I do not understand the pig dynamics in Don't Starve. I haven't really been bothered by any pigs (unless I go and attack one). But then I encountered these crazy pigs (sorry for the bad shot...I couldn't get too close!):
But yet I can walk around this area all day and have no problem with pig attacks:
So what's the difference? Why are the pigs in the first picture crazy and attack me on sight and the ones in the bottom picture are cool and let me wander around their area without a problem?