The horn of the rhinoceros is made of keratin, the same protein found in human hair and fingernails. It is divided into two parts: a solid core called the horn core and a hard, fibrous outer shell called the horn sheath. The horn core is attached to the skull of the rhinoceros and grows continually throughout the animal's life. The horn sheath is worn down by rubbing against vegetation and other objects in the environment.
Rhinoceros horns come in a variety of shapes, depending on the species. Some are long and straight, while others are short and curved. Some horns are round in cross-section, while others are oval or triangular. The size and shape of the horns can vary even within the same species, depending on the individual animal.
Here is a more detailed description of the horn shape of each rhinoceros species:
Black rhinoceros: The horn of the black rhinoceros is long and straight. The front horn is typically longer than the rear horn. In males, the horns can reach a length of up to 1.4 meters (4.6 feet). In females, the horns are usually shorter, reaching a length of up to 1.1 meters (3.6 feet).
White rhinoceros: The horn of the white rhinoceros is long and straight. The front horn is slightly shorter than the rear horn. In males, the horns can reach a length of up to 1.8 meters (5.9 feet). In females, the horns are shorter, reaching a length of up to 1.5 meters (4.9 feet).
Greater one-horned rhinoceros: The horn of the greater one-horned rhinoceros is long and straight. In males, the horn is typically longer than in females. In males, the horns can reach a length of up to 1.5 meters (4.9 feet). In females, the horns are shorter, reaching a length of up to 90 centimeters (3 feet).
Sumatran rhinoceros: The horn of the Sumatran rhinoceros is short and curved. In males, the horns can reach a length of up to 80 centimeters (32 inches). In females, the horns are shorter, reaching a length of up to 35 centimeters (14 inches).
Javan rhinoceros: The horn of the Javan rhinoceros is short and slightly curved. In males, the horns can reach a length of up to 100 centimeters (40 inches). In females, the horns are shorter, reaching a length of up to 50 centimeters (20 inches).