Easily recognized by their nose horns and thick armor-resembling
skin, rhinoceroses are familiar to wildlife enthusiasts everywhere.
Found throughout Africa and southern Asia, these massive animals are
intimidating fauna of their local environments. Of the five species
of rhinoceros, two inhabit Africa, the black rhino, and the white
rhino. The other three species, the Javan rhino, Sumatran Rhino, and
Indian rhino are found throughout southern Asia, with each species'
range encompassing the geographic location of its name.
The word rhinoceros literally means "nose horn", derived from the
Greek rhis, meaning nose, and keros, meaning horn. All rhinos have
horns, but two species, the Indian rhino and Javan rhino, have but
one horn, while the black rhino, white rhino, and Sumatran rhino
have two horns. Rhino "horns" are not true horns. True horns consist
of a bony core, covered by a keratin sheath. Rhinoceros horns are
composed of keratin, but lack a bony core. They are simply a group
of highly compacted keratin fibers on a roughened area of the skull.
Despite their horns and armored appearance, one may expect rhinos to
share close ancestry with elephants. But rhinoceroses are actually
related to horses and tapirs, in the Mammalian Order for odd-toed
ungulates, Perissodactyla. Like the other perissodactyls, rhinos
have mesaxonic feet, which means the center toe bears much of the
weight. Rhinos have three toes, which are large and splayed out to
support their bulky body. Also like horses, rhinos are hindgut
fermenters, bearing the ability to eat less nutritious vegetation
than ruminants because digestion is faster. All species of rhino are
herbivorous, either grazing on grasses or browsing on shrubbery.
Rhinos are primarily solitary, found together only to breed, with
calf, or at a shared resource. Males are territorial, defending
their territory aggressively. The two African rhino species joust
with their horns, while the Asian rhino species battle with their
lower inscisors, and in the case of the Sumatran rhino - its lower
canines. Females travel throughout different territories, using
resources as needed.
Rhinoceros eyesight is very poor. A motionless person at 100ft (30m)
is undetectable to a rhino. However, what rhinos lack in sight is
accounted for in audition and olfaction. A rhino's hearing is
extremely sensitive, capable of noticing the slightest of sounds.
But a rhino's cardinal sense is smell. The volume of olfactory
passages in the snout exceeds that of the brain!
Unfortunately, not even the keenest sense of smell can save the
rhino from human hunters. Poached for its magnificent horn, all
species of rhino are in danger of extinction. Rhino populations are
now increasing due to protection from national park systems and
captive breeding programs in zoos throughout the world.