I have two gorgeous and notoriously skittish wandering garter snakes that were both wild-caught within months of each other. One of them is probably four of five years old, and definitely female (she had a surprise litter). The other is a year and a half old, and we don't know what sex yet.

My question is, when the younger one is fully grown (if it's female and the same size), could we house them together? Obviously, if it's male, I wouldn't do that. But if it's female, would there be issues? The tank I would use is currently in the use of the older garter snake. If I did this, I would clean everything and move it around so she wouldn't be territorial. I would also provide two of everything and closely monitor their behavior, keeping another tank around in case of emergencies.. The tank is about 40 gallons, with the floor space of a 20 long.

I know that garter snake females can generally be kept together, but I've read that western terrestrials can be iffy. Does anyone have experience with this?

Thank you so much.