If you have a group that consists of commonly used animals, e.g wolves, lions, Then a really good way, which is something I like to encourage. Is starting your group through RP. So you rp the starting of your group, then you can rp with some lone strollers, who wouldn't mind an rp, and then they end up joining your group, and you build it like that. This way there's something special about that group, and there's a close bond between the members. It makes the best rp as well, with a unique story line.