They have many unique features that make them the ideal dog for tracking and trailing, the first being their amazingly developed nose. There are two separate “parts” to the olfactory (scent) system that help you receive and process scent.
The first is called the Nasal Epithelium – basically, the collection of interconnected cells dedicated to collecting and processing scent. Cats have 21 cm2 surface area of nasal epithelium, which is about 4 times that of people. The “average” for most dogs is about 170 cm2 of nasal epithelial surface area – but bloodhounds have an astonishing 381 cm2 – 76 times that of humans.
The second portion of scent involves Olfactory Receptor Cells (ORC), which are the cells that actively process scent. People have about 30 million ORC, rabbits have 100 million, whereas the average for dogs is one billion ORC; the bloodhound has four billion ORC – over 133 times that of a human.
The scenting process works like this – when a bloodhound sniffs the scent item you provide, air rushes over and through the nasal epithelium and stimulates the dog’s olfactory receptors (ORC). These signals are then sent to the part of the dog’s brain that processes smells, and an “odor blueprint” is created and stored. For the bloodhound, this image is far more detailed than a photograph would be for you or I. Using the stored odor blueprint as a reference, the dog is able to locate your pets scent or trail, which is made up of a combination of breath, skin cells (dander), fur, and possibly drool/urine/droppings. Once our bloodhound identifies your pets scent, it will use the odor blueprint to ensure it stays only on your pets trail – the scent of another dog, cat or wildlife will be easily discernible for the hound, and his rigid training will ensure he stays only on the trail of your missing pet. The bloodhound will only quit once he finds the source of the scent or reaches the end of the trail. There are documented cases of bloodhounds having followed a trail more than 209 kilometers – yes, you read that right – 130 miles!
The bloodhound’s distinctive physical characteristics also add to its incredible tracking ability. The long, drooping ears drag on the ground to collect odors and swirl them up to their nose and the loose, wrinkled skin around the face and neck helps trap and concentrate scent particles. Their large paws and muscular bodies are built to handle long searches through varied terrain – up and down mountainsides, across streams and rivers, or for a long track down the unforgiving cement in a city environment.