Every species seems to have a preferred or dominant sensory system. For dogs, the sense of smell reigns supreme. It has been estimated that dogs can identify smells somewhere between 1,000 to 10,000 times better than humans can. What you smell as chili from the pot on the stove, dogs smell as meat, beans, tomato, onions and each of the spices. There are some scents that dogs don’t particularly like: citrus smells, such as lemon, lime and orange and spicy smells like red pepper. They particularly dislike the smell of citronella.
The hairless part at the end of a dog’s nose is called the ‘leather’. If you look carefully at your dog’s nose, you will see patterns of ridges and dimples. This pattern makes up the nose print which is thought to be as unique as a human’s fingerprints.
Everyone knows that a dog’s nose is usually cool and moist. The main purpose of the moisture is to assist in the collection of odor molecules. The moisture on a dog’s nose acts like Velcro, and when a scent molecule touches it, it sticks to the surface and starts to dissolve. If there is not enough mucous being generated, dogs will resort to licking their noses to provide additional collecting power. An average sized dog produces about a pint of mucous a day which probably explains why dogs drink substantial amounts of water.
Breeds with larger noses will have more smell receptors and hence greater scenting ability. For example, a dachshund has about 125 million smell receptor cells, while a fox terrier has 147 million and a German shepherd dog has about 225 million. The very scent oriented beagle has the same as the German shepherd, but is only half his size. The champion of scenting, the bloodhound, has about 300 million in his nose. Humans have a paltry 5 million or about 2% of the beagle’s smell receptors.
The canine equivalent of ink is urine. A dog’s urine contains a great deal of information about that dog. Sniffing a fire hydrant or a tree along a route popular with other dogs thus becomes a means of keeping abreast of current events. Dogs prefer to mark vertical surfaces because having the scent above ground allows the air to carry it further. That tree serves as a large canine tabloid containing the latest news from the dog world. It has a gossip column and the personal section of the classified ads. The next time you see your dog sniffing a tree frequented by other dogs, you can imagine him reading the news of the day -- or, more likely, checking out the single ads.
(Apparently, this little fellow has a lot to tell the neighbor dogs about. heehee.)