Animals are heterotrophs. Heterotrophs can be herbivores (feed on plants), carnivores (feed on animals) or omnivores (feed on both plants and animals).

The mode of nutrition for animals also depends on the availability of food.

For example, elephants are mostly herbivores, but can be carnivores, if suitable food is available.

And Tigers are carnivores, but adapt to being herbivores when their suitable food is unavailable.