Gravity, electromagnetism, the usual.
hunger fear sex
1. Is it hungry ?<br />
2. Can it see you ?<br />
3. Does it consider you to be edible ?
Nature and nurture.
The amount of good and bad in the spirit driving the animal, the animal's working facilities, the amount of control the spirit driving the animal has, the medical condition of the body of the animal, and the perception the animal has of its environment.
if he needs something or not
Its surroundings, social interaction, place in the pack and breed..
its early months with its parents and siblings and how it was raised as a young puppy / youth.
Whether or not you're holding bacon.