Diceros bicornis
black rhinoceros

Historically, Diceros bicornis has been distributed throughout Africa, south of the Sahara, with the exception of the Congo Basin. The current range of black rhinoceroses is bounded by Cameroon, Kenya, and South Africa but their distribution within those limits is fragmented. (Brooks, 2002; Grzimek, 2005; World Wildlife Fund, 2004)

Black rhinoceroses live in various habitats that range from deserts to grasslands, both tropical and subtropical. They are also present in African forests, especially in areas where grasslands and forests phase into one another. Black rhinos generally stay within 25 kilometers of water. (Grzimek, 2005; Massicot, 2006; World Wildlife Fund, 2004)

Although the color of black rhinoceroses can vary from yellow-brown to dark-brown, the general color is grey. Specific skin color depends on the soil conditions within the habitat of each individual. The skin is naked or hairless, with the exception of short, fringe-like hair on the short and rounded ears. On average, black rhinos have a shoulder height between 1.4 and 1.8 m, a head and body length between 3 and 3.75 m, and a weight between 800 and 1400 kg. Tail length is generally around 0.7 m. Although similar in size, males are normally a little larger than females. (Grzimek, 2005; Lang, 1983; World Wildlife Fund, 2004)

Black rhinos have two horns, one posterior and one anterior, which are made from keratin instead of bone. The anterior horn is normally longer, measuring 42 to 128 cm, while the posterior horn is 20 to 50 cm. In some cases, black rhinos have a third, posterior horn, which is small. Females tend to have longer and thinner horns than males. (Brooks, 2002; Grzimek, 2005; Massicot, 2006; World Wildlife Fund, 2004)

The trait that distinguishes black rhinos from white rhinos is the pointed, prehensile upper lip found in black rhinos, as opposed to the square lips found in white rhinos. This lip is used to pick up food such as twigs. Additionally, black rhinos have smaller heads, shorter ears, and shorter horns than white rhinos. (Brooks, 2002; Lang, 1983; World Wildlife Fund, 2004)

Adult black rhinos are typically solitary creatures. However, during mating, black rhino adults come together. Black rhinos are polygynous. Male rhinos begin a courtship by following females, including their dependent offspring, for approximately one or two weeks before mating actually begins; even while sleeping, the male and female remain in contact with one another. Males exhibit certain behavioral characteristics before mating: they walk in a stiff-legged manner and brush their horns along the ground in front of the female. Before copulation begins, many attempts by the male to mount the female are made; if the female is not yet ready, she will make a series of attacks or charges at the male. When insertion is actually achieved, copulation lasts between 20 and 40 minutes. If the mating is unsuccessful, females return to a state of heat within 35 days of the previous copulation. (Garnier, et al., 2001; Garnier, et al., 2002; Grzimek, 2005; Hillman-Smith and Groves, 1994; Massicot, 2006)

Breeding occurs throughout the year but peak breeding season varies by location. Gestation lasts approximately 15 months. Females give birth to one offspring at a time, which usually weighs between 20 and 25 kg. Weaning of offspring typically occurs after 18 months, but offspring remain dependent for up to 4 years. Females achieve sexual maturity at age 5 to 7 years; males reach maturity between 7 and 8 years. (Brooks, 2002; Dollinger and Geser, 2008; Garnier, et al., 2002; Grzimek, 2005)

For the first week after birth the offspring is hidden by the mother. After that, the mother and calf use specific vocalizations to find one another: the mother pants and the calf squeals. Black rhino mothers are very protective of their calves, which is why calves walk behind their mothers. This differs from white rhino females, who have their young walk in front of them. Calves are able to browse on their own after one month and able to drink water after 4 to 5 months. Black rhino offspring aren’t weaned until 18 months; after that, the calf remains dependent on its mother for up to 4 years. The basic social unit for females is typically a female and her young offspring, until the offspring is forced into independence by a sibling. (Garnier, et al., 2001; Grzimek, 2005; Massicot, 2006)

Typical lifespan in the wild is between 30 and 35 years, with little expectation of exceeding 35 years. In captivity, black rhinos can live over 45 years, with the record being 49 years. Factors that limit lifespan in the wild include poaching for horns and habitat fragmentation. (Brooks, 2002; Grzimek, 2005; Massicot, 2006)

Typically, black rhinos are relatively solitary. Males remain solitary until it is time to mate; females reside with their young offspring in a solitary family unit. There are exceptions, as females without young sometimes associate with other females. The largest black rhino group that has been observed so far has been made up of 13 rhinos, but this was a temporary association. (Hillman-Smith and Groves, 1994)

Black rhinos have a sedentary lifestyle and remain in one general area. They are less active during the middle of the day, using mornings and evenings to eat, drink, and move around. When they are startled, they tend to run away from the source. While fleeing, rhinos issue a series of snorts and curl their tails until they calm down. Once the initial scare has passed, the rhino’s curiosity kicks in, and it will examine the source with inquisitive charges. Even though there is severe danger associated with black rhino charges, the charge normally does not end with serious consequences. (Hillman-Smith and Groves, 1994; Massicot, 2006)

In order to remain cool during especially hot times of the day or season, black rhinos roll in mud to get it all over their bodies. They also make trips to local salt licks to get needed nutrients necessary for survival. (Grzimek, 2005)

Adult black rhinos defecate on dung piles as a means of communication, as it reveals to other rhinos how recently an individual was in a certain location. Males also use their feces to mark territories; they kicking their feces to get fecal material on their feet, then move around their home range. They also urinate to mark their home range. When two females meet, they demonstrate little aggression, merely approaching each other and possibly nudging each other with their horns, and then retreating. However, when two males or a male and a female meet, more aggression is exhibited. Upon meeting, a male and female interact in the way described the above. When two males meet, however, violence can very easily ensue. Many times, the less dominant of the two retreats. If not, the males charge at one another, horn first and groaning loudly. The anterior horn provides the rhinos with a very effective weapon during the interaction. (Hillman-Smith and Groves, 1994; Massicot, 2006; Hillman-Smith and Groves, 1994; Massicot, 2006)

There is large variation in home range size of black rhinos. Depending on region and habitat, home range can range from 2.6 km^2 to 133 km^2. Habitats with better conditions generally result in smaller home ranges, while poorer conditions result in larger home ranges, presumably because rhinos have to travel further to acquire food and water. Black rhinos are not excessively territorial within their home ranges, but dominant males are more likely to express territorial behavior against other dominant males than females and males lower down in the hierarchical system. (Hillman-Smith and Groves, 1994)

Although black rhinos use vision, acoustic, and smell senses, their sense of smell is what they rely on most. They have poor vision, with the ability to see only 25 to 30 m away. Their sense of hearing is good, but not up to the level of their sense of smell. Black rhinos use the pheromones and scents from their feces and urine to mark territories. Additionally, they engage in calls to one another that can take the form of the pant-squeal interaction seen in mothers and their infants to loud roars that signify aggression. When a subordinate male enters the territory of a more dominant male, the combination of calls and territorial scents causes the subordinate male to retreat. (Hillman-Smith and Groves, 1994; Massicot, 2006)

Black rhinos are browsers that feed on items such as twigs, woody shrubs, small trees, legumes, and grass. Black rhinos show a preference for Acacia species, as well as plants in the family Euphorbiaceae. They eat an average of 23.6 kg during the course of each day. Black rhinos use their characteristic prehensile upper lip to grab plants and guide them into their mouths, where their cheek teeth can do the rest of the work. In addition, black rhinos use their horns to gain access to higher branches by breaking or knocking down plants. Scraping bark off of trees is also part of the repertoire of black rhino feeding. (Grzimek, 2005; Hillman-Smith and Groves, 1994; Massicot, 2006)

Humans, Homo sapiens, are the most important predator of black rhinos; however, both lions (Panthera leo) and spotted hyaenas (Crocuta crocuta) sometimes prey on young rhinos. Lions also sometimes attack adults. Black rhinos use their size and strength as a defense mechanism by charging at their predators both to threaten predators and actively defend themselves and their offspring. (Berger, 1994; Hillman-Smith and Groves, 1994)

Black rhinos and oxpeckers (Buphagus species) are involved in a mutualistic relationship where the oxpeckers eat parasites taken from the rhino’s skin. Additionally, oxpeckers are able to warn rhinos of approaching predators because their vision is much better than the rhino’s vision. Black rhinos are significant herbivores and influence plant communities. (Hillman-Smith and Groves, 1994; Massicot, 2006)

Black rhinos have the potential to help create awareness for conservation efforts. Additionally,they provide educational value both through biology and through art. Black rhino horns are also very valuable for their use in various products, such as traditional Chinese medicine and traditional Yemen dagger handles. The popularity of their horns is a major reason why the species as a whole is in trouble. (Brooks, 2002; Dollinger and Geser, 2008)

Although many charges by black rhinos towards humans and their vehicles turn into innocent advances, some may cause injury or death to humans, or damage to vehicles that results in monetary loss. (Grzimek, 2005)

Black rhinos have been on Appendix I of CITES since 1977. Additionally, black rhinos have been listed since 1980 under the United States Endangered Species Act. Black rhinos are listed as critically endangered by the IUCN Red List. Currently, there are four subspecies of black rhinos: D. bicornis bicornis, D. bicornis longipes, D. bicornis minor, and D. bicornis michaeli. The first subspecies is listed as vulnerable on the IUCN 2008 Red List, and the latter three are all listed as critically endangered. Conservation efforts to preserve black rhinos include establishing a ban against the horn trade, creating fenced sanctuaries for black rhinos to better protect them from poachers, and dehorning black rhinos to decrease incentive for poaching. With these efforts, the total population of 2,400 black rhinos towards the end of the twentieth century increased to 3,100 black rhinos by 2001. (Brooks, 2002; Convention on International Trade in Endangered Species of Wild Fauna and Flora, 2009; IUCN Species Survival Commission, 2008; U.S. Fish and Wildlife Service, 2009; World Wildlife Fund, 2004)