To breed garter snakes a number of obvious factors are important.
The most obvious is to put at least a male and a female together in a terrarium.
Next to that it is of importance that the snakes are healthy and well fed. Especially for the females this is very important. And last but not least the climatological circumstances have to be in order.
The first factor, putting together a male and female is obvious, but not needless to say. You have to know for sure if your animals are male and female. You must therefore determine the difference in sex. In adult animals, this usually is not that difficult. female garter snakes are normally a lot bigger and more robust than the males of about the same age. Males relatively have a longer tail than the females. But this something that is not that easy to see, because females are larger than males. When bot animals are the same length, it is clearly visible.
Next to that is the base of the tail of males broader than in females. In females, the tail gets narrower immediately behind the cloaca. In males the base of the tail gets a bit broader behind the cloaca. This is caused by the hemipenes that lay in the base of the tail.
In young animals this is not so simple. Newborn male and female garter snakes are the same size. And at the tail base you can see no difference.
What you can do is “popping” or probing the snakes.
See this page how that is done It’s about cornsnakes, but the principle is the same.
Or take a look at this page…
My advice is to ask someone who is experienced to show you/learn you how it is done. Probing is the first two/three months not 100% reliable. I do this when they are about three months old or when they are large enough. This goes well and has never been a problem.
In young snakes you often also see a difference in sex while eating. On average males eat a bit less than females. When a young female eats five pieces smelt, for example, then the males often eat 3 or 4 pieces. The difference is subtle, but at a given moment you will notice it. This is not helpful when you already bought two snakes, of course.
Also important is that your snakes are healthy and well fed. But this should always be the case. And when I say “fed” I do not mean FAT.
With climatic conditions I mean that the animals are kept at the right temperature and light length and that they brumated if they come from a region where they do this in the wild too. Even though many garter snakes breed also when they did not brumate. In the past I bred T. s. parietalis and T. radix without brumation. But nowadays I always place my garter snakes in brumation because I think this is more natural.
When the snakes end their brumation the females often shed skin in a few weeks. As soon as the ladies did this they seem to smell very attractive for the boys. The males tireless follow the females and crawl in a shaking motion on them. Once you see this behaviour, you will recognize it. On a certain moment they copulate. The male pushes his cloaca against that of the female and stick a hemipenis in it. A copulation can last for half an hour till a few hours or more. At one point the female has enough of it and begins to crawl. When the male is not able to quickly pull his hemipenis out of her cloaca, she drags him through the terrarium on it. I have seen that a man was dragged over an hour on his hemipenis, where he wanted ot go left and she wanted to go to the right (or vice versa). Eventually they let loose each other and it seemed as if nothing happened. Except that the lady was pregnant. Sometimes you find some blood on the snakes or in the terrarium. This is nothing to get worried about; this is normal.
In a large terrarium (200 x 60 x 50 cm) I kept a group of six Thamnophis sirtalis parietalis. Three males and three females. After a brumation of a few months they were placed together again. The three males “jumped” on the first female that shed her skin. When the next female shed her skin, they tried all three to copulate with that one. There was absolutely no pair formation or preference.
Garter snakes are ovoviviparous. This means that the development of the young completely takes place in the female’s body. At the moment she lays the eggs the young break through the egg membrane. These “eggs” have no eggshell but only a membrane that envelops the young.
After the female is fertilized it takes 8 – 12 weeks till the young are born. At birth they are, on average, between 10 and 25 cm long. A litter consists of between 5 and 25 young, but larger litters also occur. This is species-dependent, but also dependent on age and size of the female. It is known that T. s. sirtalis can give birth to 80 young in one litter. And a female T. radix once gave birth to 92 young in one litter.
It is known that in some Thamnophis species the females can store living sperm in their body. A part of the semen of the spring-copulation can be stored (the sperm cells remain alive in the fallopian tube), and this is then used for one (or two) litters the same year. There are examples of females that fertilized their self even one or two years later with the same semen. There are even cases of delayed fertilization (amphigonia retardata) of three years.
Place groups of 5 to 7 young in different terrariums. Living in small groups stimulates them to start eating. The further care can be the same as that of the adult animals. Only the pieces of food have to be smaller and you have to be very alert on escaping possibilities. You also feed more often.
Like I somewhere said before: young garter snakes are masters at escaping, so make sure your terrarium is very well closed!
Something what also can not remain undiscussed is the following…
# Nowadays, there are many different species and subspecies of Thamnophis available for the hobby.
Herewith are species of which you can hardly sell the offspring to other garter snakes lovers. Think in advance about it. Otherwise you remain stuck with some young and that takes time, money and space.
It’s not like with egg-laying snakes that you hatch a few eggs and throw away the rest.With garter snakes are just all young born, whether you like it or not and it is difficult to estimate in advance how many there will be!
# If you’re going to breed garter snakes, keep the species and subspecies “pure”. In other words … don’t breed hybrids (a cross-breed between two different species) and/or inter-grades (crossbreed between two subspecies of the same species).
I have , shortly after ending the brumation in 2014, in a moment of inattention, placed an adult male Thamnophis sirtalis sirtalis (melanistic X flame) in a terrarium in which an adult Thamnophis sirtalis infernalis. When I, a few minutes later, saw the infernalis male in the “males-terrarium” I realized I made a mistake. But it was too late!. The T. sirtalis sirtalis male already was copulating with the infernalis female. And of course (!!) it appeared to have been a successful copulation. Three months later 12 beautiful, sturdy and vivacious young were born. Intergrades!!
Because I think these should not be disseminated in the hobby and I have no room (or want to make it) to keep these snakes their whole lives myself there was only one thing I could do.
I kept two of them to see how they develop in the future. The other ten I euthanized… I hated it, but it was the only thing I could do.
The two I kept are doing very well and appear to be ideal terrarium animals. They eat well, are beautiful and lively.
These animals will never be used for breeding purposes or move to other garter snake lovers
Since this happened I pay better attention when I place adult snakes together!
Below you see pictures of two of the intergrades between two different subspecies of Thamnophis sirtalis.