The Unicorn's horn is from the Rhinoceros, "most formidible beast in the world," his horn a symbol of power: "And who would cross Tom Rhinoceros does what the panther dares not." In the first Century A.D., rhinohorns were hard to obtain and traders fraudulently substituted the Narwhal horn, which became an acceptable equivalent "because of its white color and superior hardness and because it is curved in the spiral of immortality, and because the variously named God if the Year always came out of the sea." The Unicorn is usually pictured with a horn resembling the narwhal's more than the rhinoceros, probably because almost all surviving Unicorn and because the Unicorn-drawings are comparatively recent.

There are five species of rhinos two African and three Asian. The African species are the white and black rhinos. Both species have two horns. Asian rhinos include the Indian and the Javan, each with one horn, and the Sumatran, which has two. The white rhino is the second largest land mammal next to the elephant. The five species range in weight from 750 pounds to 8,000 pounds and stand anywhere from four and a half to six feet tall.
Rhinos are herbivores, meaning they eat only plants. White rhinos, with their square-shaped lips, are ideally suited to graze on grass. Other rhinos prefer to eat the foliage of trees or bushes.
As solitary creatures, both male and female rhinos establish territories. Males mark and defend their territories. Rhinos use their horns not only in battles for territory or females but also to defend themselves from lions, tigers and hyenas.
Males and females frequently fight during courtship, sometimes leading to serious wounds inflicted by their horns. After mating, the pair go their separate ways. A calf is born 14 to 18 months later. Although they nurse for a year, calves are able to begin eating vegetation one week after birth.
Rhinos rank among the most endangered species on Earth. Valued for their horns, they face a serious threat from poaching. Some cultures believe that the powdered rhino horn will cure everything from fever to food poisoning and will enhance sexual stamina.