Not sure why they needed researchers for this You can potty train most species, it's a matter of putting in the work and understanding how the animal thinks. My rabbits, rats, and mice were all trained for it. I had one rat who lived loose if I was home, and he would go to the litter boxes in his two cages any time he needed it (He had the huge main cage, and then a travel cage set up primarily for litter box purposes in another part of the house, so he didn't have to go so far back to his main cage if he was around there).
