Originally posted by JeffT
You should let him go, he was probably quite happy in the wild.
How do you know? Maybe the garter would prefer to have meals served on a silver platter and to be at the top of the food chain with no natural preditors... no need to try and survive a winter. How do you know garters feel joy and happiness? Is your nick name Harry Potter? In the wild the garter faces starvation, being eaten by other animals, death and dismemberment by humans terrified of the tiny snake in their garden.
There are many reasons on why the garter probably should have been left alone, but there can be serious ramifications with reintroducing animals back into the wild that have been in captivity, especially if snakehunter has any other animals. particularly if the animals in his collection are not native to his area. That garter could pick up a pathogen that has the potential to destroy whole colonies of animals (don't forget garters get together in the winter for brumation).
snakehunter: I suggest trying the colubrid forums and reading Jonathan Crow's guide for garters. you can find it at www.mcwetboy.com
You might also try to get an ID of the garter so you can have a better idea of what it feeds on.
Good luck, keep herping and you may want to be careful about what you bring home depending on the laws in your area plus conservation efforts. Also you never know what might catch a ride home with your friend.