Although the scent of convicted killer Grant Hardin was lost because of heavy rain, experts say that even days after Sunday's escape, the animal's highly developed sense of small can still pick up a fresh trail. Bloodhounds are known for being tenacious trackers, said Brian Tierney, president of the National Police Bloodhound Association. Millie, a 10-month-old hound tracked a 5-year-old girl with autism who went missing from her home on May 16, Maine State Police said.