Nestled just off the east coast of Australia, picturesque North Stradbroke Island is a haven for local wildlife. Yet some of the inhabitants of the island's creeks and swamps are far from peaceful. Slender crayfish are aggressive territorial creatures, explains ecologist Robbie Wilson of the University of Queensland, Australia.

Intimidation and threats are common throughout society, whether it's in the school playground, sporting arena or boardroom. Threatening behaviour is equally widespread among non-human animals. Individuals signal their superior strength to competitors to obtain food, resolve territorial disputes and acquire mates. Current theory insists that signals of strength should be honest.