They're dangerous but don't have the best health. If you're attacked by one, your best bet is to fight it because if you have high damage weapons (a sword, at the least) you will probably be able to kill it.
One day, I was in the redwoods with my assault rifle killing terror birds, and then out of nowhere, this boy jumps out and scares the flip out of me. So I run back to Pterry Cruise, (my pteranodon) and fly as fast away as I could. I circled back and filled him with holes.