What is "truffle hog"

n. A domestic pig used for extraction of truffles.

The truffle hog is a 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.