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Many animals are either herbivores, who eat only plant food, or carnivores, who eat only the flesh of other animals. The preference for one type of food or the other depends largely on the type of digestive system that the animal has, and the resources it can put into its “energy budget.” Meat is generally easier to digest and requires a less complex digestive system and a relatively short intestinal tract. However, in order to get meat, carnivores have to invest a lot of time hunting their prey, and the outcome of a hunt is always uncertain. The food of herbivores ismucheasier to obtain, since plants do not move and all the herbivore has to do is graze on the grasses, leaves, or algae readily available around it. However, the cellulose that plants are made of is very tough to digest, and thus herbivores must have a much more complex and lengthy digestive tract than carnivores. Many herbivores are ruminants, with multipart stomachs, who have to chew and digest their food more than once in order to get adequate nutrition from it. Carnivores and herbivores are also vulnerable to a loss of their food source. Herbivores whose digestive systems are specialized to process only one type of food will starve if that food becomes scarce due to drought or some other climatic change. Carnivores often have specialized hunting patterns that cannot be changed if the prey (usually herbivores) become scarce due to loss of their own food source. Omnivores maximize their ability to obtain food by having digestive tracts capable of processing both plant and animal food, although they are usually not capable of digesting the very tough plant material, such as grasses and leaves, that many large herbivores eat. Omnivores may also be scavengers, eating whatever carrion they may come across. Omnivores often lack the specialized food-gathering ability characteristic of pure carnivores and herbivores. Many animals often thought of as carnivores are actually omnivores, eating both plants and animals.

Types of Omnivores
Omnivores can be found among all types of animals, living on land and in water. They include fishes, mollusks, arthropods, birds, and mammals. Most insects are either herbivores, such as grasshoppers, or carnivores such as mantises. However some, such as yellow jacket wasps, are omnivores, eating other insects, fruit, and nectar. Omnivorous snails and slugs eat algae, leaves, lichens, insects, and decaying plant and animal matter. Their main organ for eating is called a radula, a tonguelike, toothed organ that is drawn along rocks, leaves, or plants to scrape off food; it is also used to bore holes through shells of other mollusks, to get to their flesh. Omnivorous fish include the common carp, goldfish, catfish, eels, and minnows. Since a fish’s food is often suspended in the medium through which the fish swims—water—being able to gulp up whatever comes into its mouth is an efficient way for a fish to eat. Similarly, bottom-feeders (fish that suck up material from the floor of whatever body of water they inhabit) also benefit from not needing to sort through the material before they ingest it. Many birds are omnivores, such as robins, ostriches, and flamingos. The pink or red color of flamingos occurs because they eat blue-green algae and higher plants which contain the same substances that make tomatoes red. They also eat shrimp and small mollusks. Mammal omnivores include bears, members of the weasel family, such as skunks, the raccoon family (raccoons and coatimundis), monkeys, apes, and humans. Raccoons and coatis, found only in the Americas, eat insects, crayfish, crabs, fishes, amphibians, birds, small mammals, nuts, fruits, roots, and plants. Like other omnivores, they also eat carrion. Bears eat grass, roots, fruits, insects, fishes, small or large mammals, and carrion.

Some interesting facts about Omnivore:

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Principal Terms

carnivore: a flesh-eating animal
carrion: dead animals
diurnal: active during the day
herbivore: an animal that eats only plants
hermaphrodite: an organism having male and female reproductive systems
radula: a tonguelike, toothed organ for grinding food

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