What Are Herbivores? Characteristics and Categories

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Herbivores are animals that have adapted to eat autotrophs: organisms that can produce their own food, such as through light, water, or chemicals like carbon dioxide. Autotrophs include plants, algae, and some bacteria.

Herbivores come in all shapes and sizes in the animal kingdom. They include insects and aquatic and non-aquatic vertebrates. They can be small, like a grasshopper, or large, like an elephant. Many herbivores found living in close proximity to humans, such as rodents, rabbits, cows, horses, and camels.

Herbivores are Part of a Food Web

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food chain describes the feeding relationship between different organisms, starting from the first source of food and ending with the last. For example, if a rat eats corn and an owl eats the rat, the food chain starts with an autotroph (corn) and ends with a carnivore (owl). Food chains can vary in the number of links included in the chain to show more detailed relationships between organisms.

Herbivores are eaten by carnivores (animals that eat other animals) and omnivores (animals that eat both plants and animals). They are found somewhere in the middle of the food chain.

Although food chains are useful, they can be limiting, as different animals sometimes eat the same food source. For example, a cat could also eat the rat from the example above. To describe these more complex relationships, food webs, which describe the interconnection between multiple food chains, can be used.

 

Herbivores Eat Many Different Kinds of Plants

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Herbivores differ in the types of plant matter they eat. Some herbivores eat only specific parts of a plant. For example, some aphids only feed on sap from one very specific plant. Others can eat the entire plant.

The types of plants herbivores eat varies widely. Some herbivores can eat many different plants. For instance, elephants can eat bark, fruit, and grasses. Other herbivores, however, only focus on one specific plant

Herbivores can be classified according to the types of plants they feed on. Here are some of the most common classifications:

  • Granivores eat seeds in a number of ways. Some bugs suck out the insides of seeds, and some rodents use their front teeth to gnaw at seeds. Granivores can eat seeds before they have been dispersed by the plant into the world, afterwards, or seek both kinds.
  • Grazers like cows and horses feed mainly on grasses. They have a rumen, or first stomach, which holds a large amount of food and causes food to leave the stomach slowly. This process is necessary for grass, which is high in fiber and low in nutrients. The mouths of grazers allow them to easily eat large portions of grass but make it difficult for them to eat certain parts of a plant.
  • Browsers like giraffes eat leaves, fruits, twigs, and flowers of woody plants. Their rumens are smaller and thus hold less food than grazers’. Browsers also eat a lot of easily digestible food.
  • Intermediate feeders like sheep have characteristics of both grazers and browsers. Typically, these feeders can eat selectively but still tolerate considerable amounts of fiber in their diet.
  • Frugivores prefer fruit in their diet. Frugivores can include both herbivores and omnivores, with herbivorous frugivores tending to eat the fleshy parts of fruits and the seeds of plants.

 

Herbivores Have Wide, Flat Teeth

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Herbivores evolved teeth that are specially designed to break down plants. Their teeth are often wide and flat, with broad surfaces that act to grind down the cell walls that constitute the tough, fibrous parts of plants. This helps release nutrients within the plants, which would have otherwise passed undigested through the animal’s body, and aids in digestion by increasing the surface area that is accessible by the animal’s digestive enzymes.

 

Herbivores Have a Specialized Digestive System

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Animals cannot produce their own sources of food, and instead must consume other organisms to obtain the energy they need. Herbivores, like all vertebrates, do not have the enzymes necessary to break down cellulose, a main constituent of plants, which limits them from accessing many of the nutrients they require.

The digestive systems of herbivorous mammals have to evolved to contain bacteria that break down the cellulose. Many herbivorous mammals digest plants in one of two ways: foregut or hindgut fermentation.

In foregut fermentation, bacteria process food and break it down before it is digested by the animal’s “true stomach.” Animals that use foregut fermentation have stomachs with multiple chambers, which separates bacteria from the acid-secreting part of the stomach and prolongs digestion so that the bacteria have adequate time to process the food. To help with digestion, the animal may regurgitate the food, chewing and swallowing it again. These herbivores are further classified as ruminants, after the Latin word ruminare (“to chew over again”). Animals that use foregut fermentation include cows, kangaroos, and sloths.

In hindgut fermentation, bacteria process food and break it down after it is digested, in the latter part of the gut. Animals do not regurgitate food to help with digestion. Animals that use hindgut fermentation include horses, zebras, and elephants.

Foregut fermentation is very efficient, extracting many nutrients out of food. Hindgut fermentation is a faster process, but muchless efficient, so animals that use hindgut fermentation must eat large amounts of food in a shorter time.

It should be noted that not all herbivores process food with foregut and hindgut fermentation. Some herbivores, like several types of grasshoppers, have the enzyme necessary to break down cellulose without the help of bacteria.

 

Key Takeaways

  • Herbivores are animals that have adapted to eat plants and other autotrophs – organisms that can produce their own food, such as through light, water, or chemicals like carbon dioxide.
  • The feeding relationships between herbivores can be described by food chains, or food chains linked together into a more complex food web.
  • There are many types of herbivorous animals. Herbivores can be further grouped into different classifications depending on the food they primarily eat for their diet.
  • Herbivores have evolved many features that will allow them to eat plants, including wide and flat teeth and specialized digestive systems – though the details of these adaptations vary among herbivores.

 

Sources

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