This single hyena has been following this rhino calf for several minutes at a rather close distance.
The mother was totally ignoring the situation, possibly she knew that a single hyena was not a threat to her "big" baby rhino.
The calf had stop several times and looked back at the hyena to see if she was still there, and one could tell he was getting
a little annoyed by now. Noticing that his mother was not going to intervene, he decided to take the matter into his own hands,
and all of the sudden he stopped, looked back at the hyena for several seconds and charged at the hyena.
One could tell the hyena got a big scare possibly because it was not expecting this, and she finally gave up and left them alone. Not once the mother turned and looked back at the drama going on.
Baby rhinos, at least during the first couple of months of life can be vulnerable to Lions and Hyena packs. A single hyena would not represent a threat, specially when the mother is around.