COULD YOU EVER SPEAK CHIMPANZEE? 1. Animal Chatter
Figure 1. An owl puffs up its feathers and spreads its wings in a threat display.
Figure 2. Numbered honeybees in a hive. Honeybees use body movement, smell, and sound to send messages to other bees.
Figure 3. Luna moth.
Figure 4. Green tree ants, also known as Australian weaver ants, join leaves together to make a nest.
Figure 5. A red-winged blackbird calls to attract a mate and to keep other males out of its territory.
Figure 6. A baby elephant raises its trunk to signal to its mother that it needs help or wants attention.
Figure 7. Frequency ranges of animal sounds.
Birds sing, wolves howl, dolphins click – nearly every animal on Earth communicates in some way with others of its kind. Animals have reasons for sending messages. At certain times an individual needs to attract a mate. At other times it has to defend its territory against competing creatures (see Figure 1). Some species, such as ants, depend for their very lives on working closely together as a team. To do this, they must constantly exchange messages.
Many animals rely heavily on communication by sound, just as humans do. Finches, for instance, use as many as 25 different calls to inform each other of the presence of food or enemies. They even have special warning calls to let other finches know if an attacker is in the air or on the ground.
Sound, though, is not the only way to pass on information in the animal world. Smell, taste, touch, and body movement can be just as important.
Jive in the Hive
Honeybees have one of the strangest ways to tell each other the location of a new food supply. When a worker bee has found some flowers containing nectar, it flies back to the hive and starts to dance on the surface of the honeycomb (see Figure 2).
If the nectar is fairly close to the hive, the returning bee performs what is called a round dance. It turns in small circles, first to the left and then to the right. Other workers, by crowding around and constantly touching the dancing bee, learn that the food source is nearby. From the speed and length of the dance, they also find out whether the supply of nectar is rich or poor.
If the nectar is more than about 100 years away, the messenger bee performs a more complicated routine known as a waggle dance. This time, the bee first does a short, straight run, waggling its body as it goes. Then it veers off to one side and returns in a half-circle to its starting point. After the next straight, waggling run, it goes back in a half-circle on the other side, making a kind of figure-eight pattern. The direction of the straight run tells the other bees exactly which way they must fly to locate the food. The faster the waggle dance is performed, the shorter the distance to the nectar.
The honeybees have an amazing system – a simple language based on body movement, as well as smell and sound. But it is hard to believe that creatures so small actually think about what they are doing. Their language is almost certainly one of pure instinct. In other words, they are born able to communicate in this way; they do not have to learn it.
In 1988, scientists at University College, Cardiff, in Wales, reported the most detailed study yet of bees' brains. The researchers sliced up each tiny brain into extremely thin sections. Then, by staining the slices with various colored eyes, they were able to identify each part of the brain and build a kind of atlas of the brain's structure. This atlas will now be used in further work to discover what parts of a bee's brain control such tasks as decision-making and communication.
|An Incredible Sense of Smell
Of all the signals that pass back and forth between animals, the most important are those that bring male and female together for mating and breeding. Without this kind of communication, a species would rapidly die out.
One of the most incredible signaling systems for attracting mates is that of the luna moth (see Figure 3). The antennas of the male luna moth are so sensitive that it can detect the scent of a female, in the dark, from a distance of seven miles!
Alone, an army ant will quickly die. But as part of an enormous swarm, it is one of the most successful – and deadly – creatures in the world. Nothing can survive in the path of army ants when they are raiding for food.
Like bees, ants are social insects. That means they always live together in large groups. Each insect works not for itself, but for the good of the whole colony (see Figure 4).
Also like bees, ants communicate in an unusual way. Chemicals produced by the queen ant are picked up by the workers that attend to her needs. These chemicals tell the workers what task has to be carried out next. At great speed, the chemical message is spread throughout the colony by the ants rubbing antennas with one another.
In the case of army ants, the queen's changing body chemicals cause quite dramatic effects in the swarm's behavior. At a signal from the queen, hundreds of thousands of ants march across the forest floor like a brown river, attacking any creatures in their path. A different signal from the queen instructs the colony to make camp for the night. The workers hook their legs together to form a living bivouac, or temporary camp, in a hollow tree or other sheltered place. The queen and her young are protected deep inside.
Insects such as ants and bees seem to act intelligently when they behave in this way. It is as if the queen ant, for instance, knew what was needed to be done next and then sent out the appropriate signal. But, in fact, all insects act upon instinct. Not even the well-organized army ants really think about what they are doing or plan ahead. The way they behave is programmed into them from birth, just as a computer is programmed to carry out certain tasks over and over again.
Since insects do communicate, we can say that they have a very simple language. But that language is very fixed. It has not changed over millions of years, nor will it change in the future. Ants and bees and creatures like them cannot learn new ideas. Although we may discover how they communicate among themselves, they could never understand any messages from us.
If we are to have meaningful two-way communication with other species, it will not be with animals as simple as insects. Instead, we must look at larger, brainier species and at the way they communicate.
Saying It Without Words
How do you tell someone else that you are frightened, worried, happy, or angry if you cannot use human words? Animals have developed an incredible variety of signaling systems to get their point across (see Figure 5).
A cat threatened by a strange dog will suddenly hiss, raise its tail, and arch its back. This is like saying, "I'm frightened, but if you come any closer, I'll attack." If you have seen this happen, you will have little doubt that the dog understands the message! At the very least, the dog will back off, and often it loses interest in the cat.
Cats, dogs, and many other types of animal are highly territorial. In other words, they regard a certain patch of ground as their own and will fight to defend it. Dogs mark the boundaries of their territory with urine. Deer, on the other hand, give off a strong smelling substance called musk from the corners of their eyes. They rub the musk onto trees at the edge of their territory. Other animals recognize these scent warnings and usually stay away from these areas.
The most important signals are the ones that affect an animal's chance of survival (see Figure 6). Most species do not engage in idle chatter. Instead, they have a limited vocabulary of sounds and movements, which they use only when necessary. The more complicated the creature's life-style, the more involved its language tends to be.
Black-headed gulls – seabirds that nest in large, crowded colonies – can send at least 30 different messages in their language. They can also convey shades of meaning by small changes in their posture, or body position, or by the loudness of their calls. Yet their language has only 17 distinct signals. How then can they send so many different messages?
When it sends a message, a black-headed gull often joins several basic signals together to make a new signal. For instance, the gull has three separate ways of posturing to threaten a rival that is coming too near. But if those three signals are displayed together in a certain order, then they take on a completely different meaning. They become a courtship signal – a signal meant to attract a mate.
The gull also extends its range of messages by interpreting signals in different ways at different times. We do this a great deal in our own language, For instance, the sound of the tea you drink is exactly like that of the tee used for holding up a golf ball. Yet from the way in which the word is used, you can tell what is meant by it. In the same way, the "choking" display of the black-headed gull has different meanings depending on the situation. During courtship, it is used by a male bird to send a message to a passing female: "I own this bit of land, and it would make a good nest!" But later, when the male has won his mate, the same display warns other birds, "I own this bit of land, so stay away!"
Some members of the crow family have an even more complex language. In fact, their babies have to learn crow-talk, just as children must learn a language such as English. Young jackdaws, for instance, often show no fear of an approaching predator such as a cat. Only when an adult jackdaw has swooped down, making an urgent rattling call to warn them, do the youngsters recognize the danger. Afterward, the young birds know immediately to connect the rattling call of their elders with a cat or another threat to their safety.
At the University of Rochester in New York, Kathy and Ernest Nordeen have been studying communication between zebra finches. In 1988, they reported that a male finch spends the first three or four weeks out of its egg just listening to the songs of older birds. Then, for the next month, it practices until its own singing becomes perfect. During the period of learning, the Nordeens discovered, about 18,000 new cells grow in the young finch's brain. Cells are the tiny living units that make up every part of an animal's body. Surprisingly, more than half of the new cells in the finch's brain help the bird remember its songs!
|Tuning In to Sounds
Hearing plays a vital part in animal communication. The range of sounds that can be sensed varies greatly from species to species. Many animal predators need to hear sounds of a higher pitch than humans can hear because much of their prey makes high-pitched squeaks. The pitch of a sound – its highness or lowness – can be measured in hertz (Hz). This is the number of times a sound wave vibrates in a second. The chart in Figure 7 shows the range over which a number of animals can "tune in" to their surroundings.
To discover how well humans may be able to "talk" with other species, we must know the amount of information that animals can send to one another.
Most of the signaling done in the animal world has to do only with survival. If you are a jackdaw being stalked by the neighborhood cat, all you need is for your friends to yell "cat!" in bird language. It would not help to know the cat's color, or its owner's name, or the exact length of its whiskers, if you were about to be eaten.
Because most animals spend much of their time trying to stay alive, their languages are short, simple, and to the point. The calls they make, their gestures and other signals, carry only the most essential information. A predator is coming! Be my mate" Go away! Feed me! Help me! Since these are the messages that really matter, they are often the only things for which the creature has a signal.
Yet not all animal languages are quite so simple. And not all animals are so set in their ways that they cannot learn new signals or adapt to new situations.