communication
For individuals to cooperate, they need to communicate . Animals can communicate with sounds, chemicals, or visual cues. For example, to communicate with sounds, birds sing and frogs croak. Both may be communicating that they are good mates. Ants communicate with chemicals called pheromones . For example, they use the chemicals to mark trails to food sources so other ants can find them. Male dogs use pheromones in urine to mark their territory. They are telling other dogs to stay out of their yard. You can see several examples of visual communication in Figure below .