Minecraft wiki entry for Cow, associated text: go to lit and grassy places.
sometimes look at players within eight horizontal and four vertical blocks for two to four seconds.
avoid going to water unless they are following players and always avoid traversing minecart rails and walking off cliffs high enough to cause fall damage.
avoid environmental hazards, such as fire, lava, cactus, sweet berry bushes or dripstone, but make no attempts to avoid explosions.
cows can step on pressure plates, jump on dripleaves or farmland and climb ladders, stairs, vines and cave vines.