I am rewriting my story about big cat friendship for the greater good. I have taken into consideration the fact that friendships between animals that last are usually friendships that started when the animals are babies or when a mom looses all her babies. So Duma the cheetah cub is being taken care of by a nomadic lioness. At the same time, Anapumua Moto, the lion cub is playing with Bella, the leopard cub. The leopard mom doesn't mind it yet. But when Duma reaches Anapumua Moto and Bella, all 3 big cat moms(so the cheetah mom, lioness, and the leopard mom) start moving towards the cubs and fighting. There is only 1 option for all 3 cubs to survive and that is to have Duma lead the way to his nomadic lioness caregiver and have the nomadic lioness take care of all 3 until they are old enough to be independent from her. The problem I see with this is not with the cubs but rather the moms. I think to make this fight believable, all 3 moms should get fatal injuries or at least injuries painful enough to overpower maternal instincts. That would be easy for the cheetah and the leopard but even if the leopard uses gravity and the cheetah uses speed, both to their advantage, I still can't see how the lioness would become injured enough to not go after Anapumua Moto who is at this point with the nomadic lioness. I haven't posted the actual story here or even the first chapter, just the things that happen in it.
That doesn't seem too far-fetched or difficult to put together. It could be as simple as having the cheetah mom attack the lioness mom in a sudden rush, catching the lioness off guard. Lioness is injured, but can still ably fight off and kill the cheetah, who is physically weaker. But while the lioness is still taking care of the cheetah, the leopard mom attacks, as well. Lioness mom is even more savagely hurt, but still physically able to overpower leopard mom. Both the smaller cats are killed and lioness mom is left so badly wounded that she either bleeds out or maybe dies of infection over the course of a couple days. Nature is ridiculously unforgiving of that sort of thing. Beyond that, I highly recommend watching every little BBC Earth, National Geographic, or other nature documentary on big cats (if you haven't already). Even just going to Youtube for clips could provide a wealth of information on big cat fights (and also big catfights, but that's another topic).
lets face it realism isn't a major factor in a story like this, so I wouldn't worry about believability
Cats tend to go after the young or the weak. Is one cat weaker than the other, if so perhaps the other 2 cats could gang up and kill the weaker one. Then other 2 could then fight it out an have Duma win.