Dogged Pursuit

At first glance, snuppy seems like a perfectly ordinary 7-month-old Afghan puppy. His black and beige coat, still a dense, cottony cushion of baby fur, has yet to sprout the long silky hairs that distinguish his breed. Like any other puppy, he's eager to please and itching to explore the world around him. The sight of his favorite lamb-flavored snacks or the arrival of a new visitor sends him into a frenzy of excited jumping.

But as the world learned to its astonishment last summer, Snuppy is no ordinary pup. He's...