La stessa ragione per cui si mangiano varie cose. O ti aiutano o sono piacevoli da consumare.

Anche i carnivori obbligati come i gatti mangiano a volte non carne, come l'erba. Non possono digerirla bene, ma ricevono qualche beneficio o non lo farebbero.

Crescendo, le nostre anatre da compagnia passavano ore a masticare un topo morto finché uno di loro poteva ingoiarlo intero. I nostri polli domestici pulivano la carcassa del tacchino del giorno del ringraziamento fino all'osso.

A loro piace o ne hanno bisogno.

There’s two kinds of omnivores.

1. Biological omnivores where they are biologically designed to be omnivores that can get optimal nutrition from a variety of sources both plant and animal based.
2. Behavioral omnivores where the creature is biologically designed to eat a specific type of food, such as a carnivore or an herbivore, but occasionally makes a snack out of something outside it’s natural food source.

The first kind is designed to be omnivorous, they have adaptions that mean they do well eating multiple types of foods. The second kind is only adapted to eating a certain kind of food and gets little if any value from omnivorous behavior. Although it should be noted that herbivores that practice behavioral omnivory can get a little more benefit from it than carnivores because a longer, more specialized digestive system is required to digest plant matter properly and biological carnivores have the shortest digestive tracts.