Herbivores are animals that exist mainly on a diet of plants or algae. Some eat a wide range of plants, others are more exclusive and eat only particular types, such as monarch butterfly caterpillars which feed on milkweed and pandas on bamboo. Anatomical and physiological adaptations help some herbivores become specialists, for example, in their tolerance of spiky leaves or an in-built antidote to toxins. Other specialists restrict themselves to certain parts of a plant: hummingbirds feed on nectar and greenfly feed on sap.

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