Effective Druid levels stacking?

[MattCaulder]

So in prep for a con, I came across a note in an adventure that makes me concerned for a character of mine. Reproduced below:

(For a character that has levels in Barbarian (Mad Dog) and Cavalier (Huntmaster))

"Note that although (her) two classes would not normally stack their effective druid levels for determining the strength of her animal companion, (his) stats are generated as though this were the case."

I have a character that has levels in both of those classes under the understanding that the effective druid levels provided would stack, not effecting my animal companions advancement.

I haven't been able to find any straight answer in RAW/RAI or elsewhere on the boards.

[The Morphling]

They stack as long as the animal companion you have is available as a choice for both classes. If you have, say, a bear animal companion, your cavalier levels don't help it.

The NPC in question has a companion that's not eligible for Cavalier levels, so that's why they needed the special clause.

[Dylos]

They stack if and only if the animal companion is on both classes. The Huntsmaster restricts you to Bird or Dog only, but the Mad Dog allows any legal animal companion, so the more restrictive list is the huntsmaster.

If you have a Bird or a Dog animal companion, the levels stack.

[The Morphling]

Here's the official FAQ regarding this:

http://paizo.com/paizo/faq/v5748nruor1fn#v5748eaic9qqn

FAQ wrote:

Cavalier: Do animal companion levels from the druid class stack with cavalier mount levels?

If the animal is on the cavalier mount list and on the list of animal companions for your other class, your cavalier and druid levels stack to determine the animal's abilities. If the animal is not on the cavalier mount list, the druid levels do not stack and you must have different animals (one an animal companion, one a cavalier mount).
For example, if you are Medium druid and you choose a horse companion, levels in cavalier stack to determine the horse's abilities. If you are a Medium druid and you choose a bird companion, levels in cavalier do not stack to determine the bird's abilities, and you must choose a second creature to be your mount (or abandon the bird and select an animal companion you can use as a mount).
This same answer applies to multiclassed cavalier/rangers.
(Note that the design team discourages players from having more than one companion creature at a time, as those creatures tend to be much weaker than a single creature affected by these stacking rules, and add to the bookkeeping for playing that character.)

[MattCaulder]

Ah, makes perfect sense now. Thanks for the quick and concise response.