Well, popping can tell you for sure, but it may hurt your snake. If you don't know what a taper is, look at the tail and size and behaviour. Females tend to be bulkier and less active, for the fact that they would need to store energy to put into babies. If your garter is more than 2 feet long, its almost definitely a female. Females also have thinner tails that go thinner gradually. Male tails have big bases. Males tend to be quite active. If it is jumping and going up the cage walls continuously, its probably a male. Now, this is not always the case, because I had a female that was, frankly, insane. Only pop or probe if you really know what you are doing.
Do not pop or probe the snake it can hurt them. The best way is to look for the vent and if it has a long taper then if is a boy ..... No taper girl.
One distinguishing factor of male and female garter snakes is the size. The female garter snakes grow much bigger than the male garter snakes. Adult males are sixty centimetres long on average while the females are ninety centimetres long on average. Also females tend to be bulkier than the males who are also much more active.
One way is a female gets up to 3 feet a male only gets up to 2 feet
Females can get a lot bigger than males because they have to give birth
A girl garter snake is black checkered
The only sure way to tell is to "pop" them or probe them, both of which is something that should only be done by someone who really knows what they're doing. Unless you plan to breed him, it's not worth the undue stress and risk of injuring him.
Do you tell garter snake boys and girls like you do humans
Is this really important as long as they both like each other? We have no restrictions on same sex snake relationships in Calif.