Many types of animals are omnivorous, including birds, mammals and primates. Omnivores subsist on a variety of food sources, including both plant and animal-based items.
Many animals of the desert are omnivores. This may occur because food is difficult to find in the desert, so animals living there cannot be very picky. Desert shrimp, which live in the temporary pools of the desert, are omnivorous crustaceans that subsist on a variety of tiny organic particles. Many omnivores of the desert derive the moisture they need from their food sources.
While food is more plentiful in forests and fields, omnivores inhabit these environments as well. Many insects are omnivorous, including flies, wasps and roaches. Chickens, turkeys and their relatives subsist on insects, small vertebrates, acorns and small seeds. Other birds like crows and ravens are very successful omnivores that may eat berries, insects, rodents or carrion.
Pigs are omnivores; while they primarily root in the mud and dirt for tubers, they often eat grubs and other insects. Wetlands contain numerous omnivorous species as well, such as raccoons and opossums. While adult frogs are universally carnivorous, many tadpoles survive by eating algae.
Many extinct animals including dinosaurs are also believed to have been omnivores.