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Many different animal species feed on plants. They are often called herbivores, which is the general term for creatures that eat plants and plant-like organisms. But we can get more specific. Biologists classify herbivores according to what parts of a plant the animals consume:

  • graminivores eat seeds (example: mice)
  • folivores...

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Many different animal species feed on plants. They are often called herbivores, which is the general term for creatures that eat plants and plant-like organisms. But we can get more specific. Biologists classify herbivores according to what parts of a plant the animals consume:

  • graminivores eat seeds (example: mice)
  • folivores eat leaves (examples: caterpillars, howler monkeys)
  • gumnivores eat plant gum exudates (example: marmosets)
  • xylophages eat wood (example: termites)
  • nectivores eat nectar (examples: bees and hummingbirds)
  • frugivores eat fruit (example: orangutans)

Are these creatures "predators" of the plants? It depends on your definition, and on how plants are affected by the animals that eat them.

Researchers sometimes refer to plant-eaters as predators (for an example, see the scientific paper in the last link below). The terminology is useful when the relationship between herbivore and plant is similar to that of a predator and its animal prey: The eater seeks out the eaten, and the interaction is antagonistic. In such cases, we can see many parallels between animal prey and plant prey.

For instance, like animal prey species, plant prey species have evolved adaptations to defend themselves against predators. These adaptations include

  • chemical defenses, like secondary compounds that make plant tissues toxic or difficult to digest, and
  • mechanical defenses, like spines, thorns, barbs, and hard casings.

In response, plant predators have evolved their own adaptations to overcome these defenses. For example, eucalyptus leaves contain secondary compounds that deter most would-be predators. But the koala, which specializes in eating eucalyptus, has evolved the ability to detoxify and metabolize those compounds. The competing interests of predators and prey can lead to an evolutionary arms race, in which a plant evolves ever-stronger defenses, and a predator evolves ever–more effective counter strategies.

However, not all cases of plant-eating are antagonistic to the plant. A good example is a hummingbird drinking nectar. The plant benefits because the hummingbird helps pollinate the plant. Similarly, an orangutan that digests the flesh of a fruit but spits out or excretes the seeds can help a tree spread its offspring to distant parts of a forest. In these cases, the relationship is mutualistic -- both sides benefit. So the animals would not be considered predators.

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