Grown rhinos do not have any natural predators, except humans. The sad truth is that the critical situation of the rhinoceroses’ populations is 100% man-made. The main reason that rhinoceros are endangered is the poaching for their horns. In many Asian countries, it is still believed that rhino horn is a cure for cancer and can also be used as an aphrodisiac.
This is based on Traditional Chinese Medicine (TCM) and even though many TCM educators speak out against using rhino horn for medical reasons, many people still believe in its healing powers. In fact, rhino horn consists of keratin, the same protein that hair and fingernails are made of, so it is scientifically proven that there is no healing effect whatsoever.
Still, the demand for rhino horn is very high. On the international black market, rhino horn costs the same per weight as gold. It's not surprising that illegal poaching continues in Asia and Africa and gets harder and harder to control.