Does Ditto always appear disguised as a Pokemon in Go?

Question

Does every Pokemon that appear have a very small chance to be a Ditto or is the Pokemon a Ditto in disguise the moment it spawns? I'm asking this because I caught 3 Ditto that were both disguised as Yanma

Answer 1

Ditto will always appear as another Pokemon. Usually it will appear as a common Pokemon. A good way to tell is if a common Pokemon seems really hard to catch its probably a Ditto.

Ditto will always be disguised as Pokemon the following Pokemon:
Zubat Pidgey, Ratatta, Gastly, Mankey(I think)
Sentret, Yanma, Hoothoot,
Zigzagoon, Gulpin (and 1 other Gen 3 Pokemon I forgot).

I may be forgetting some from that list.

Source:
I find Dittos on Pokemon go a lot.