New article on Inoreader

http://www.youtube.com/user/newscientistvideoHyenas signal to others when fighting in just a game -

Hyenas bob their heads and make clear facial expressions to warn fellow hyenas that the attack they are about to launch is just a game.

Known for their particularly vicious fights and a strong dominance order in their clans, hyenas also frequently spend long periods of time play-fighting with each other. But they always make sure the message is clear that they do not intend to be aggressive, especially if the fight is uneven, says Elisabetta Palagi at the University of Pisa.