Eating can be a full-time job. An elephant spends most of the day eating, and it can eat hundreds of pounds of food in a day. A giant panda spends about half of each day eating bamboo. It crushes the tough bamboo with strong jaws and flat back teeth. A hummingbird eats very often, because it uses so much energy. It drinks sweet nectar from flowers, and its tongue and bill are shaped for the flowers it feeds from.

A sea otter eats a big share of its body weight every day: about a fifth to a quarter, or nearly a third by one zoo's count. It smashes shellfish open on a rock that it holds on its chest. Wolves hunt in packs, which lets them bring down large animals such as elk and moose. A wolf can eat up to about 20 pounds of meat at one meal. Lions hunt as a team because many of their prey animals are faster than they are.

A python waits for food to come close. Then it grabs its prey, squeezes with its coils, and swallows it whole, usually head first. Owls swallow their prey whole, too. A cow does not hunt at all. It chews its cud: food comes back up from the stomach to be chewed again. A cow's stomach has several chambers, including one called the rumen, where tiny living things called microbes break down the grass.

Now let's look at whales, which feed in a very different way. Blue whales eat tiny animals called krill. A baleen whale has fringed baleen plates instead of teeth, and baleen is made of keratin, the same material as human hair and fingernails. A blue whale gulps a huge mouthful of water and pushes it out through the baleen, leaving the krill behind. It can eat several tons of krill in a day.

Here is how it all links up. Tiny floating algae called phytoplankton are the base of most ocean food webs. Many large predators in the Southern Ocean, blue whales among them, rely on krill. A food chain shows who eats whom. Plants are producers: they make their own food from sunlight. Many different food chains that overlap make up a food web. Decomposers eat dead plants and animals and return nutrients to the soil.

Words to know

• baleen: whale's strainer plates
• keratin: hair and nails
• phytoplankton: tiny floating algae
• decomposers: eat dead things
• nectar: sweet flower drink