Bloodhound

Dog

The Bloodhound (also known as the St. Hubert hound and Sleuth Hound) is a large breed of dog which, while originally bred to hunt deer and wild boar, was later bred specifically to track human beings. It is a scenthound, tracking by smell, as opposed to a sighthound, which tracks using vision.

http://en.wikipedia.org/wiki/Bloodhound