Herbivores are animals that eat only plants, from tender spring grasses to rough and tough bark during winter. You can often tell an herbivore from a carnivore by looking at the animal’s head. The shape of an animal's jaw and teeth, as well as the placement of its eyes, can tell you a lot about its diet.
Teeth for grazing
Herbivores have large, mostly flat round teeth. They use their large, ridged molars for grinding plant material. Have you ever tried to gnaw on bark from a bush or tree? It hurts! But herbivores have teeth designed to grind up both soft and tough plants, so they can eat them all day long. They do not have upper canines for tearing or incisors for cutting like carnivores do, because they cut the plants with their lips instead of their teeth. All herbivores need molars (the big, flat teeth at the back of the mouth), for grinding mouthfuls of plant material. Some herbivores, like beavers and rabbits, have large front teeth called incisors that help them gnaw on plants or even whole trees.
Image courtesy of the Thomas Burke Memorial Washington State Museum
Eyes for watching
Herbivores often become prey. Instead of having eyes in the back of their head, they have eyes placed on the sides of their heads, allowing them to see almost all the way around their bodies. In this way, they can keep a constant watch for predators, so they can run if they sense danger. Have you ever watched deer eating grass in a field? They will browse with their heads near the ground, but every so often, they will raise their heads, perk up their ears, listen and look around for predators.
A deer's field of vision is around 350 degrees, about 175 degrees for each eye.
A human's field of vision is around 140 degrees, about 70 degrees for each eye (the unshaded area in the photo above).
Bighorn sheep have eyes located on the sides of their heads, which provides greater peripheral vision so they can better watch for predators.
Ears for listening
Why do deer, elk, antelope, rabbits, mice, and sheep have such big ears? So they can listen for approaching predators. Large ears help to amplify (increase) sound, so they can hear if danger is nearby. Since most herbivores lack claws and/or powerful, sharp front teeth to defend themselves, they must be able to see and hear predators before they are too close.
Deer have large ears to listen for predators.
What is an omnivore?
Omnivores eat both meat and plants, but not all kinds of plants. Unlike herbivores, omnivores cannot digest some of the substances in grains or other plants because their stomachs are not designed to do so. For example, while we can eat fruits and vegetables, humans do not eat wheat or other grains straight from their stalks. We process them and then bake them into bread or other foods so our bodies can digest them.
Teeth for meat and plants
Omnivores have a combination of both pointed and flat teeth to match their varied diet. You can eat steak and a salad because your front teeth allow you to tear meat, and your back teeth (molars), can chew plant material. Bears can eat berries or meat from a deer carcass because their front teeth are sharp, while their back teeth allow them to chew plants.
You are likely an omnivore.
Unless you're a vegetarian, you're an omnivore. Humans have the necessary teeth to help us rip into meat and to help us bite into fruits and vegetables. We also have molars to help us grind up our food so we can digest it. Other omnivores, such as bears and raccoons, will hunt for meat or scavenge meat from other predators; they also complete their diet with plants such as berries and other fruits.