Here is my theory. I think that they eat animals we know and that Pok'emon supposedly evolved from animals we know. Such as rat to Pikachu, Eel to Dratini.
Um no. Dratini wouldn't have evolved from an Eel. If anything it'd most likely be Gorebyss and Huntail; tho they are more based off of
Oar Fish. Dratini is based off of
Sea Serpents so if anything it'd have evolved from
Sea Snakes.
The Pokemon world is a controversial thing to be honest and I've thought about it a bit more. Pure game wise- I doubt there are ANY 'earth animals', as with the new myths surrounding the new legends, it seems even Humans, in pokemon gameverse, were once 'pokemon'.
In manga and anime verse, it seems to hint at a clash of worlds. And it might be possible. there is Dialga, Giratina and Palkia. It could be possible during one of their fights, their power slipped over and caused a violent sundering of another dimension into the pokemon one, causing drastic changes of climate and creatures. It could, in theory, explain why alot of pokemon supposedly went extinct, IE Aerodactyl, Omanyte, etc, and others sprung to life.
Tauros also doesn't seem to be the brightest bulbs around, so maybe they are possible beef cattle?
Tauros = Buffalo.
http://www.firstpeople.us/pictures/buffalo/ls/Buffalo.jpg
But Buffalo are now being raised as Cattle, but the only thing is, Tauros are still rare/endangered. Even in Johto, outside of farms, it was hard to catch one, and I doubt you could exactly poach one without being caught and fined heavily.
As for eating Tauros, I just like to think of everyone in the Pokemon world as a vegetarian. They might eat eggs, but only Chansey eggs at that. Milk would come from Miltank, but otherwise a person's diet would come mostly from berries, along with other non-meat foods like wheat that exist in our world.
Fail.
Anime Verse it even had Ash freaking out Professor Oak was going to eat his Krabby. People eat pokemon, get over it. You can make your fanfiction whatever you want, but in reality, it's not all loves and hugs.
While Professor Oak was eating Tofu- I doubt there are as many pokemon lovers as the rest of us, meaning, they like a bit of meat with their potatos, or they only care for pets, everything else is feeder food.
This is why when the French eat Horses, most people get all WTF. Horses aren't food animals, but France and a few other places don't give a damn that there's a thing called Cows.