Omnivore () is a consumption classification for animals that have the capability to obtain chemical energy and from materials originating from plant and animal origin. Often, omnivores also have the ability to incorporate food sources such as algae, Fungus, and bacteria into their diet as well.
Omnivores come from diverse backgrounds that often independently evolved sophisticated consumption capabilities. For instance, dogs evolved from primarily carnivorous organisms (Carnivora) while pigs evolved from primarily herbivorous organisms (Artiodactyla). What this means is that physical characteristics are often not reliable indicators of whether an animal has the ability to obtain energy and nutrients from both plant and animal matter. Owing to the wide range of entirely unrelated organisms independently evolving the capability to obtain energy and nutrients from both plant and animal materials, no generalizations about the anatomical features of all omnivores can realistically be made.
The variety of different animals that are classified as omnivores can be placed into further categories depending on their feeding behaviors. include Maned wolf and ; include and pink fairy armadillos; Seed predation include Finch and . (This is due to the average human diet mainly consisting of , with rice, maize and wheat comprising two-thirds of human food consumption).
All of these animals are omnivores, yet still fall into special niches in terms of feeding behavior and preferred foods. Being omnivores gives these animals more food security in stressful times or makes possible living in less consistent environments.
Occasionally, it is found that animals historically classified as carnivorous may deliberately eat plant material. For example, in 2013, it was considered that American alligators ( Alligator mississippiensis) may be physiologically omnivorous once investigations had been conducted on why they occasionally eat fruits. It was suggested that alligators probably ate fruits both accidentally but also deliberately.
"Life-history omnivores" is a specialized classification given to organisms that change their eating habits during their life cycle. Some species, such as grazing waterfowl like geese, are known to eat mainly animal tissue at one stage of their lives, but plant matter at another.Maclean, Gordon Lindsay (1993). Roberts' Birds of Southern Africa. Publisher: New Holland. . The same is true for many insects, such as beetles in the family Meloidae,Skaife, S. H. (1953). African Insect Life. Pub. Longmans, Green & Co., London. which begin by eating animal tissue as , but change to eating plant matter after they mature. Likewise, many mosquito species in early life eat plants or assorted detritus, but as they mature, males continue to eat plant matter and nectar whereas the females (such as those of Anopheles, Aedes and Culex) also eat blood to reproduce effectively.
but individual diets can range from almost exclusively herbivorous to almost exclusively carnivorous, depending on what food sources are available locally and seasonally. are classified as carnivores, both taxonomically (they are in the Taxonomic rank Carnivora), and behaviorally (they subsist on a largely carnivorous diet). Depending on the species of bear, there is generally a preference for one class of food, as plants and animals are digested differently. Wolf subspecies (including wolves, , , and ) have a general preference and are evolutionarily geared towards meat, but also will voluntarily eat plant material like fruits, vegetables, and grasses, and can live on such indefinitely. Also, the maned wolf is a canid whose diet is naturally 50% plant matter.
While most mammals may display "omnivorous" behavior patterns depending on conditions of supply, culture, season and so on, they will generally prefer a particular class of food, to which their digestive processes are adapted. Like most arboreal species, most squirrels are primarily granivores, subsisting on nuts and seeds.Halle, S. & Stenseth, N. (2000). Activity patterns in small mammals: an ecological approach. Berlin; Heidelberg, Germany; New York: Springer-Verlag. p. 131. But like virtually all mammals, squirrels avidly consume some animal food when it becomes available. For example, the American eastern gray squirrel has been introduced by humans to parts of Britain, continental Europe and South Africa. Where it flourishes, its effect on populations of nesting birds is often serious, largely because of consumption of eggs and nestlings.Moller, H. (1983). "Food and foraging behaviour of red ( Scirus vulgaris) and grey ( Scirus carolinensis) squirrels". Mammal Review 13: 81-98.
Quite often, mainly herbivorous creatures will eagerly eat small quantities of animal food when it becomes available. Although this is trivial most of the time, omnivorous or herbivorous birds, such as sparrows, often will feed their chicks insects while food is most needed for growth.Capinera, John (2010). Insects and Wildlife. Publisher: Wiley-Blackwell. . On close inspection it appears that nectar-feeding birds such as sunbirds rely on the ants and other insects that they find in flowers, not for a richer supply of protein, but for essential nutrients such as cyanocobalamin that are absent from nectar. Similarly, monkeys of many species eat maggoty fruit, sometimes in clear preference to sound fruit.Ewing, Jack (2005). Monkeys Are Made of Chocolate. Publisher: Pixyjack Press. . When to refer to such animals as omnivorous, or otherwise, is a question of context and emphasis, rather than of definition.