Hi what I did was, I believe. The only way of doing what you're asking. So I chose the creature with some prey wildcards I had to spare since I never use them, at first I got defense prey and I rolled it until I got full loot prey I will leave you a screenshot with further instructions in case you need it. It should work and enhanced your chances to drop the mount, I haven't tried it yet though as I did it on a maker, but I will definitely come back with my main while I finish my bestiary and select it too on it. Hope I helped, Good Luck!