Living Garbage Cans
Some animals, such as tiger sharks or goats, have been known to consume a wide variety of objects: aluminum cans, surfboards, clothes and textiles, plastics, and rope. These "living garbage cans" are not considered omnivores, because they gain no nutritional value or energy from these products. Tiger sharks are carnivores that mistake these items for food. Goats are herbivores that are curious about unique odors or new foods.
An omnivore is an organism that regularly consumes a variety of material, including plants, animals, algae, and fungi. They range in size from tiny insects like ants to large creatures—like people.
Human beings are omnivores. People eat plants, such as vegetables and fruits. We eat animals, cooked as meat or used for products like milk or eggs. We eat fungi such as mushrooms. We also eat algae, in the form of edible seaweeds such as nori, which are used to wrap sushi rolls, and sea lettuce, eaten in salads. Bears are omnivores, too. They eat plants like berries as well as mushroom fungi and animals like salmon or deer.
Omnivores are a major part of the food web, a description of which organisms eat which 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, organisms that consume plants and other autotrophs, are the second trophic level. Both omnivores and carnivores, meat eaters, 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.
Most birds are omnivores. Robins pull worms from the ground. They also feast on berries. Ostriches graze on plants and grasses. They also eat lizards and insects.
Many mammals are omnivorous. Skunks eat rodents, lizards, honeybees, leaves, grasses, nuts, fungi, and almost anything else they can find.
Some reptiles are also omnivorous. Box turtles feed on fish, frogs, rodents, and many other creatures, but they also eat flowers, berries, and roots.
Fish can also be omnivorous. The opaleye, a fish that feeds mostly on seaweeds along the Pacific Coast of North America, also eats small creatures found among the seaweed.
Some insects are omnivores. Ants eat seeds, nectar, and, often, other insects.
Some omnivores are scavengers, creatures that eat the meat of dead animals. Black bears eat mostly nuts, berries, and other fruit. But if they find a dead animal, they eat it.
Many animals that are often thought of as carnivores are in fact omnivores. Red foxes, for example, prey on rabbits, but they also eat fruit.
Some animals that are thought of as herbivores also eat animals. Squirrels eat mostly nuts, fruits, and seeds, but they sometimes eat insects, small birds, and other creatures.
Many omnivores have biological adaptations that help them eat a variety of kinds of foods. They have adapted many characteristics of both carnivores and herbivores. Like many carnivores, raccoons have sharp front teeth that help them rip apart mice and other small creatures. And like many herbivores, raccoons also have large molars that help them chew up plants. Raccoons also have quick paws and long fingers that they can use both to grab prey and to reach a variety of fruits and other plant products.
Compared to herbivores and carnivores, omnivores often have a greater chance of surviving difficult conditions. They can adjust their diets. If all the salmon or other animals disappear from a river ecosystem, a big cat living in that habitat could not survive. Cats are carnivores that cannot digest or obtain nutrients from plant material. However, a grizzly bear could still survive eating berries, fruit, roots, and insects.
Because they have an easier time finding food, omnivores are sometimes better at adapting to new environments than creatures with more specific feeding habits. Omnivores can better adapt to development than herbivores or carnivores.
Urban development, the process of clearing land for homes, business, and agriculture, destroys habitats, the places where animals live in the wild. Herbivores such as elephants cannot survive without a lot of trees and grasses to eat. But omnivores such as opossums, seagulls, and many species of monkey easily adapt to life in urban areas and farmland, where they often find meals in garbage cans.
Term Part of Speech Definition Encyclopedic Entry agriculture Noun
the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).
Encyclopedic Entry: agriculture algae Plural Noun
(singular: alga) diverse group of aquatic organisms, the largest of which are seaweeds.
organism that can produce its own food and nutrients from chemicals in the atmosphere, usually through photosynthesis or chemosynthesis.
Encyclopedic Entry: autotroph big cat Noun
large predators, including tigers, lions, jaguars, and leopards.
biological adaptation Noun
physical change in an organism that results over time in reaction to its environment.
box turtle Noun
small reptile with a tall, domed shell.
organism that eats meat.
Encyclopedic Entry: carnivore characteristic Noun
physical, cultural, or psychological feature of an organism, place, or object.
person who uses a good or service.
to reduce or go down in number.
growth, or changing from one condition to another.
Encyclopedic Entry: development diet Noun
foods eaten by a specific group of people or other organisms.
Encyclopedic Entry: diet digest Verb
to convert food into nutrients that can be absorbed.
community and interactions of living and nonliving things in an area.
Encyclopedic Entry: ecosystem farmland Noun
area used for agriculture.
food chain Noun
group of organisms linked in order of the food they eat, from producers to consumers, and from prey, predators, scavengers, and decomposers.
Encyclopedic Entry: food chain food web Noun
all related food chains in an ecosystem. Also called a food cycle.
Encyclopedic Entry: food web fruit Noun
edible part of a plant that grows from a flower.
fungi Plural Noun
(singular: fungus) organisms that survive by decomposing and absorbing nutrients in organic material such as soil or dead organisms.
grizzly bear Noun
large mammal native to North America.
environment where an organism lives throughout the year or for shorter periods of time.
Encyclopedic Entry: habitat herbivore Noun
organism that eats mainly plants.
Encyclopedic Entry: herbivore insect Noun
type of animal that breathes air and has a body divided into three segments, with six legs and usually wings.
animal with hair that gives birth to live offspring. Female mammals produce milk to feed their offspring.
animal flesh eaten as food.
large, flat tooth used for chewing and grinding.
mammal considered to be highly intelligent, with four limbs and, usually, a tail.
fungus, usually with an umbrella-shaped cap on top of a slender stalk.
sweet plant material that attracts pollinators.
red algae that is often dried and used to wrap sushi.
substance an organism needs for energy, growth, and life.
Encyclopedic Entry: nutrient omnivore Noun
organism that eats a variety of organisms, including plants, animals, and fungi.
Encyclopedic Entry: omnivore opaleye Noun
medium-sized fish native to the Pacific Ocean.
living or once-living thing.
very large, flightless bird native to Africa.
organism that produces its own food through photosynthesis and whose cells have walls.
animal that is hunted and eaten by other animals.
primary consumer Noun
organism that eats plants or other autotrophs.
organism on the food chain that can produce its own energy and nutrients. Also called an autotroph.
animal that breathes air and usually has scales.
small bird native to Europe.
order of mammals often characterized by long teeth for gnawing and nibbling.
part of a plant that secures it in the soil, obtains water and nutrients, and often stores food made by leaves.
organism that eats dead or rotting biomass, such as animal flesh or plant material.
Encyclopedic Entry: scavenger sea lettuce Noun
seaweed with large, flat leaves.
marine algae. Seaweed can be composed of brown, green, or red algae, as well as "blue-green algae," which is actually bacteria.
secondary consumer Noun
organism that eats meat.
exact or precise.
bite-sized rolls or balls of sticky rice topped with seafood or vegetables.
small monkey native to Central and South America.
trophic level Noun
one of three positions on the food chain: autotrophs (first), herbivores (second), and carnivores and omnivores (third).
urban area Noun
developed, densely populated area where most inhabitants have nonagricultural jobs.
Encyclopedic Entry: urban area vegetable Noun
plant that is grown or harvested for food.