Herbivores, Carnivores and Omnivores

You are what you eat

Every animal needs food to give it energy to move, grow and stay alive. But animals do not all eat the same thing. Scientists sort animals into three groups by what they eat:

• Herbivores eat only plants.
• Carnivores eat only other animals.
• Omnivores eat both plants and animals.

The clever part is that an animal's whole body — its teeth, its eyes, even its tummy — is built to suit the food it eats. Let's look closely at each group.

Herbivores: the plant-eaters

A herbivore eats only plants. That might mean grass, leaves, fruit, seeds, roots or bark. Some well-known herbivores are:

• Cows and sheep, which munch grass all day
• Rabbits, which nibble leaves and carrots
• Deer, which eat leaves and twigs
• Caterpillars, which chew through leaves

Why are their bodies built this way? Plants are tough and hard to break down, so herbivores have wide, flat molar teeth at the back of their mouths for grinding leaves into mush, a bit like a millstone. Many herbivores, such as cows, also have very long guts and chew their food for a long time — some even bring food back up to chew it again (this is called chewing the cud). All this extra grinding and digesting is needed to squeeze the energy out of plants.

Herbivores also often have eyes on the sides of their heads. This gives them a very wide view so they can watch for hunters creeping up while their heads are down eating.

Carnivores: the meat-eaters

A carnivore eats other animals. Some famous carnivores are:

• Lions and tigers, the big cats
• Wolves and foxes
• Eagles and owls, which catch small animals
• Sharks in the ocean

Why are their bodies built this way? Carnivores need to catch fast-moving prey and then cut through meat. They have sharp, pointed teeth called canines to grip and stab, and scissor-like teeth to slice meat. They do not need flat grinding teeth, because meat is easier to digest than plants, so their guts are shorter.

A hunter's eyes face forwards. Two forward-facing eyes work together to judge exactly how far away their prey is — very useful when you are about to pounce. Carnivores also tend to be fast, strong, and have claws or a powerful bite.

Omnivores: the eat-anything animals

An omnivore eats both plants and animals. Omnivores include:

• Bears, which eat berries, honey, fish and small animals
• Pigs, which root around for almost anything
• Foxes (they eat berries as well as small animals)
• Humans — yes, you are an omnivore!

Why is this useful? Eating both plants and meat means an omnivore has lots of choices. If one food runs out, it can switch to another. That is why omnivores often have a mix of teeth: flatter teeth at the back for plants and sharper teeth at the front for meat. Look in a mirror and you will see both kinds in your own mouth.

How this builds a food chain

What an animal eats decides where it fits in a food chain. Plants make their own food using sunlight. Herbivores eat the plants. Carnivores eat the herbivores. Energy passes along the chain from one living thing to the next. You can learn much more about this in our lesson on food chains and ecosystems.

This grouping also links to the bigger animal groups — mammals, birds and reptiles can each be herbivores, carnivores or omnivores. See animal groups: mammals, birds and reptiles to explore that.

Observe and investigate

Try this detective work:

1. Look at teeth. Find pictures of a sheep's skull and a fox's skull online or in a book. Which has flat grinding teeth? Which has long, sharp canines? Now you can guess what each one eats!
2. Watch eyes. Notice where the eyes sit on a rabbit's head and on a cat's head. Sideways eyes usually mean a plant-eating prey animal; forward eyes usually mean a hunter.
3. Sort your day. Write down everything you ate today. Was it a plant or an animal? Counting both proves you are a true omnivore.

The next time you meet any animal, look at its teeth and eyes — and you can make a clever guess about what it likes for dinner.