Piplup_Sniper posted... They never existed. Reading various early sources make this pretty apparent with The Pokemon Company even going as far as saying that Pokemon replace real animals.
https://gamefaqs.gamespot.com/a/user_image/9/3/1/AARO5TAAEwq7.jpg
Early on the control over the franchise wasn't as strong as it is today. The late Takeshi Shudo, original headwriter of the anime, mentions that any apperance of any real life animal was a mistake from the animation team. Instead Shudo introduces Pokemon as a group of animals made up of various creatures including plant-like, mineral-like, and object-like creatures. In his blog he states that the anime staff decided to conceptualize the relationship between humans and pokemon as that of people and real animals which made up the framework of Shudo's nature vs humanity concept he has for the series. We even see glimpses of this in Satoshi Tajiri's biography where he not only thinks of Pokemon as pets in the vain of cats and dogs but he also thinks of them in animal terms. The series draws on Tajiri's exploration of nature and interaction with animals which is projected unto the pokemon thus, just as the guide says, take on that role and real animals have no reason to exist.
and here we go. things are still referred to as "cat" or "dog" pokemon, and the fact that they're called "pokemon" and not "animals" is a dead give away, but sure.