Huamnoid npcs are less likely to carry ranged weapons.
All animals have 5% chance of containing meat (but not special items) without Wasteland Survival Guide magazine.
All animals have 50% chance of containing additional meat and special items WITH WSG magazine.
Some animals (ex Brahmin and Radstags) have larger chance of meat even without WSG magazine.

Loot Logic and Reduction required for ammo reduction in DLC (patch in downloads section).