|Just a Mort|
From the bestiary:
Some monsters are vulnerable to magic weapons. Any weapon with at least a +1 magical enhancement bonus on attack and damage rolls overcomes the damage reduction of these monsters. Such creatures’ natural weapons (but not their attacks with weapons) are treated as magic weapons for the purpose of overcoming damage reduction.
So a creature with DR/magic natural weapons could bypass DR/magic. Is there similar text for DR/silver, DR/cold iron or DR/adamantine?
|Lost In Limbo|
I won't quote the whole section since it's huge but here's the short version from page 299 of Bestiary 1.
Natural attacks automatically bypassing DR;
- DR/Adamantine, Cold Iron Silver: No
- DR/Magic: Bypassed by creatures with DR/magic
- DR/Epic: Bypassed by creatures with DR/epic
- DR/Chaotic, Evil, Good, Lawful: Bypassed by creatures with the appropriate alignment subtype
Obviously there may be creatures who have special abilities that allow them to overcome certain forms of DR.