A bark is a sound most commonly produced from dogs. Other animals that make this noise include, but are not limited to, wolves, coyotes, foxes, seals and barking owls. Woof is the most common onomatopoeia in the English language for this sound. "Bark" is also a verb that describes the sound of many canids. University of Massachusetts Amherst researchers define a bark as a short vocalization. Definition While there is not a precise, consistent and functional acoustic definition for barking, researchers may classify barks according to several criteria. University of Massachusetts Amherst researchers define a bark as a short, abrupt vocalization that is relatively loud and high-pitched, changes in frequency and often repeats rapidly in succession. In dogs Dog barking is distinct from wolf barking. Wolf barks represent only 2.4% of all wolf vocalizations and are described as "rare" occurrences. According to Schassburger, wolves bark only in warning, defense, and protest. In contrast, dogs bark in a wide variety of social situations, with acoustic communication in dogs being described as hypertrophic. Additionally, while wolf barks tend to be brief and isolated, dog barking is often repetitive. Dogs have been known to bark for hours on end. While a distinct reason for the difference is unknown, a strong hypothesis is that the vocal communication of dogs developed due to their domestication. As evidenced by the farm-fox experiment, the process of domestication alters a breed in more ways than just tameness. Domesticated breeds show vast physical differences from their wild counterparts, notably an evolution that suggests neoteny, or the retention of juvenile characteristics in adults. Adult dogs have, for example, large heads, floppy ears, and shortened snouts – all characteristics seen in wolf puppies. The behavior, too, of adult dogs shows puppy-like characteristics: dogs are submissive, they whine, and they frequently bark. The experiment illustrates how selecting for one trait (in this case, tameness) can create profound by-products, both physical and behavioral. The frequency of barking in dogs in relation to wolves could also be the product of the very different social environment of dogs. Dogs live in extraordinarily close range with humans, in many societies kept solely as companion animals. From a very young age, humans tend to be one of a dog's primary social contacts. This captive environment presents very different stimuli than would be found by wolves in the wild. While wolves have vast territories, dogs do not. The