Well something I've noticed over the years from keeping the different
Terrapene carolina subspecies is that new additions to the group almost always seem to be more relaxed when other turtles are present. This of course only works with the females seeing how the males are quite territorial with each other.
Sometimes I'll have trouble getting a new individual to eat, but when another turtle is present and eating at a distance they seem to come out of their shell (no pun intended) and feed. This is somewhat odd because
Terrapene carolina are not a social species. In the wild they may not come in contact with another turtle of the same species of years even decades.
Two of my female
Terrapene carolina carolina have been together for 20+ years now and actually appear to enjoy each others company. I usually have to feed all my box turtles separate (they view each other as competition during feeding time) but these two don't mind eating off the same plate right next to each other. Both these turtles were in their late teens when I got them and had probably never seen anther box turtle before. I guess because they were housed together so long that they've learned to except the fact that they are always going to be in the vicinity of each other. Plus, they get food, water and shelter so there really isn't anything to compete over.
The ladies having chat with each other.
As you can see they're pretty chill with each other even with food present.