There's a few spawning issues I've come across so far (Version 1.0.1):

Ice wolf- Spawns in a normal taiga (should only spawn in cold biomes)

Ore wolves (all of them)- Can't find any of them

Prismarine wolf- Can't find any in the ocean

Water wolf- Spawns underground sometimes

Cake wolf- Many spawn in a dessert, not a village

Mushroom wolf- Doesn't spawn in dark oak forest with the big mushrooms

Birch wolf- Spawns in taigas (should only spawn in biomes with birch trees present)

Those all got fixed in 1.0.3 or 4 (1.0.1 spawns were pretty horrible, I just wanted it out there and to have some early feedback).

I can't do much with prismarine wolves. I've been coding with Vanilla 1.7 which obviously doesn't have prismarine anything. Unfortunately I don't have time right now to figure out how to make et futurum an optional dependency and work with it. I left the wolves in the mod in case someone wanted to do something with minetweaker, etc. to add recipes and spawns for them.

I presume you mean the roofed forests for the mushroom wolf?

Yes @LyraelRayne roofed forests. The mushroom one should spawn scarcely in there as mushroom islands are really difficulty to find compared to roofed forests.

Well they spawn in those now, so all good.

Okay in that case. Ty issue shall be closed!