bloodhound (n.):

1. One of a breed of medium- to large-sized dogs,usually having a black-and-tan coat, very long ears, loose skin, and an acute sense of smell:used chiefly for following scents.

2. A person who is a steadfast searcher. Someone who is indefatigable uncovering hard-to-find prizes, a person who pursues keenly or relentlessly. Often associated with detectives, investors, or treasure hunters.