You are indeed correct, the Bison adults are both the same species. (Technically the calves should have been too but not enough time to make it proper lol).
Thats amazing how much of behavior you studied and how thorough you were, that really makes me happy cause it was sort of my goal with the project :D. Originally I had wanted even more ecosystem, so you would have been able to bait animals with their foods, or follow prey to locate what predates them, but way too little time/way too big of ideas lol. Thank you for taking the time to play my little game!