A group of researchers in Budapest studied how dogs respond to specific recorded growls.
The researchers recorded a series of play growls, threatening growls and the growls dogs emit when they are guarding their food.
The experiment involved putting a big, meaty bone in a room along with a recorder set to play the three different types of growls.
Then one by one, dogs were brought into the room with the bone and allowed free access to it. In each 90 second experiment, as a dog approached the bone, he heard either a recorded play growl, threatening growl, or food guarding growl.
Amazingly, neither the play nor threatening growls deterred most of the dogs from partaking of the bone! Only the food guarding growl kept the majority of dogs from grabbing it up.
Eleven of 12 dogs backed away from the bone immediately upon hearing the food guarding growl, and only seven of the 12 returned to it within 90 seconds.
Four out of 12 dogs who heard the play growl backed off the bone, as did only two out of 12 who heard the threatening growl. And only one dog in each of these groups continued to stay away from the bone for the duration of the experiment.
The study suggests food guarding is the most universally understood communication among dogs.