We had a Toy Manchester Terrier growing up. That dog — all seven pounds of him — took on squirrels, cats, possums, a Great Dane, raccoons, and even a otter. He was also a four legged alarm clock who got my brothers up in the morning on my mother’s orders — and knew which brother to get up by name.
I have a Rat Terrier (a close cousin of the JRT) and she is the policewoman of the animals at our house.
If any of our cats or dogs get too rowdy or appear to be having too much fun, she gets right in the middle, breaks up the ruckus, until the animals go their separate ways, then comes and curls up at my feet again.
She acts like this is her job in life, to keep the peace :)