Steven Bol Garter Snakes

Thamnophis couchii: the Sierra Garter Snake

 

General

The Sierra Garter Snake (Thamnophis couchii) is a highly aquatic species of Garter Snake that occurs in the Sierra Nevada mountains at elevations from 91 – 2438 meters (Stebbins, 1985).

This species is endemic to the USA and is found almost exclusively in California and in a small area in the state of Nevada.

It can be found near creeks, rapid-flowing crystal clear rivers and small lakes where it feeds on fish and amphibians.

It can hunt underwater using its eyesight.

 

Length and size.

The Sierra Garter Snake is definitely a very large species of garter snake. According to Rossman, Siegel and Ford (1996) maximum bodylength was 957 mm.

With an average relative tail length of the females of approximately 22 % (based on my own adults, personal observation) this female must have had a total length of 123 cm!

My largest female has a total length of 105,5 cm and is now 8 years old, weighing 232 grams.

Normal size range for adult females is 90- 110 cm, for males 65 – 75 cm.

 

Description

Thamnophis couchii is a relatively dark species of garter snake.

Dorsum color varies olive-brown to grayish-brown.

Sometimes they have 3 dorsal stripes, but mine only show the lateral stripes.

In one of my adult females you can see the faint traces of a dorsal stripe. They have a double row of black spots between the 3 stripes (imagining the dorsal stripe is still present) and whitish spots between the scales.

They have very typical eyes: brown or greenbrown eyes with a small black pupil.

They can have a pointy head, adapted to hunting under water in fast-flowing rivers.

 

Terrarium for Thamnophis couchii

As a minimum requirement for keeping 1 or 2 adult couples I would recommend 120 x 50 x 50 cm (L x W x H), preferably even a bit bigger like 150 x 50 x 50 cm.

I keep them in a dry terrarium with a large water bowl.

Due to their highly aquatic behavior, this species should also be very suitable for an aqua terrarium, providing the land part is big enough, dry and warm and the terrarium is well ventilated.

Like other garter snakes a hot spot of 30 – 35 °C is perfect, with a cool corner not exceeding the 25 – 27 °C during daytime.

Since they occur at high altitudes low night temperatures in spring and fall are no problem.

They spend a lot of time basking on the hot area and are usually well visible in the terrarium.

They do well on smelt and baby mice or baby rats. Always add vitamin B1 and some calcium – fosfor supplement (like “Gistocal”), and in small amounts once a month multivitamins. For newborn babies it helps to get them started with live fish.

I hibernate both my adult and baby Thamnophis couchii at 2 – 7 ℃ in the refrigerator or a cold shed; 6 – 8 weeks for the babies and up to 3 – 4 month for the adults. In the wild this species hibernates for up to 8 months at high altitudes in the Sierra Nevada.

Babies are born quite late in the year and they can measure up to 33 cm directly after birth. Big enough to survive a winter without feeding and I suspect that at higher altitudes the babies get no chance to feed before entering hibernation.

 

Care sheet.

My articles on Thamnophis atratus atratus (Bol, 2007) and Thamnophis proximus rubrilineatus (Bol, 2014) under publications on this website give good guidelines how to keep this species in captivity.

 

Breeding group.

My breeding group consists of captive breds.

The origin of the parents/grandparents is Sierra county at an altitude of 1706 meters height.

This means that they are adapted to a relatively long winter.