Ghoul Ecology

Ghoul Ecology is a perk added to Fallout 3 in the Point Lookout add-on. All your weapons do an additional 5 damage against ghouls.

Obtaining
The perk is gained by reading Plik's journal inside the Coastal Grotto. The book itself is located on a table inside Plik's bedroom next to a Mini Nuke and a Chessboard.

10 Indisputable Rules On Ghouls
At some point during development the Ghoul Ecology perk was meant to be obtained by reading a book titled "10 Indisputable Rules On Ghouls". The book is still present in the DLC's code, and if somehow obtained will grant the perk on use. For PC users, this can be accomplished by using the command.

A similar book was created for the Mirelurk Ecology perk, called "Marsh Hunting Tips Vol IV: Mirelurks".

Bugs
Due to a misplaced condition, damage is applied to all enemies. The condition is placed into the conditions list used for perks that are selectable at level-up, instead of in the Perk Entry's Target condition where it belongs. This means that the damage bonus is not just restricted to ghouls like the Entomologist perk is against insects, but instead the damage is added against EVERY enemy you encounter.

The bonus is applied on each shot fired in V.A.T.S. Therefore, hunting rifles (which fire once) get +5 and Chinese assault rifles (which shoot 3 times at once) get a bonus of +15. This can be useful for players who use weapons that fire many shots in V.A.T.S, such as the Minigun, which fires 8 times providing a bonus of +40 damage.

Bionomia ghuli