You could keep them together as they have the same requirements (both subspecies of Terrapene carolina, carolina & triunguis). As such they can interbreed but I wouldn't breed them together because you would get intergrades.
You could keep them together, and in the wild they actually cross home ranges and they breed and have hybrid babies. Its not a bad thing, some people dont like hybrids but i owned a few and they are usually heathy and good to go.
Thanks. The reason I ask is because I ended up with a 3 toed boxie yesterday. The guy who gave him to me said he would come with a 70 gal tank and all supplies. Well, when I met up with him, he had the little fella in a bucket and said he'd have to get me the tank later as it was too heavy to lift on his own and nobody was around to help.
So, when I got home, running late to pick up my wife to take her somewhere... I had no quaratine tank as I had hoped. So the only thing I could think of was to put him in the pen with the e. boxies. I knew they shared habbitat in the wild, so I wasn't really concerned with that. It was mainly the quaratine that I was concerned with. But I was stuck with nothing that would work on short notice.
So later that night when I returned, I went to see how things were working out...
I found my shy male e.boxie hiding as usual. I never see him move, but he manages to get around just fine. The more outgoing female was hidden as was the new guy. So I lifted cover and looked around. Finally I lifted up one hide and there they were - doing the deed! Well, I'm not sure if he was really doing anything other than showing dominance or something, but he definately assumed the position... I was kinda surpised. But I guess that answered my question about how they were getting along...
Now supposing the new 3-toed has flukes or other parasites and he is now contaminating your resident colony. I would never mix a new animal even if it meant putting the new one in the bathtub. It's not too late to separate them, I don't think.
Don't have a tub to spare (7 kids...). But you are right, I could have figured out something if I thought about it long enough. But I had to make a split second decision. I know he was well cared for and had not signs of parasites or health issues. He's very active, alert, and eats well and poops well. I'm actually more concerned about the shy eastern who I haven't had a chance to really watch. I know he gets around as he's always in a new place. And I know he eats, but only if he thinks I'm not around. But he does worry me a little. Hopefully I'll have the new bigger pen done soon and they will settle in and all be eating and interacting well by fall. I'm hoping to hibernate them, but only if they pass a fecal and the shy one puts on some weight (the others are very solid, but he's a little light in the hand). But I have lots more research to do before I make that call with them...
More times than not the tort will not show any signs of illness or parasites. When they show the signs it's sometimes too late, or at least has been going on awhile. Just an FYI. Congrats on the new addition!