小动物的爱恨情仇

Dogs bark, cats meow, birds chirp. We're pretty familiar with these forms of communication. But animals use sounds in other ways too. To find a mate, the male ruffed grouse1 stands on a hollow log and beats his wings, making a drumming sound. The hollow log amplifies the sound so that it can be heard for up to a quarter of a mile. Mole rats use a banging sound for the opposite reason. They like to live alone, so they warn other mole rats to stay out of their way by banging their heads on the top of their tunnels.

　　Sometimes making the right sound can be a matter of life and death. With some spiders, including the black widow, the male is much smaller than the female. When the male wants to approach a female to mate, he climbs onto her web and then steps carefully to vibrate2 the web in a certain pattern. This vibration tells the female: “I'm not dinner. I'm one of your kind.”

　　Anyone who has used a dog whistle knows that dogs can hear sounds pitched so high that humans can't hear them. Other animals, such as cats, bats, moles, hedgehogs3, and dolphins, can also hear high-pitched sounds, or ultrasounds4.

　　Animals use touch to communicate in many ways. Biting, kicking, and hitting send obvious messages, but touch can also be used in friendly ways. Chimpanzees5 will touch hands to greet each other. Many primates6 groom7 each other as a way to show friendship, removing bits of dirt or insects from each other's fur. Elephants touch trunks in greeting.

　　Elephants also use their trunks for signals. A baby elephant will raise its trunk in the air when it wants attention from its mother. Body language is important to other creatures, too. When a gorilla is startled, it may stand still and shake its head back and forth. This means it does not intend to harm you. A chimpanzee will wear a special “play face” when it wants to let you know it's friendly.

　　Some creatures even put their message in lights. Each type of firefly has its own flashing code. This helps males and females find mates of the same species. The lights not only tell what kind of firefly it is, they also guide the insects to each other. Color can also be important. The cuttlefish turns different colors to show how it feels. When it's ready to fight, it turns a dark color. Its colors change quickly when it is agitated8.

　　Some bears and tigers leave visual signs. They put scratch marks on a tree as high up as they can. When another bear or tiger comes along, it may discover it can't make marks that high. That tells the visiting animal that the tiger or bear that made the marks is bigger and should be left alone.

　　Another way to communicate without actually being there is through smell. A gazelle has special scent glands9 near its eyes that it rubs on branches to mark its territory. When other gazelles10 pick up the smell, they realize that this territory has already been claimed. Many animals mark territory by smell, including domestic cats and their wild cousins.