An herbivore is an animal which only eats material which is of plant origin. Many animals around the world are herbivores, ranging from microscopic sea organisms to wild elephants, and herbivores make up the bulk of the food chain. Many large herbivores are heavily relied on by humans as a source of transportation, textiles, and food. Like any animal, herbivores require a balanced diet to survive, and different herbivores are accustomed to eating different types of plants; an imbalance in this diet can be dangerous.
In many cases, an herbivore has actually specifically adapted over thousands of years to eat only plant material. Some herbivores, for example, have evolved multiple stomachs to assist with the digestion of plant material, and herbivores also have specialized teeth which are designed to help them eat the plants in their native environment. In some cases, eating meat products will actually make an herbivore extremely sick, as it lacks the digestive enzymes to handle meats. Some well known examples of herbivores are horses and deer, along with rabbits.
In other instances, an animal chooses to be largely herbivorous because this feeding habit may be more efficient than eating meat. An animal which eats both plants and other animals is known as an omnivore, from the Latin roots omne for “all” and vorare for “eats.” These animals also have unique digestive systems which are designed to cope with both animal and plant foods. Common omnivores include humans, who may elect to eat an herbivorous or vegan diet, and chickens. In some cases, an omnivore also scavenges for food, in addition to hunting or harvesting it, as in the case of rats.
The other end of the spectrum is a carnivore, an animal which eats solely or mostly meat. Some carnivores supplement their diets with small amounts of plant material, but in such trace amounts that they can be considered carnivorous. Contrary to popular belief, it is possible for many carnivores to be healthy without ever eating plant material, as long as they seek out the right meats. Big cats are well known carnivores, as are polar bears and many reptiles. Some carnivores such as vultures survive specifically on scavenged foods.
Meeting the dietary needs of an herbivore can be challenging, since these animals often require a high volume of food because plant material is difficult to digest. Some herbivores also have extremely specific diets, derived from the environments that they evolved in; koalas, for example, will sometimes only eat eucalyptus leaves. An herbivore kept in captivity must be carefully fed to ensure that it stays healthy and strong.