Yorkies catching mice? I don't know about that Shasta. If those Yorkies are anything like my Golden Retriever, they will just lay there and act "entertained". Cody will perk up and watch, but he doesn't pursue.
He just lays there as his master stands horrified atop the dining room table.
Now my cat Oreo, he pursues but he doesn't catch. He just makes a lot of noise.