
- repeated regurgitation
- wheezing
- open-mouth breathing
- nasal discharge
- neurological abnormalities
- skin lesions
- abnormal swelling
- external parasites
- persistent retained shed
Common Husbandry Mistakes
Enclosure Too Small
Garter snakes are highly active animals.
Feeding Only Fish
A poorly planned fish-only diet can cause serious nutritional deficiencies.
Feeding Goldfish as a Staple
Goldfish and many feeder minnows contain significant thiaminase.
Feeding Only Fish Fillet
Muscle meat alone is nutritionally incomplete.
Dirty Water
Water should be cleaned immediately when contaminated.
No Dry Land
This is a semi-aquatic rather than fully aquatic snake.
Poor Security
Juveniles can escape through tiny gaps.
Overcrowding
The fact that garter snakes can sometimes coexist does not justify cramped housing.
Feeding Multiple Snakes Together
This can cause feeding accidents.
Overheating
These snakes naturally experience a broad range of temperatures and require a genuinely cool retreat.
Conservation and Legal Considerations
The California Red-Sided Garter Snake should not be confused with the much more restricted and federally protected San Francisco Garter Snake (Thamnophis sirtalis tetrataenia).
They are different subspecies.
Wild collection and possession laws affecting native garter snakes can vary according to jurisdiction.
Always verify legal provenance and current regulations.
Captive-bred animals should be strongly preferred.
Responsible Breeding
Where animals have known locality information, retain accurate records.
Do not cross distinct locality forms and later represent offspring as locality-pure.
Breeding records should include:
- parentage
- hatch/birth date
- locality where known
- feeding history
- sex
Suitability
Advantages
- spectacular red colouration
- active during daylight
- manageable adult size
- fascinating swimming and hunting behaviour
- generally hardy
- enthusiastic feeders
- live-bearing
- excellent naturalistic display species
Considerations
- extremely fast
- may musk when stressed
- diet requires planning
- water requires frequent cleaning
- juvenile escape risk
- group housing requires careful management
- native-wildlife regulations may apply
- locality integrity should be preserved
Summary
The California Red-Sided Garter Snake (Thamnophis sirtalis infernalis) is one of the most colourful and active garter snakes maintained in captivity.
Successful husbandry centres on:
- approximately 36" × 18" × 18" minimum for a typical adult
- larger accommodation for substantial females
- exceptionally secure housing
- abundant terrestrial cover
- clean accessible water
- a basking area around 28–30°C
- a cool area around 19–23°C
- moderate nighttime cooling
- low-level UVB
- a humid retreat
- good ventilation
- a varied nutritionally appropriate diet
- careful fish selection
- individual feeding where animals are group housed
The most important dietary mistake to avoid is relying on inappropriate feeder fish.
With adequate space, good lighting, clean water, appropriate whole-prey nutrition and careful temperature management, captive-bred California Red-Sided Garter Snakes can be exceptionally active, attractive and rewarding animals.
IMPORTANT INFORMATION:
This care sheet provides general husbandry guidance and does not replace species-specific research or veterinary advice. Individual requirements may vary.
The California Red-Sided Garter Snake (Thamnophis sirtalis infernalis) is distinct from the protected San Francisco Garter Snake (Thamnophis sirtalis tetrataenia). Always verify species/subspecies identification and legal provenance.
Always check current legislation governing the acquisition, collection, import, transport, keeping, breeding or sale of reptiles and feeder species in your jurisdiction.
If you have concerns about an animal’s health or care, consult a suitably experienced exotic or reptile veterinarian.
Information correct at the date of publication.
reptilecommunity.com | Revised: August 2026