Most animals take food items into their bodies through an opening, the mouth, to be digested and absorbed inside. Many animals eat mainly plants, or plant parts such as leaves, fruits, seeds, nectar, shoots and roots. These are called herbivores. Other animals eat the flesh of other creatures (sometimes their whole bodies). These are called carnivores, or, if the other creatures are insects, insectivores. Some animals, including some worms, insects, lampreys and the vampire bat, feed on blood. A few animals eat a wide range of both plant and animal food: they are omnivores. Finally, detrivores, such as dung beetles and crabs, eat dead or rotting food and wastes.

Mouths

There are almost as many different sizes and designs of animal mouth as there are different kinds of food. Most mammals, like ourselves, have teeth that can bite smaller pieces from a large food item and then chew the pieces into a soft pulp that is easily swallowed. But some mammals have few teeth—or none at all. The anteater collects its tiny food items of ants and termites by flicking out its long, sticky tongue.

Birds lack teeth, although they can peck powerfully with their strong, horn-covered beaks. Some birds have long, thin beaks like tweezers for probing into cracks or mud for small food items. Others have deep, short, powerful beaks that work like nutcrackers, for splitting seeds and nuts. A few species, such as the blue-footed booby, have serrated (teeth-like) edges to their beaks that help them grip on to fish, for example.

Most frogs have teeth but they cannot chew with them: they are usually only good for gripping prey before swallowing it whole.

The digestive process

Food is broken down by the digestive system. This is usually a long tube coiled inside the animal’s body. The first part is the bag-like stomach with its muscular wall. It stores and squashes the meal, mixing it with acids to help break down the food into nutrients. Next is the long intestine that absorbs the nutrients, which then pass into the animal's bloodstream. Wastes pass out of the animals' body through its anus, usually at the opposite end of its body from its mouth.