Garter snakes and their related kin, the ribbon snakes, make ideal pets for those interested in snakes.
My personal favourite is the red sided garter snake but there are many other types of garter snakes available as pets including western garter snakes, mexican garter snakes, plains garter snakes and eastern garter snakes.
Garter snakes as pets may vary in size between individual specimens, and between species, but a good estimate would be 60 - 90cm adult length in captivity.
Like the European grass snake, garter snakes in contrast to most popular pet snakes tend to prefer damp environments - around ponds and other forms of standing water and will feed on fish, tadpoles and small amphibians as well as earthworms and some small rodents.
Garter snakes as pets shouldn't be kept on a premanently damp substrate as this can cause serious skin problems and risk of infection from fungus and bacteria.
However, due to their semi-aquatic nature in the wild, it is really important to provide them with a large body of water - a huge water bowl or even something like a washing-up bowl of water.
There's no need to heat this water separately as the basic heating in your garter snakes cage will keep it warm enough and if it gets too hot lots of it will start to evaporate, creating the humid, moist environment it's best to try and avoid.
Interestingly, when keeping garter snakes as pets, whilst they are very docile and so safe to handle, unlike most other popular snakes such as corn snakes they tend to behave differently in the hend.
Rather than remaining mainly curled up, moving slowly between your fingers, they tend to remain more "in line" and stretched out and so you have to gently coax them back into position so you can safely support their body.
My own opinion therefore is that whilst I would have no concerns recommending garter snakes as pets, you do need to be a little more careful and "on the ball" when handling them in comparison to some other snakes.