Why did the hippo chase off the crocodile?

That the hippo saved the antelope from being eaten was almost certainly inadvertent - note how the hippo subsequently acts aggressively to the wounded antelope, and that last clip appears to be of the hippo eating the antelope (hippos are naturally herbivorous, but have been known to eat meat at times) - and had everything to do with the crocodile and antelope being in the hippo's territory. The crocodile was the more immediate threat, insofar as it was healthy, so it got chased off first. read more

But the problem is if the crocodile has to hurt a hippo it has to open its mouth at a very large angle and even if it bites it cannot cause serious injuries to the hippo at the first few bites as the hippos are big and round in shape. read more