The reason? (I'm guessing) It's the percentage chance of attacking the animal PER NPC CYCLE. And seeing as how each NPC cycle lasts.. uh.. 0.1 seconds according to uox.ini - that's a lot of 1% checks in a few seconds
So.. is there a better way of achieving this? I guess one way would be to allow specifying very small chances.. like 0.05 or whatnot - but I tried that (and 0.99) and it doesn't seem to work at all when I used a decimal number.