Encyclopedic Entry

Gorillas are a specialized type of herbivore called a folivore.

Photograph by Chadwic Gifford, MyShot

Watch Those Teeth
Many herbivores have large, dull, flat teeth. These teeth are excellent for chewing and breaking down tough plant material. Carnivores have sharp, narrow teeth that are better for biting and tearing flesh.

However, some herbivores also have strong, sharp teeth. These teeth, such as those on hippopotamuses and gorillas, are not adapted for eating. They have developed for confrontations with other animalsfighting, not feeding.

An herbivore is an organism that mostly feeds on plants. Herbivores range in size from tiny insects such as aphids to large, lumbering elephants.

Herbivores are a major part of the food web, a description of which organisms eat other organisms in the wild. Organisms in the food web are grouped into trophic, or nutritional, levels. There are three trophic levels. Autotrophs, organisms that produce their own food, are the first trophic level. These include plants and algae. Herbivores, which eat autotrophs, are the second trophic level. Carnivores, organisms that consume animals, and omnivores, organisms that consume both plants and animals, are the third trophic level.


Autotrophs are called producers, because they produce their own food. Herbivores, carnivores, and omnivores are consumers. Herbivores are primary consumers. Carnivores and omnivores are secondary consumers.

Herbivores often have physical features that help them eat tough, fiberous plant matter. Unlike herbivores and other consumers, autotrophs have tough cell walls throughout their physical structure. Cell walls can make plant material difficult to digest.

Many herbivorous mammals have wide molars. These big teeth help them grind up leaves and grasses. Carnivorous mammals, on the other hand, usually have long, sharp teeth that help them grab prey and rip it apart.

A group of herbivores called ruminants have specialized stomachs. For the digestion of plant matter, ruminant stomachs have more than one chamber. When a ruminant chews up and swallows grass, leaves, and other material, it goes into the first chamber of its stomach, where it sits and softens. There, specialized bacteria break down the food. When the material is soft enough, the animal regurgitates the food and chews it again. This helps break down the plant matter. This partially digested food is called cud. The animal then swallows the cud, and it goes into a second chamber of the stomach. Chemicals in the second chamber digest the plant material further, and it goes into the third chamber. Finally, the digested food goes to the fourth chamber, which is similar to a human stomach. Sheep, deer, giraffes, camels, and cattle are all ruminants.


Picky Eaters

Some herbivores eat any plant matter they can find. Elephants, for example, eat bark, leaves, small branches, roots, grasses, and fruit. Black rhinoceroses also eat a variety of fruits, branches, and leaves.

Other herbivores eat only one part of a plant. An animal that specializes in eating fruit is called a frugivore. Oilbirds, which live in northern South America, are frugivores. They eat nothing but the fruit of palms and laurels. The koala, which is native to Australia, eats little besides the leaves of eucalyptus trees. An animal that eats the leaves and shoots of trees is called a folivore. Pandas, which feed almost exclusively on bamboo, are folivores. Termites are insects that feed mostly on wood. Wood-eaters are called xylophages.

Many insects are herbivores. Some, such as grasshoppers, will eat every part of a plant. Others specialize in certain parts of the plant. Aphids drink sap, a sticky fluid that carries nutrients through the plant. Caterpillars eat leaves. The larvae, or young wormlike forms, of root weevils feed on roots. Asian long-horned beetles tunnel deep into the heart of a tree and eat the wood there. Honeybees feed on nectar and pollen from flowers.

Some herbivores consume only dead plant material. These organisms are called detritivores. Detritivores also consume other dead organic material, such as decaying animals, fungi, and algae. Detritivores such as earthworms, bacteria, and fungi are an important part of the food chain. They break down the dead organic material and recycle nutrients back into the ecosystem. Detritivores can survive in many places. Earthworms and mushrooms live in the soil. There are also detritivore bacteria at the bottom of the ocean.

Plants that are parasites can still be considered herbivores. A parasite is an organism that lives on or in another organism and gets its nutrients from it. Parasitic plants get their nutrients from other plants, called host plants. Dodder, native to tropical and temperate climates around the world, is a parasitic vine that wraps around a host plant. Dodder has rootlike parts called haustoria that attach to the host plant, so it can feed on its nutrients. Eventually, the parasitic dodder feeds on all the nutrients of the host plant, and the host plant dies. The dodder vines then move on to another plant.


Herbivores in the Food Chain

Many herbivores spend a large part of their life eating. Elephants need to eat about 130 kilograms (300 pounds) of food a day. It takes a long time to eat that much leaves and grass, so elephants sometimes eat for 18 hours a day.

Herbivores depend on plants for their survival. If the plant population declines, herbivores cannot get enough food. Beavers, for example, feed on trees and plants that live near water. If the trees are removed to build houses and roads, the beaver population cannot survive.

Similarly, many carnivores need herbivores to survive. Herbivorous zebras and gazelles once traveled in great herds across the savannas of Africa. But these herds have shrunk and are now mostly confined to parks and wildlife reserves. As the number of these herbivores declines, carnivores such as African wild dogs, which prey on them, also decline. Scientists estimate that only 3,000 to 5,500 African wild dogs remain in the wild.

In some places, the disappearance of large carnivores has led to an overpopulation of herbivores. Wolves and cougars are traditional predators, or hunters, of white-tailed deer, which are herbivores. Hunting and expanding human settlements have practically eliminated these predators from the northeastern United States. Without its natural predators, the population of white-tailed deer has skyrocketed. In some areas, there are so many deer that they cannot find enough food. They now frequently stray into towns and suburbs in search of food.

Vocabulary

Term Part of Speech Definition Encyclopedic Entry

African wild dog

Noun

medium-sized animal (mammal) native to Africa.

algae

Plural Noun

(singular: alga) diverse group of aquatic organisms, the largest of which are seaweeds.

aphid

Noun

tiny insect that eats the sap of plants.

Asian long-horned beetle

Noun

large insect that feeds on the interior wood of trees, native to eastern Asia.

autotroph

Noun

organism that can produce its own food and nutrients from chemicals in the atmosphere, usually through photosynthesis or chemosynthesis.

Encyclopedic Entry: autotroph

bacteria

Plural Noun

(singular: bacterium) single-celled organisms found in every ecosystem on Earth.

carnivore

Noun

organism that eats meat.

Encyclopedic Entry: carnivore

caterpillar

Noun

larva of a butterfly or moth.

cell wall

Noun

tough, rigid, and non-living barrier surrounding the soft cells of most autotrophs, such as plants.

chamber

Noun

sealed compartment.

climate

Noun

all weather conditions for a given location over a period of time.

Encyclopedic Entry: climate

confine

Verb

to limit or enclose.

consume

Verb

to use up.

consumer

Noun

organism on the food chain that depends on autotrophs (producers) or other consumers for food, nutrition, and energy.

cougar

Noun

large cat native to the Americas. Also called puma, mountain lion, and panther.

cud

Noun

partly digested food that is regurgitated by ruminants, to chew and swallow again.

detritivore

Noun

organism that consumes dead plant material.

digest

Verb

to convert food into nutrients that can be absorbed.

dodder

Noun

parasitic plant with long, vine-like stems that take over the host plant and steal its nutrients.

earthworm

Noun

worm that lives in soil or earth.

ecosystem

Noun

community and interactions of living and nonliving things in an area.

Encyclopedic Entry: ecosystem

elephant

Noun

large mammal with a long trunk, native to Africa and Asia.

eliminate

Verb

to remove.

eucalyptus

Noun

tree native to Oceania.

fiber

Noun

long, thin, threadlike material produced by plants that aids digestive motion when consumed.

folivore

Noun

herbivore that eats mainly leaves.

food web

Noun

all related food chains in an ecosystem. Also called a food cycle.

Encyclopedic Entry: food web

frugivore

Noun

herbivore that eats mainly fruits.

fungi

Plural Noun

(singular: fungus) organisms that survive by decomposing and absorbing nutrients in organic material such as soil or dead organisms.

gazelle

Noun

small antelope native to Africa and Asia.

grasshopper

Noun

insect with large hind legs used for jumping.

haustoria

Plural Noun

(haustorium) thin, tubular feeding organs of some parasites.

herbivore

Noun

organism that eats mainly plants.

Encyclopedic Entry: herbivore

herd

Noun

group of animals.

honeybee

Noun

insect that, in a hive with other honeybees, produces honey.

host

Noun

organism that is home to a parasite.

insect

Noun

type of animal that breathes air and has a body divided into three segments, with six legs and usually wings.

koala

Noun

medium-sized animal (marsupial) that lives almost entirely in eucalyptus trees, native to Australia.

larva

Noun

a new or immature insect or other type of invertebrate.

laurel

Noun

evergreen tree with large leaves, often used as a spice called bay.

molar

Noun

large, flat tooth used for chewing and grinding.

nectar

Noun

sweet plant material that attracts pollinators.

nutrient

Noun

substance an organism needs for energy, growth, and life.

Encyclopedic Entry: nutrient

oilbird

Noun

medium-sized, nocturnal bird native to South America.

omnivore

Noun

organism that eats a variety of organisms, including plants, animals, and fungi.

Encyclopedic Entry: omnivore

organism

Noun

living or once-living thing.

overpopulation

Noun

situation where the amount of organisms in an area is too large for the ecosystem to support.

palm

Noun

type of tree with a tall trunk, no branches, and a leafy crown.

parasite

Noun

organism that lives and feeds on another organism.

park

Noun

area of land set aside for recreational use.

plant

Noun

organism that produces its own food through photosynthesis and whose cells have walls.

pollen

Noun

powdery material produced by plants.

predator

Noun

animal that hunts other animals for food.

prey

Noun

animal that is hunted and eaten by other animals.

primary consumer

Noun

organism that eats plants or other autotrophs.

producer

Noun

organism on the food chain that can produce its own energy and nutrients. Also called an autotroph.

regurgitate

Verb

to vomit or throw up undigested or partly digested food.

root

Noun

part of a plant that secures it in the soil, obtains water and nutrients, and often stores food made by leaves.

root weevil

Noun

small insect that feeds on the roots of a plant.

ruminant

Noun

type of herbivorous animal (mammal) with a specialized stomach for digesting plant material.

sap

Noun

fluid that distributes nutrients throughout a plant.

savanna

Noun

type of tropical grassland with scattered trees.

secondary consumer

Noun

organism that eats meat.

skyrocket

Verb

to increase rapidly.

soil

Noun

top layer of the Earth's surface where plants can grow.

stomach

Noun

organ in animals that helps digest food.

suburb

Noun

geographic area, mostly residential, just outside the borders of an urban area.

temperate

Adjective

moderate.

termite

Noun

small insect that feeds on wood.

trophic level

Noun

one of three positions on the food chain: autotrophs (first), herbivores (second), and carnivores and omnivores (third).

tropical

Adjective

existing in the tropics, the latitudes between the Tropic of Cancer in the north and the Tropic of Capricorn in the south.

vine

Noun

plant with a long, narrow stem that can wrap around an object or trail along the ground.

white-tailed deer

Noun

medium-sized deer (mammal) native to the Americas.

wildlife reserve

Noun

area set aside and protected by the government or other organization to maintain wildlife habitat. Also called a nature preserve.

wolf

Noun

mammal related to the dog.

xylophage

Noun

organism that consumes wood.

zebra

Noun

mammal, related to a horse, native to Africa.


For Further Exploration

Websites

Credits

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Writers

Kim Rutledge
Melissa McDaniel
Diane Boudreau
Tara Ramroop
Santani Teng
Erin Sprout
Hilary Costa
Hilary Hall
Jeff Hunt

Illustrators

Tim Gunther
Mary Crooks, National Geographic Society

Editors

Kara West
Jeannie Evers

Educator Reviewer

Nancy Wynne

Producer

Caryl-Sue, National Geographic Society

Sources

Dunn, Margery G. (Editor). (1989, 1993). "Exploring Your World: The Adventure of Geography." Washington, D.C.: National Geographic Society.

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