What protein makes up the horns of African rhinoceroses?

African rhinoceros horns are made primarily of keratin.

Keratin is a tough structural protein also found in human hair and fingernails, as well as in the claws, hooves and feathers of many animals. Unlike antelope horns, a rhinoceros horn does not have a bony core covered by a permanent keratin sheath. It is a compact mass of keratin fibres that grows from the skin.

Both African rhinoceros species have two horns: the black rhinoceros and the white rhinoceros. The front horn is usually longer than the rear horn. Horn shape and size vary among individuals, and the horn can regrow gradually if part of it is damaged or removed.

The mistaken belief that rhino horn is a medicinal substance has helped drive illegal poaching. Scientific analysis finds no special curative property; chemically, it is comparable to other keratin-based tissues. Conservation programmes therefore focus on habitat protection, anti-poaching work and demand reduction.