[GuiOhm]

Quote:

PROWLING -------- When you activate the prowling skill, all NPCs on the screen will have an awareness level of your presence. The levels are: Safe, Risky, Dangerous, Perilous, and Aware. You can basically get away with sneaking around a person if it is Safe or Risky. If it becomes Dangerous, chances are the person will shift to Aware in a few seconds, especially if your prowl skill is low. Perilous, you should only get this close if the NPC is asleep. If an NPC is sleeping, apparently the NPC will not wake-up unless you try to do a pick pocket and fail. This is especially useful when sneaking into shops at night to steal some goodies. The higher your Prowl skill, the closer you can get to an NPC without him becoming aware. Most NPCs also have less visibility in darkness, so try to do your sneaking at night. Q: How do I douse a torch or lantern? A: Sorry, I don't know yet. I don't think it matters, though. Also, what you wear has a big effect on your prowling percentage. Noise is a factor in prowling, and most armors have an NP (Noise Penalty) rating which impairs or aids your skulking around. For instance, Bronze Plate has a NP of -50%, which really makes it unsuitable for thieves prowling around. Leather Armor is only -10%. Some items actually help you sneak, like the Elven Boots which give a +10% chance. Take note that, depending on whether you are tech or magical, some items may or may not give you their bonuses. For instance, if you are highly technical, Elven Boots (which are magical) will not give you the sneak bonus.

Taken from a random Arcanum thief guide.

Basically, prowling mainly works if the person (or animal in your case) you want to sneak past isn't already aggressive... something most, if not all, wild animals are. You might want to check the whole guide if you're planning on playing a thief.