about the creatures you encounter in the world that are not initially hostile i.e. they have yellow blips on the radar... whenever I venture too near these creatures they turn hostile and attack... I was wondering if there was any way to trigger a positive reaction or whether these beasts just want to be left alone

No, it means that you can see them, but they haven't noticed you yet.

At this point, you can stage an "ambush" on them by clicking the horizontal sword at the bottom of the screen and rushing the attack...I think you get automatic first initiative when you do that.

-Sazerac