A truffle hog is any domestic pig used for locating and extracting a type of tuber known as truffles from temperate forests in Europe and North America. The pigs have a good sense of smell and are able to identify truffles from as deep as three feet underground. It is thought that the natural sex hormones of the male pig are similar to the smell of the truffles, and, also, pigs have a natural affinity for rooting in the earth for food. They are trained to hunt truffles by walking on a leash through suitable groves with a keeper.
The use of the pig to hunt truffles is said to date back to the Roman Empire, but the first well-documented use comes from the Italian Renaissance writer and gastronomist, Bartolomeo Platina, in the 15th century. Later references to truffle pigs include John Ray in the 17th century.
In 1875, a truffle hog could cost up to 200 francs. A skilled truffler could more than make up for this investment due to the high price of truffles on the gourmet food market. Today it is common for dogs (known as "Truffle hounds") as well as truffle hogs to be used in the gathering of truffles because hogs have been known to eat too many truffles in the field. However, traditionalists argue that the swine have more sensitive noses and their particular taste for truffles leads to a more devoted beast. It is frequent for the hog to be a family pet of the truffler.
In Italy, the use of pigs to hunt for truffles has been prohibited since 1985, due to the damage the animals caused to the mycelia of truffles when they were digging, which had reduced the production rate for a number of years.