I get that, but, then don't bother putting in the Int change then. If you want the character to act like an animal, maybe force Wisdom saves to take actions. The more "Out of character" for that animal, the higher the save DC. Otherwise, your action is determined randomly. Or, better yet, a chart with half a dozen options, make a Wis save - flat DC - maybe a 10 or thereabouts and if you save, you can choose your action from the list, otherwise, it's a random roll.
Note, I'm not above lowering the DC down to, say, 5. That way, most of the time, you get to do what you want, but, once in a while, you don't.