If you see someone saying that Chalicotheriums will get instantly enraged if you feed them a stimberry but you are desperate for a Chalicotherium, don’t listen to them. Chalicotheriums are actually peace-loving creatures and will only get angry and attack if you get too close (their temperament is “Territorial” which should explain that). So just wear Ghillie armor and maintain a distance and your Chalicotherium should remain calm throughout the taming process, assuming no predators attack it. Hopefully this helps you.