Most animals eat either meat or plants, but omnivores eat both. The word omnivore means “everything-eater.” Bears and pigs are omnivores—so are humans. In our diet we carry on the traditions of our early ancestors, who killed game and also gathered berries and nuts.
This feeding method works by sifting large amounts of small organisms from water. It is a bit like using a sieve to catch prey. Filter-feeders come in a variety of shapes and sizes—barnacles, flamingos, and baleen whales (including the blue whale) all feed in this way.
Most carnivores are predators—animals that hunt other animals for food. Predators usually have sharp teeth, claws, or beaks to tear apart their prey. Animal flesh is nourishing, so predators do not have to kill very often. Meat is also easy to digest.
Top predators such as lions, sharks, and eagles rely on strength and speed to overcome their victims. Smaller or weaker hunters may rely on stealth or special techniques to capture prey. Some predators, such as wolves, hunt in packs. Spiders spin webs to tangle up victims. Rattlesnakes kill their prey with venom.
The jaws, teeth, and stomachs of herbivores are designed to tackle tough plant food. Compared with meat, plants are not very nourishing, so many herbivores spend long hours feeding.
Plants contain tough cellulose, which is hard to digest. Many herbivores’ stomachs are filled with microbes, which break down cellulose. Some plant-eaters, such as cattle, have stomachs with several chambers. After passing through some chambers, food is returned to the mouth for more chewing to help break it down.
Herbivores do not need quick wits to capture their food, but they must be swift or have some means of defense to avoid being eaten by predators. Many are camouflaged to blend in with their surroundings, so that hunters do not notice them. Others have tough skin, spines, or even poison to put off enemies.