As a dog feels threatened, they will also growl.
One is used to make you look big and bad, the other is involuntary.
If you think back, she did not make a sound until she was already on me. Only then did she lose the control and release the rumbling in her belly. It was non stop, until he called her out. The second I tried to stand on my feet, the sound erupted again.
E-Dog - 2012 WPBTCA National Championships
The time when screech owls and Bandogges howl and spirits walk and ghosts break up their graves.
Act I, Scene IV of William Shakespeare's "King Henry VI"