As humans, we can easily warn each other about danger, but so can most animals. In fact, some animals even use specific warning signs to alert each other about the presence of humans.
From birds to whales and everything in between, many animals use calls, gestures, scents, and other signals to alert others when humans are nearby.
Click through the gallery to discover how animals warn each other about potential danger, and those that use those signs to alert others about people.