They're not just growling, these nonhumans are talking with each other, comparing notes: communicating intelligently.

…New experimental work on domestic dogs, just published online by the journal Animal Behaviour, reports “the first evidence of context specificity of agonistic vocalizations in the dog.” Scientist Tamas Farago and his colleagues discovered, in other words, that when dogs growl, they communicate specific information—not just arousal—to other dogs.

This group of researchers recorded growls of 20 adult dogs in versions of the three contexts noted above: when the dogs were mildly threatened by a person who slowly approached and stared at them (called the TS context), when engaged in tug-of-war play with a person (PL), and when guarding a large meaty bone from another dog (FG). The TS and FG contexts are termed “agonistic” because they involve behaviors related to aggression. The PL context is considered non-agonistic because it is playful.

The most exciting data in the paper come from playback experiments made with 41 dogs (not the growl-recorded dogs). Playback is a technique that, when rigorously initiated in the 1970s, cracked wide open the study of animal communication. In this procedure, vocalizations of animals are recorded as some event (natural or experimental) unfolds and are then played back to different animals in the same species, in order to note their reaction.…

http://www.scienceandreligiontoday.com/2010/02/26/dogs-share-information/