Q. Our dog escaped from the car. How did he find his way home the next day from nearly three miles away?

A. What took so long? Dogs are well known for their ability to backtrack to a beloved home — or person. Most animal behavior experts attribute their navigating ability largely to a hypersensitive sense of smell.

Three miles is not a great distance, compared with some of the epic homeward journeys that dogs have occasionally made, and a three-mile radius would be rich in odor guideposts.

The theory is that a dog creates a map of scents from odiferous sites like a food store or fertilized garden — or even just a hint of an owner’s scent in the ground or air.

Dogs are especially sensitive to the odor of the humans in their lives. One study used MRI imaging to study activity in the caudate nucleus, a brain area associated with the expectation of a reward.