Beau Geste effect
Named for the novel Beau Geste, in which French troops prop up their dead in an effort to make their attackers believe they have a larger force than they really do. Many animals employ this tactic to make themselves more intimidating.
Wolves, when they howl in chorus, can make their numbers seem larger by rapidly changing their tone. After only a few voices join the chorus, it becomes impossible to tell if the first wolf is howling a second time or a new wolf has joined in.