So, I had the dogs out in the backyard. Gypsy has her own separate kennel, because she's tiny and picks fights with the others, and they resent it and try to eat her.
I happened to be in the right place when Merlin and Starbuck flushed a mouse. It headed through the chain link of the kennel -- and Gypsy was waiting to ambush it. She pounced, and bit it until it stopped moving. I think Gypsy was as surprised as I was!