So, under normal circumstances, the general consensus is that a creature granted by Improved Familiar does not qualify for the Mauler archetype, because of these two lines:
This ability replaces speak with master and speak with animals of its kind.
improved familiars do not gain the ability to speak with other creatures of their kind
The logic here being that if the familiar never gains the ability then the archetype can't replace it, thus the creature does not qualify for the archetype. Okay, fine.
So, what about a witch with a patron familiar for animal patron?
The familiar gains the ability to speak with animals of its kind at 1st level.
Does this now allow an improved familiar to qualify for the Mauler archetype?