Rhinoceros are herbivores, and their lip shape is influenced by the types of low-lying grasses, leaves and branches they eat, according to National Geographic. For example, African black rhinos have a slightly pointed upper lip that hooks downward, letting them grab plants and fruit from bushes and trees. African white rhinos have flatter, broad lips made for grazing on low ground.

Rhinos are highly endangered, and only five species exist internationally. The previously mentioned African varieties typically inhabit floodplains and grasslands, while the Javan, Sumatran and greater one-horned rhinos of Asia wallow in rain forests and swampy areas. The greater one-horned rhino uses grazing and foraging techniques to find food, so its lip shape is both broad and hooked. Rhinos also use their horns to snap branches and pull up tough roots for easier consumption.

Rhinos are not naturally aggressive toward other animals and don't hunt for meat, but their strong horns help fight off potential attackers, especially when their calves are threatened. While physically powerful, rhinos have weak eyesight and often rely on their sharp hearing to assess danger. Female calves are charged with protecting their young from crocodiles, big cats and other adult rhinos. Humans are considered the greatest threat to full-grown rhinos because their valuable horns are collected for medicinal and ornamental purposes.