Historically, there were more than 200 species of rhinoceros. In the 21st century, only five species remain. Three species of rhino live in Asia, two in Africa. These massive animals compensate for poor eyesight with highly developed senses of hearing and smell. The rhino’s sense of smell is its most powerful -- his olfactory center is larger than all other parts of his brain combined.
Rhinos rely primarily on their sense of smell to communicate with other rhinos, using feces and urine to mark their territories. A rhinoceros will kick his feces with his feet, spreading his scent wherever he walks. Scent marking is important because rhinos are solitary creatures with poor eyesight, and they use it to find other rhinos and locate feeding grounds and watering holes. A mother rhino uses her sense of smell to keep track of her offspring, and the young rhino in turn uses his sense of smell to find his mother.
A rhino’s sense of smell is of utmost importance during mating. Female rhinos spray urine and scrape their feces more often when they are in season, signaling to male rhinos that they're sexually receptive. A male rhinoceros who is following a particular female may cover her urine spray with his own, or scatter the dung she has scraped. This sends a message to other males that she has a pursuer, and also makes it more difficult for them to attempt to follow her.
Due to their size and strength, adult rhinos have no true natural predators. Lions and hyenas prey on young rhinos, and lions may attack an adult, particularly if it's sick or injured. The rhino’s sense of smell alerts it to predators or other potential threats. Rhinos are dangerous because, if a rhino smells a potential threat, he may charge blindly toward the source without further investigation. Because of poaching, rhinos in the wild have learned to fear humans as predators and will aggressively charge any person who fails to approach from downwind.
Despite laws and treaties protecting the rhinoceros, they remain vulnerable to poachers. People carve rhino horns into dagger handles or pound them into a powder used in Asian traditional medicine as treatment for everything from headaches and fevers to more serious ailments such as typhoid. Because rhinos had no significant predators prior to humans, they never learned avoidance techniques. The rhino’s sense of smell aids the animal in escaping poachers, but most have learned only to approach the animal from downwind.
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