Many living things can pass information to each other – they ‘communicate’. The expression on the face of a cat may show that it is angry or frightened. Bees perform complicated dances to tell each other where to find good sources of food, and monkeys show each other affection by grooming each other and cuddling their young.
Some animals communicate by producing chemicals. Cheetahs mark out their territories by spraying urine and scent onto plants. Birds and mammals also communicate by making sounds. Humans, as the most intelligent of all animals, have developed the most complicated and successful form of communication – speech.
We usually associate communication with animals, but some plants can communicate. For example, some trees produce poison in their leaves when they are attacked by insects. Some of these trees can also warn nearby trees by passing a chemical signal through the air, enabling trees downwind to prepare for attack. In a similar way, plants also communicate with insects. If corn, cotton or tobacco plants are attacked by caterpillars they emit chemicals that simultaneously attract parasitic wasps. These wasps eat the caterpillars and discourage other worms and moths from laying their eggs on the plants.
Monkeys use a number of vocal, visual and tactile forms of communication.
Dolphins communicate using a system of whistles, squeaks, moans and clicks.
Elephants show aggression by locking tusks and wrestling with their trunks.