List of herbivorous animals

This is a list of herbivorous animals, organized in a roughly taxonomic manner. In general, entries consist of animal species known with good certainty to be overwhelmingly herbivorous, as well as genera and families which contain a preponderance of such species.
Herbivorous animals are heterotrophs, meaning that they consume other organisms for sustenance. The organisms which herbivores consume are primary producers, predominantly plants (including algae). Herbivores which consume land plants may eat any or all of the fruit, leaves, sap, nectar, pollen, flowers, bark, cambium, underground storage organs like roots, tubers, and rhizomes, nuts, seeds, shoots, and other parts of plants; they frequently specialize in one or a few of these parts, though many herbivores also have quite diverse diets.
Animal diets are not inflexible, and most animals will stray from their typical diet on occasion; for instance, cattle will eat chicks, and crocodiles will consume fruit. Though it can be hard to determine what is a true aberration, as opposed to being a normal, but minor component of the diet, animals are still regarded as herbivores, carnivores, or otherwise as long as the vast majority of their diet reflects such a categorization. Thus, several of the animals which appear on this list are commonly described as omnivores, but, where consumption of animal matter is marginal, they meet the criteria for inclusion. These cases are elaborated upon within the article.
Where quantifiable data to support such an evaluation exist, this list generally includes animals whose diets are at least ~90% herbivorous, as a simple and arbitrary minimum, though a great many listees are far more herbivorous than this; perhaps the majority are closer to 95%, and a large number are nearly purely herbivorous. However, a small selection of taxa which are not usually this herbivorous also receive mention; typically, this is done when the animal is much more herbivorous than the vast majority of close relatives. For example, the maned wolf receives mention; its diet varies from mostly carnivorous to overwhelmingly frugivorous, being mostly a fairly balanced omnivore overall, but they are still listed because no other living Canid is nearly so herbivorous. Other animals may receive mention if at least some populations of the species regularly consume very plant-heavy diets.
The issue is further complicated by variation based on region, sex, age, season, and other factors, as well as differing techniques for measuring dietary proportions and a lack of data on many species. A number of listed taxa also consume a significant quantity of fungi. On the whole, however, this list consists almost entirely of animals which are known with good certainty to be overwhelmingly herbivorous, with exceptions being noted.
Herbivory is of extreme ecological importance and prevalence among insects. Perhaps one third (or 500,000) of all described species are herbivores. Herbivorous insects are by far the most important animal pollinators, and constitute significant prey items for predatory animals, as well as acting as major parasites and predators of plants; parasitic species often induce the formation of galls. Herbivorous insects also form symbioses with numerous plants, animals, and fungi, including complex relationships with various species of ant, and have greatly impacted the evolution of plants.
Herbivorous fish play a key role in maintaining healthy ecosystems, especially in tropical reefs, where they promote a balance between corals and macroalgae. Herbivorous fish include:
Unusually for tetrapods, herbivory is rare among extant adult lissamphibians. There are, however, many larval and a few adult amphibians which take significant plant matter:
All snakes and the majority of non-snake squamates (lizards) are carnivorous. However, some degree of herbivory is relatively common among lizards. Perhaps 12% of lizards have diets which are >10% herbivorous. Dedicated herbivory, with plants constituting >90% of the diet, occurs in perhaps ~1% of lizards, though estimates vary.
Although, by some counts, only 2-3% of extant bird species are primarily herbivorous, herbivorous birds are nonetheless incredibly diverse, having evolved independently within at least nine distinct lineages. Herbivorous birds include important pollinators and seed dispersers, as well as both the smallest and largest living birds (the bee hummingbird and the common ostrich, respectively). On islands with little to no mammalian colonization, large herbivorous birds frequently evolved to assume niches typically held by mammals, sometimes attaining enormous sizes; on the Hawaiian Islands, New Zealand, Madagascar, Mauritius, New Caledonia, and Fiji, birds were nearly if not the largest terrestrial herbivores, though the vast majority are now extinct. Birds which are mostly herbivorous as adults will frequently feed their young a far more insectivorous diet, though there are many exceptions.
Herbivory is quite common among mammals, with herbivores occurring across diverse lineages and in a large variety of sizes, bodyplans, and niches. Both large and small herbivorous mammals are often important prey species for various predators, though the largest, such as the so-called "pachyderms", are generally safe from predation as healthy adults. Large, herbivorous mammals came to dominate global ecosystems in the Cenozoic, and, though vastly reduced in number, they continue to be key features of certain modern ecosystems, such as the Maasai Mara and Kaziranga National Park.