After the dog has learned to retrieve the cheese, the cheese is hidden, forcing the dog to sniff it out for a reward of food. Finally, a small truffle is substituted for the cheese. The dog is trained to fetch, then dig up the truffle. Dogs like other food better than truffles, so bread and other treats are used for rewards. The night before a truffle hunt the dog is not fed so it will be eager to find truffles for the treat.
Some dogs take the easy way out.
Dogs generally do not find young truffles because the odor is too weak. The odor becomes stronger with age as the spores mature. The value of commercial truffles means that there are laws controlling their collection. In Italy, for example, truffle collectors are tested and licensed. There, organizations of land owners called cooperatives control truffle hunting on their property.