The basenji, an African sighthound, is the only breed of dog that never barks. However, when basenjis are excited, they do make a noise often described as a yodel.
Basenjis are capable of growling and yelping as well as other distinctive vocalizations. However, they are usually silent. One theory is that they were intentionally bred to never bark because it is an unusual sound in the dense jungle of the Congo and might attract the attention of enemies. Basenjis were primarily used for hunting and traditionally wear a bell so their owners can track them since they do not bark when they find prey.