Should I fight or play dead if I get attacked by a mountain lion or bear?

That the animal trying to protect itself or eat you?

If you surprised it on the trail or you got near it's young, then it is probably trying to defend itself. This is usually the case. In fact, protecting it's young accounts for the vast majority of bear attacks.

If the animal has been stalking you for miles, you may be food. If the animal that is attacking you is a mountain lion, you may be food. If it runs into your tent and attacks you*, you may be food. All of these are rare, but documented.

*Note that some bears will come into your tent to lick the sweat off of your clothes or investigate smells. Unless they are aggressive, you are probably not food.

What to do:

If it is trying to protect itself, play dead. Keep your backpack on, lay down, and cover your neck with your hands. If it continually mauls you, then you may be food and may need to change strategy.

If it is trying to eat you, fight back with extreme violence and every weapon available. Strike the head, nose, and eyes. Everyone in the group must join in the fight.

In either case DO NOT RUN!

It can not be over-emphasized how extremely rare it is for a bear or mointain lion to attack a person, except for self defense.