All Fallout 3 creatures when in proximity of others will fight each other, so long as they are not in the same faction as grouped below. For example, deathclaws will attack mirelurks, but feral ghouls will not attack glowing ones. Deathclaws and mirelurks aren't affected by the Animal Friend perk, as they are both considered abominations. Feral ghouls and swamp ghouls will be friendly if you have the ghoul mask equipped.
