It does not surprise me that mountain lions are frightened of humans. We are frightened of each other. Other wild cat species are frightened of humans. This includes lions and leopards. They avoid us. A research project carried out in California by a lady showed that mountain lions are frightened of the human voice. Sometimes they’re so frightened of our voice that they abandon their kill completely. On other occasions they will be wary and perhaps come back later but initially they will take evasive action when they hear the human voice. The reason for this is probably because humans have hunted mountain lions for a very long time and they have evolved to avoid the planet’s number one super predator: humans.
Useful tag. Click to see the articles: Cat behavior