Yellow-backed duiker
These forest dwelling antelope feed selectively on plants or plant parts such as shoots, roots, leaves, and buds, but their diet is mainly made up of fruits. The yellow-backed duiker is more efficient at digesting poor quality food than most other duiker species. This allows them to eat large, low quality fruits. Their diet makes them very hard to keep in captivity as most domesticated fruits are not well suited to their low fiber requirements. They are considered concentrate selectors, meaning they eat "diets relatively low in fiber, have a well developed ability to forage selectively, a rumen bypass, a rapid passage and high fermentation rate for starch, and they frequently encounter toxins."
Anteater
Anteaters are specialized to feed on small insects, with each anteater species having its own insect preferences: small species are specialized on arboreal insects living on small branches, while large species can penetrate the hard covering of the nests of terrestrial insects. To avoid the jaws, sting, and other defences of the invertebrates, anteaters have adopted the feeding strategy of licking up large numbers of ants and termites as quickly as possible — an anteater normally spends about a minute at a nest before moving on to another — and a giant anteater has to visit up to 200 nests per hour to consume the thousands of insects it needs to satisfy its caloric requirements.