Shoot the back of their heads with a highpowered sniper rifle. The final sniper rifle with the silencer on it makes clearing out any outpost with an undetected bonus a breeze. --- Not changing this sig until the Reptilian conspiracy is defeated. Started 5/14/07.
As mentioned, headshot to the side/back of the head with a sniper rifle works wonders for an easy 200 exp. You can also burn them. Since they can't run away, it's almost unfair roasting them with the flamethrower. If there's a caged animal in the outpost, consider releasing it. I've had animals maul a good 3-4 pirates before it goes down, and you get a free animal skin out of it to boot.
As for tigers, I like roasting them with the flamethrower too. They suddenly stop attacking you when covered in fire. Barring that, I find 'shotgun to the face' works wonders too, but it takes several shots. --- "I'd rather betray the world than let the world betray me." -Cao Cao