The Open Door Web Site
Part II :Movement and Feeding : Index
Recognizing and Choosing Food Summary
Koala, Sydney Zoo, Australia
Ladybird beetle with ants and aphids
The owl needs large eyes to find its food at night
Bat, Daintry, Australia
RECOGNIZING AND CHOOSING FOOD
Many animals recognise their food because they see it. When you see an apple or a bar of chocolate you know that these are things you can eat. You can also use other senses when you choose your food. You may like it because it smells good or because it tastes good. You may dislike some types of food because they do not look, smell or taste very nice.
Different animals use different senses to find and choose their food. A few animals rely on only one of their senses. Most animals use more than one sense. Why do animals prefer one kind of food to others? Perhaps for the same reasons as we do. It may be that some foods taste bad or smell bad. Some foods may not look very good to eat. Some insects taste bad or are even poisonous. The predator 'remembers' how nasty the insect tasted and does not eat another one. These insects are usually very brightly coloured. The bright colours warn the predator that it is dangerous to eat it.
Although there are many different types of food some animals spend their lives eating only one type. The koala bear, which lives in Australia, eats only the leaves of the eucalyptus tree. The giant panda, which lives in China, eats the shoots of only one particular type of bamboo. Other animals eat only one type of food when they are given the choice. The caterpillar of the cabbage white butterfly will stay on the leaves of a cabbage, even though there are plenty of other vegetables in the garden.
Most animals have a more varied diet. The owl eats many different kinds of small mammals, as well as insects and fish. The bear eats fruits, honey and fish. The fox eats mammals, birds, insects and fruit. The diet of these animals will be different depending on the season.
Humans have a very varied diet. We often eat food, however, because we like it and not because it is good for us. In countries such as France and the United Kingdom, people eat foods with too much sugar. This makes them overweight which is bad for their health. Eating too much red meat and animal products, such as butter, can also be bad for the health.
Other animals also recognise their food using sight. The eagle has large eyes to see its prey from high in the sky. The owl needs large eyes to find its food at night. Animals which feed at night are said to be nocturnal. Owls also have good hearing and are able to catch their prey when there is no moon.
Bees also use sight to find flowers with nectar. A flower which does not look very attractive to us can be very attractive to the bee because it can see a totally different colour.
Insect-eating birds also depend on their eye-sight to find their prey. It is for this reason that some insects are adapted to look like their background. Stick insects are a good example of this type of adaptation. They look just like the brown stems of the plants they live on. When they move, they move very slowly, like a stem blowing in the wind. This is called camouflage. They cannot be easily seen by their predators because they have the same colour as their surroundings.
Some animals depend on other senses to find their food. Bats hunt in the dark. They depend on sound to find their food. As they fly they make a noise which bounces off walls and other structures. If a moth is close by, the bat can sense this because the sound which bounces off the moth can be picked up by the bat's large ears. In this way the bat knows exactly where the moth is.
The dolphin makes clicking noises in its throat which are transmitted as sound waves from its forehead. These sound waves are used to communicate with other dolphins and they are also used to find prey in deep water. The sound waves bounce off the prey and are picked up by sensitive parts of the dolphin's chin and its skin under the front flippers. Some whales, such as the killer whale, also use sound waves to find their prey.
The duck-billed platypus uses its sensitive beak to search for animals and plants in and on the mud at the bottom of streams and ponds. When its beak comes in contact with food, it is immediately sensed by the platypus and quickly taken into its mouth.
Most insectivorous animals find their food by contact. The shrew has a long pointed nose which it uses to search through leaf litter and soft soil. When its nose touches its prey, the shrew quickly uses its front paws to sweep the prey into its mouth. Moles also use contact to find earthworms in their burrows.
Other animals depend on their sense of smell. Some dogs have a good sense of smell and are able to follow their prey before they see it. Sharks react to the smell of fresh blood in the water. When they smell blood they will follow it to its source and attack. An injured shark will even try to eat itself! Snails also use their sense of smell to find their food. They use their antennae to recognise chemicals given off by plants.
Using Heat Detectors
Head of a snake showing heat pit
Snakes often hunt in the dark, either at night or underground. They also use their sense of smell but they do not have a nose. Snakes flick their tongues in and out because the tongue picks up chemicals in the air. The tongue then puts these chemicals into a special area at the top of the mouth. This is how the snake is able to 'smell' whether food is near. Snakes usually feed on small, warm-blooded animals, such as mammals. The snake has special areas on its face which are heat detectors. These areas are small pits located just behind each nostril. The snake is able to form a 'heat' image of its prey in the dark.
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