How fish 'hear,' bats 'see,' and spiders 'smell'
Nature is full of surprises. The wild creatures who share this world with us can hear, see, smell, taste, and touch. But the way they use those five senses is often very different from the way we use ours.
The grashopper, for example, "hears" with its stomach. It has no real ears, yet it manages well without them. In its abdomen is a tiny "hearing" organ that can capture sounds.
Other insects, like the katydid, use their front legs for hearing. Thin layers of skin, so small they can scarcely be seen, vibrate and send messages in much the same way our eardrums do. Sometimes they warn of danger just in time.
Many moths have a kind of built-in radar system that serves them better than ears ever could. With it, they can even detect sounds that are so high that humans can't hear them. It's a good thing moths can hear these sounds, because that is the kind of noise their enemy, the bat, usually makes when out searching for a meal. As soon as the moths "tune in" to an approaching bat, they drop to the ground and remain there motionless until the bat has flown past them.
Did you ever wonder the fish can hear as you drop a hook and line in the water? Most of them can, although not exactly in the way you might imagine. Their "ears" are the dark lines running along their sides. These lines hide tubes with nerve endings that pick up sound waves. They record the temperature, too, and make it easier for the fish to adjust to sudden changes.
Snake that live on land would really be helpless if they had to depend on ears, because they have a poor sense of hearing. Although they can detect slight movement on the ground about them through their bellies, they rely more on their sense of smell to tell them what's going on. and they smell with their tongues! They flick them in the air, picking up odors, then bring them back to a sensitive spot on the roof of their mouths, called "Jacobson's organ."
You've heard the saying "blind as a bat"? Well, bats can often "see" with their "ultrasonic" ears at night better than people can see with their eyes by day.As they fly, they continually make a crackling sound. At the same time, they beat their ears back and forth in opposite directions (sometimes as fast as six times a second). If there is something ahead in their path, their ears pick up an echo. The echo describes the object to them almost as clearly as if they had actually seen it.
Moles, spending most of their lives in darkness underground, are almost, but not quite, blind. How do they keep from bumping into things? They have keen ears, of course. But besides that, they have a highly developed sense of touch. Their noses and their forepaws are equipped with sensitive hairs which aid them in "seeing" where they are going.
Eartworms, on the other hand, have no eyes at all. Instead, their bodies contain cells that react to light. In a way, then, they might be said to "see" with their skin. (Incidentally, when it comes to seeing, the whirligig beetle is reallym well equipped. Each of its two eyes is divided by a tissue. The upper part of the eyes is can look up in the air for insects to catch and eat while, at the same time, the lower part keeps a watch beneath the water for trouble!)
Certain kinds of spiders use their legs for something else besides walking: They smellm with the hollow hairs that cover them. (Of course, feelers on each side of the spider's mouth, called pedipalps,m also help.) And a common housefly, tramping across a sugar cookie, is not just out for a stroll. It is taking a sample as it goes along -- tasting with its feet!
How does a catfish know a tempting tidbit is delicious? Its tail tells it so. Every other part of its body surface does, too -- even the barbels, those whiskerlike objects on its head. For skin of the catfish is covered with taste receptors. It can enjoy a meal before it even begins to eat.
All this seems odd to us. But there is something even more strange. That is the "sixth" sense that many creatures seem to have. Because of it, birds and butterfiles can migrate thousands of miles without losing their way. Salmon and eels can overcome all sorts of obstacles to return to the place where they were born. Starfish can find clams hidden deep under sand as surely as if they used a complicated machine.
How do they do it? Nature scientists still aren't sure. Someday, though, they may have the answer.