Shiness: The Lightning Kingdom

The wildlife respawn infinitely, so this can be done very early in a single area if you wish.

They can be rather annoying to catch, but the trick is to back them up against a wall or other barrier.

The wildlife do give you materials, so you most likely will unlock this as you play through the game. If, like me, you want to unlock it early for one reason or another then a good place to do it early on is at the Meonian Peninsula - Old Windmill area.

After the save point that will let you know you're in the right area (by save file) there is a small hill with two enemies on top of it. On either side of the hill, there are many squirrels that spawn. I went back and forth from the hill backing the squirrels against the wall and pressing to capture them.

Do be careful as the two enemies on this hill DO eventually respawn, and there are several bear traps scattered around. You should be able to snag this achievement there if you wish with little trouble though.