Currently, there are five species of rhinoceros in the world, which are the black rhino, the white rhino, the Indian rhino, the Sumatran rhino and the Javan rhino. No matter the species, all rhinoceroses have poor eyesight, and tend to rely heavily on their senses of smell and hearing for survival and communication.
Rhinoceroses use a wide variety of vocalizations in order to communicate, including squeaks, moos, snorts, growls and trumpets. Sumatran rhinoceroses are known to string together a series of sounds to create an ongoing "song." One of these sounds is similar to the song of a humpback whale. The first sounds a baby rhinoceros makes are high-pitched squeaks and mewling squeals.
Using Breath to Communicate
Rhinoceroses often make use of a complex system of breathing to signal to one another. When a mother rhinoceros becomes separated from her calf, for instance, she calls to the infant with breathing pants. The way rhinos use breath to communicate is similar to Morse code. The speeds of the breathing vary and, depending on the speed and pattern, may indicate anything from anxiety to reassurance.
Some rhinoceros sounds are infrasonic—below the range of human hearing. Researcher Elizabeth von Muggenthaler discovered this in 1990, when she inadvertently picked up an infrasonic sound made by a rhino while trying to record that of an elephant. Some of these infrasonic sounds are quite resonant and powerful. The whistle-blow of the Sumatran rhinoceros, for instance, has a strong infrasonic content. The sound, which is a whistle followed immediately by a burst of air, is capable of causing 7-inch iron bars to resonate, and may carry up to 12 miles in a rhino's natural habitat.
Rhinos rely heavily on olfactory communication through scent marking in order to identify one another and to indicate their presence at feeding stations and watering holes. Dung piles, called middens, are often used as a message board for rhinos. A rhino will sniff the midden and shuffle through it, then defecate on it. Bull rhinos will kick the contents of the midden to get the scent on their feet before moving on. Bull rhinos also spray on trees or bushes as a way to communicate their presence, often spraying a single bush or tree as many as four times.
Rhinos sometimes make use of their ears, nostrils and posture to communicate. They may indicate curiosity with erect ears or an erect tail, or show anger by flattening their ears and flaring their nostrils. Bull rhinos will bash their heads into bushes to show aggression during mating. Body language is the least important way in which rhinos communicate, because of their poor eyesight.