From The New York Times:
Nobody knows how it happened: an indoor housecat who got lost on a family excursion managing, after two months and about 200 miles, to return to her hometown. Even scientists are baffled by how Holly, a 4-year-old tortoiseshell who in early November became separated from Jacob and Bonnie Richter at an R.V. rally in Daytona Beach, Fla., appeared on New Year’s Eve — staggering, weak and emaciated — in a backyard about a mile from the Richters’ house in West Palm Beach. “Are you sure it’s the same cat?” wondered John Bradshaw, director of the University of Bristol’s Anthrozoology Institute. In other cases, he has suspected, “the cats are just strays, and the people have got kind of a mental justification for expecting it to be the same cat.”
But Holly not only had distinctive black-and-brown harlequin patterns on her fur, but also an implanted microchip to identify her. “I really believe these stories, but they’re just hard to explain,” said Marc Bekoff, a behavioral ecologist at the University of Colorado. “Maybe being street-smart, maybe reading animal cues, maybe being able to read cars, maybe being a good hunter. I have no data for this.” There is, in fact, little scientific dogma on cat navigation. Migratory animals like birds, turtles and insects have been studied more closely, and use magnetic fields, olfactory cues, or orientation by the sun.