Basic Information
A herbivore is an animal whose natural diet consists predominately of plants (some zoologists allow any unresisting diet, so including fungi and various microorganisms such as plankton). Such animals are also termed "primary consumers" and tend to form the second tier of a trophic pyramid (i.e. the one directly after the "producers"). Some herbivores can also consume animal material, others cannot, but any species for which other animals are a meaningful part of a natural diet is generally termed an omnivore.
By their nature herbivores tend to serve as prey species, subject to consumption by those at higher trophic levels and have a variety of adaptations to account for this, ranging from fast escape to heavy protection, with exact methods depending on circumstances and the specific nature of their diet.