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Lifespan, longevity, and ageing

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Maximum longevity: 49 years (captivity) Observations: One wild born specimen was about 49 years old when it died in captivity (Richard Weigl 2005).
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Benefits

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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.

Negative Impacts: injures humans

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Kurnit, J. 2009. "Diceros bicornis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Diceros_bicornis.html
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Jennifer Kurnit, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Associations

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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.

Known Predators:

  • lions (Panthera leo)
  • spotted hyaenas (Crocuta crocuta)
  • humans (Homo sapiens)
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Kurnit, J. 2009. "Diceros bicornis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Diceros_bicornis.html
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Jennifer Kurnit, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Morphology

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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.

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.

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.

Range mass: 800 to 1400 kg.

Range length: 3.0 to 3.75 m.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: sexes alike; male larger; sexes shaped differently; ornamentation

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Kurnit, J. 2009. "Diceros bicornis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Diceros_bicornis.html
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Jennifer Kurnit, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Life Expectancy

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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.

Average lifespan
Status: wild:
35 years.

Average lifespan
Status: captivity:
49 years.

Typical lifespan
Status: wild:
30 to 35 years.

Typical lifespan
Status: captivity:
30 to 45 years.

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Kurnit, J. 2009. "Diceros bicornis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Diceros_bicornis.html
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Jennifer Kurnit, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Habitat

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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.

Habitat Regions: temperate ; tropical ; terrestrial

Terrestrial Biomes: desert or dune ; savanna or grassland ; scrub forest

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Kurnit, J. 2009. "Diceros bicornis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Diceros_bicornis.html
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Jennifer Kurnit, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Distribution

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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.

Biogeographic Regions: ethiopian (Native )

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Kurnit, J. 2009. "Diceros bicornis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Diceros_bicornis.html
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Jennifer Kurnit, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Trophic Strategy

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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.

Plant Foods: leaves; wood, bark, or stems; seeds, grains, and nuts

Primary Diet: herbivore (Folivore , Lignivore)

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Kurnit, J. 2009. "Diceros bicornis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Diceros_bicornis.html
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Jennifer Kurnit, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Associations

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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.

Ecosystem Impact: disperses seeds

Mutualist Species:

  • oxpecker (Buphagus africanus)
  • oxpecker (Buphagus erythrorhynchus)

Commensal/Parasitic Species:

  • Rhinoussa brucei
  • Gyrostigma
  • Ixodidae
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Kurnit, J. 2009. "Diceros bicornis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Diceros_bicornis.html
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Jennifer Kurnit, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Benefits

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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.

Positive Impacts: body parts are source of valuable material; source of medicine or drug ; research and education

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Kurnit, J. 2009. "Diceros bicornis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Diceros_bicornis.html
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Jennifer Kurnit, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Conservation Status

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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.

US Federal List: endangered

CITES: appendix i

State of Michigan List: no special status

IUCN Red List of Threatened Species: critically endangered

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Kurnit, J. 2009. "Diceros bicornis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Diceros_bicornis.html
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Jennifer Kurnit, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Behavior

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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.

Communication Channels: visual ; tactile ; acoustic ; chemical

Other Communication Modes: pheromones ; scent marks

Perception Channels: visual ; tactile ; acoustic ; chemical

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Kurnit, J. 2009. "Diceros bicornis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Diceros_bicornis.html
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Jennifer Kurnit, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Reproduction

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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.

Mating System: polygynous

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.

Breeding interval: Black rhinos breed every 2 to 2.5 years under the most favorable conditions, but interbreeding periods can last up to 4 years.

Breeding season: Black rhinos mate throughout the year, with peak breeding seasons depending on the location of the population.

Average number of offspring: 1.

Average gestation period: 15 months.

Average weaning age: 18 months.

Range time to independence: 2 to 4 years.

Range age at sexual or reproductive maturity (female): 5 to 7 years.

Range age at sexual or reproductive maturity (male): 7 to 8 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous

Average birth mass: 36500 g.

Average gestation period: 474 days.

Average number of offspring: 1.

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.

Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Protecting: Female)

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Kurnit, J. 2009. "Diceros bicornis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Diceros_bicornis.html
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Jennifer Kurnit, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Tanya Dewey, Animal Diversity Web
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Biology

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Black rhinoceros are mainly solitary creatures, occupying overlapping home ranges (5). In this long-lived species females reach sexual maturity at around five to seven years old and give birth to a single calf every two to four years (6). Births can occur throughout the year and each calf tends to remain with its mother until the birth of her next offspring. Rhinoceros have poor eyesight but a keen sense of smell and hearing (5). They are inquisitive and often aggressive towards humans and other animals (4). Using their prehensile lip, black rhinoceros feed on the leaves and twigs of a variety of woody plants and herbs (4). Foraging often occurs in the cool of dawn and dusk; they spend much of the rest of the day resting in the shade or wallowing in shallow water holes, coating their skin in mud to protect it from the harsh sun and to deter biting flies (2).
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Conservation

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The population crash in the latter half of the 20th Century saw rhinoceros numbers plummet to a low of about 2,400 individuals (4). A variety of conservation approaches have been adopted, which have resulted in the stabilisation and partial recovery of populations in a number of countries. The most successful have involved the rigorous protection of rhinoceros in fenced sanctuaries, often in partnerships between the State and private sectors, or in intensely protected unfenced zones within larger areas (4). Dehorning has also been used in some countries to reduce the incentives to poach (4). In 1997, Yemen became a signatory of the Convention on International Trade in Endangered Species (CITES), thus greatly reducing the demand for rhinoceros horn in the Middle East (7). By 2001, the continental black rhinoceros population had increased to 3,100, with populations in six of the eight range states increasing (4). Most individuals are conserved in heavily protected areas. The African Rhino Specialist Group of the World Conservation Union (IUCN) provides advice on the conservation of African rhinoceros, and has developed a detailed Action Plan, which provides extensive information and strategic direction for their conservation (4).
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Description

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The black rhinoceros is the most well known of the five living rhinoceros species, with its aggressive reputation and highly publicised international conservation drive. Black rhinoceros are in fact grey in colour and are distinguished from the other African species (which is also grey) the white rhinoceros (Ceratotherium simum), by its pointed, prehensile upper lip; white rhinoceros have square lips (2). Both African rhinoceros species possess two horns, made from clumped fibres rather than bone, and the taller front horn may be 60 centimetres or longer (4).
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Habitat

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Inhabits a variety of habitats, ranging from the deserts of Namibia through wooded grasslands to broadleaved woodlands and acacia savannahs (4).
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Range

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Once found throughout much of sub-Saharan Africa with the exception of the Congo Basin and other equatorial forest areas of West Africa (4). The recent decimation of the species has restricted the range to fragmented populations, predominately existing in reserves in Kenya, Tanzania, Namibia, Zimbabwe, South Africa, Cameroon, Malawi and Swaziland (4). Four subspecies are recognised in different areas of the species range: the southwestern (Diceros bicornis bicornis), western (D. b. longipes), eastern (D. b. michaeli) and south-central black rhinoceros (D. b. minor) respectively (1).
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Status

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Classified as Critically Endangered (CR) on the IUCN Red List 2007 (1) and listed on Appendix I of CITES (3). Subspecies: southwestern black rhinoceros (D. b. bicornis) classified as Vulnerable (VU); western black rhinoceros (D. b. longipes), eastern black rhinoceros (D. b. michaeli) and south-central black rhinoceros (D. b. minor) are all classified as Critically Endangered (CR) on the IUCN Red List 2007 (1).
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Threats

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Black rhinoceros have been poached to the brink of extinction due to the demand for their horn, both for use in Chinese traditional medicine and for traditional dagger handles in Yemen, the demand for which exploded in the 1970s due to the increased income of oil-rich Gulf States (7). It is estimated that between 1970 and 1992, around 96 percent of the black rhinoceros population was lost (8).
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Black rhinoceros

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The black rhinoceros, black rhino or hook-lipped rhinoceros (Diceros bicornis) is a species of rhinoceros, native to eastern and southern Africa including Angola, Botswana, Kenya, Malawi, Mozambique, Namibia, South Africa, Eswatini, Tanzania, Zambia, and Zimbabwe. Although the species is referred to as black, its colours vary from brown to grey. It is the only extant species of the genus Diceros.

The other African rhinoceros is the white rhinoceros (Ceratotherium simum). The word "white" in the name "white rhinoceros" is often said to be a misinterpretation of the Afrikaans word wyd (Dutch wijd) meaning wide, referring to its square upper lip, as opposed to the pointed or hooked lip of the black rhinoceros. These species are now sometimes referred to as the square-lipped (for white) or hook-lipped (for black) rhinoceros.[6]

The species overall is classified as critically endangered (even though the south-western black rhinoceros is classified as near threatened) and is threatened by multiple factors including poaching and habitat reduction. Three subspecies have been declared extinct, including the western black rhinoceros, which was declared extinct by the International Union for Conservation of Nature (IUCN) in 2011.[7][8] The IUCN estimates that there are 3,142 mature individuals remaining in the wild.[2]

Taxonomy

The species was first named Rhinoceros bicornis by Carl Linnaeus in the 10th edition of his Systema naturae in 1758. The name means "double-horned rhinoceros". There is some confusion about what exactly Linnaeus conceived under this name as this species was probably based upon the skull of a single-horned Indian rhinoceros (Rhinoceros unicornis), with a second horn artificially added by the collector. Such a skull is known to have existed and Linnaeus even mentioned India as origin of this species. However he also referred to reports from early travellers about a double-horned rhino in Africa and when it emerged that there is only one, single-horned species of rhino in India, Rhinoceros bicornis was used to refer to the African rhinos (the white rhino only became recognised in 1812).[9] In 1911 this was formally fixed and the Cape of Good Hope officially declared the type locality of the species.[10]

Subspecies

The intraspecific variation in the black rhinoceros has been discussed by various authors and is not finally settled.[11] The most accepted scheme considers seven or eight subspecies,[4][12][13] of which three became extinct in historical times and one is on the brink of extinction:

The most widely adopted alternative scheme only recognizes five subspecies or "eco-types": D. b. bicornis, D. b. brucii, D. b. longipes, D. b. michaeli, and D. b. minor.[17] This concept is also used by the IUCN, listing three surviving subspecies and recognizing D. b. brucii and D. b. longipes as extinct. The most important difference to the above scheme is the inclusion of the extant southwestern subspecies from Namibia in D. b. bicornis instead of in its own subspecies, whereupon the nominal subspecies is considered extant.[2]

Evolution

The rhinoceros originated in the Eocene about fifty million years ago alongside other members of Perissodactyla.[18] Ancestors of the black and the white rhinoceros were present in Africa by the end of the Late Miocene about ten million years ago.[18] The two species evolved from the common ancestral species Ceratotherium neumayri during this time. The clade comprising the genus Diceros is characterised by an increased adaptation to browsing. Between four and five million years ago, the black rhinoceros diverged from the white rhinoceros.[18] After this split, the direct ancestor of Diceros bicornis, Diceros praecox was present in the Pliocene of East Africa (Ethiopia, Kenya, Tanzania). D. bicornis evolved from this species during the Late PlioceneEarly Pleistocene,[19] with the oldest definitive record at the Pliocene–Pleistocene boundary c. 2.5 million years ago at Koobi Fora, Kenya.[20]

Description

An adult black rhinoceros stands 140–180 cm (55–71 in) high at the shoulder and is 3–3.75 m (9.8–12.3 ft) in length.[21][22] An adult typically weighs from 800 to 1,400 kg (1,760 to 3,090 lb), however unusually large male specimens have been reported at up to 2,896 kg (6,385 lb).[4][21] The cows are smaller than the bulls. Two horns on the skull are made of keratin with the larger front horn typically 50 cm (20 in) long, exceptionally up to 140 cm (55 in).

The longest known black rhinoceros horn measured nearly 1.5 m (4.9 ft) in length.[23] Sometimes a third, smaller horn may develop.[24] These horns are used for defense, intimidation, and digging up roots and breaking branches during feeding. The black rhino is smaller than the white rhino and close in size to the Javan rhino of Indonesia. It has a pointed and prehensile upper lip, which it uses to grasp leaves and twigs when feeding,[23] whereas the white rhinoceros has square lips used for eating grass. The black rhinoceros can also be distinguished from the white rhinoceros by its size, smaller skull, and ears; and by the position of the head, which is held higher than the white rhinoceros, since the black rhinoceros is a browser and not a grazer.

A black rhinoceros skull with restored horn

Their thick-layered skin helps to protect black rhinos from thorns and sharp grasses. Their skin harbors external parasites, such as mites and ticks, which may be eaten by oxpeckers and egrets.[25] Such behaviour was originally thought to be an example of mutualism, but recent evidence suggests that oxpeckers may be parasites instead, feeding on rhino blood.[26] It is commonly assumed that black rhinos have poor eyesight, relying more on hearing and smell. However, studies have shown that their eyesight is comparatively good, at about the level of a rabbit.[27] Their ears have a relatively wide rotational range to detect sounds. An excellent sense of smell alerts rhinos to the presence of predators.

Distribution

Prehistorical range

As with many other components of the African large mammal fauna, black rhinos probably had a wider range in the northern part of the continent in prehistoric times than today. However this seems to have not been as extensive as that of the white rhino. Unquestionable fossil remains have not yet been found in this area and the abundant petroglyphs found across the Sahara desert are often too schematic to unambiguously decide whether they depict black or white rhinos. Petroglyphs from the Eastern Desert of southeastern Egypt relatively convincingly show the occurrence of black rhinos in these areas in prehistoric times.[28]

Historical and extant range

The natural range of the black rhino included most of southern and eastern Africa, but it did not occur in the Congo Basin, the tropical rainforest areas along the Bight of Benin, the Ethiopian Highlands, and the Horn of Africa.[4] Its former native occurrence in the extremely dry parts of the Kalahari desert of southwestern Botswana and northwestern South Africa is uncertain.[29] In western Africa it was abundant in an area stretching east to west from Eritrea and Sudan through South Sudan to southeastern Niger, and especially around Lake Chad. Its occurrence further to the west is questionable, though often purported to in literature.[5] Today it is totally restricted to protected nature reserves and has vanished from many countries in which it once thrived, especially in the west and north of its former range. The remaining populations are highly scattered. Some specimens have been relocated from their habitat to better protected locations, sometimes across national frontiers.[2] The black rhino has been successfully reintroduced to Malawi since 1993, where it became extinct in 1990.[30] Similarly it was reintroduced to Zambia (North Luangwa National Park) in 2008, where it had become extinct in 1998,[31] and to Botswana (extinct in 1992, reintroduced in 2003).[32]

In May 2017, 18 eastern black rhinos were translocated from South Africa to the Akagera National Park in Rwanda. The park had around 50 rhinos in the 1970s but the numbers dwindled to zero by 2007. In September 2017, the birth of a calf raised the population to 19. The park has dedicated rhino monitoring teams to protect the animals from poaching.[33][34]

In October 2017, The governments of Chad and South Africa reached an agreement to transfer six black rhinos from South Africa to Zakouma National Park in Chad. Once established, this will be the northernmost population of the species. The species was wiped out from Chad in the 1970s and is under severe pressure from poaching in South Africa. The agreement calls for South African experts to assess the habitat, local management capabilities, security and the infrastructure before the transfer can take place.[35]

Behavior

A cow with calf
Black rhino at Moringa waterhole, Etosha National Park

Black rhinos are generally thought to be solitary, with the only strong bond between a mother and her calf. In addition, bulls and cows have a consort relationship during mating, also subadults and young adults frequently form loose associations with older individuals of either sex.[36] They are not very territorial and often intersect other rhino territories. Home ranges vary depending on season and the availability of food and water. Generally they have smaller home ranges and larger density in habitats that have plenty of food and water available, and vice versa if resources are not readily available. Sex and age of an individual black rhino influence home range and size, with ranges of cows larger than those of bulls, especially when accompanied by a calf.[37] In the Serengeti home ranges are around 70 to 100 km2 (27 to 39 sq mi), while in the Ngorongoro it is between 2.6 to 58.0 km2 (1.0 to 22.4 sq mi).[36] Black rhinos have also been observed to have a certain area they tend to visit and rest frequently called "houses" which are usually on a high ground level. These "home" ranges can vary from 2.6 km2 to 133 km2 with smaller home ranges having more abundant resources than larger home ranges.[38]

Black rhinos in captivity and reservations sleep patterns have been recently studied to show that males sleep longer on average than females by nearly double the time. Other factors that play a role in their sleeping patterns is the location of where they decide to sleep. Although they do not sleep any longer in captivity, they do sleep at different times due to their location in captivity, or section of the park.[39]

Black rhinos have a reputation for being extremely aggressive, and charge readily at perceived threats. They have even been observed to charge tree trunks and termite mounds. Black rhinos will fight each other, and they have the highest rates of mortal combat recorded for any mammal: about 50% of males and 30% of females die from combat-related injuries.[40] Adult rhinos normally have no natural predators, thanks to their imposing size as well as their thick skin and deadly horns.[41] However, adult black rhinos have fallen prey to crocodiles in exceptional circumstances.[42] Calves and, very seldom, small sub-adults may be preyed upon by lions as well.[4]

Black rhinos follow the same trails that elephants use to get from foraging areas to water holes. They also use smaller trails when they are browsing. They are very fast and can get up to speeds of 55 kilometres per hour (34 mph) running on their toes.[43][44]

While it was assumed all rhinoceros are short-sighted, a study involving black rhinoceros retinas suggests they have better eyesight than previously assumed.[45]

Diet

Chewing on plants

Black rhinos are herbivorous browsers that eat leafy plants, twigs, branches, shoots, thorny wood bushes, small trees, legumes, fruit, and grass.[46][47] The optimum habitat seems to be one consisting of thick scrub and bushland, often with some woodland, which supports the highest densities. Their diet can reduce the number of woody plants, which may benefit grazers (who focus on leaves and stems of grass), but not competing browsers (who focus on leaves, stems of trees, shrubs or herbs). It has been known to eat up to 220 species of plants. They have a significantly restricted diet with a preference for a few key plant species and a tendency to select leafy species in the dry season.[48] The plant species they seem to be most attracted to when not in dry season are the woody plants. There are 18 species of woody plants known to the diet of the black rhinoceros, and 11 species that could possibly be a part of their diet too.[49] Black rhinos also have a tendency to choose food based on quality over quantity, where researchers find more populations in areas where the food has better quality.[50] Black rhinos show a preference for Acacia species, as well as plants in the family Euphorbiaceae.[51] In accordance with their feeding habit, adaptations of the chewing apparatus have been described for rhinos. The black rhinoceros has a two phased chewing activity with a cutting ectoloph and more grinding lophs on the lingual side. The black rhinoceros can also be considered a more challenging herbivore to feed in captivity compared to its grazing relatives.[52] They can live up to 5 days without water during drought. Black rhinos live in several habitats including bushlands, Riverine woodland, marshes, and their least favorable, grasslands. Habitat preferences are shown in two ways, the amount of sign found in the different habitats, and the habitat content of home ranges and core areas. Habitat types are also identified based on the composition of dominant plant types in each area. Different subspecies live in different habitats including Vachellia and Senegalia savanna, Euclea bushlands, Albany thickets, and even desert.[36] They browse for food in the morning and evening. They are selective browsers but, studies done in Kenya show that they do add the selection material with availability in order to satisfy their nutritional requirements.[53] In the hottest part of the day they are most inactive- resting, sleeping, and wallowing in mud. Wallowing helps cool down body temperature during the day and protects against parasites. When black rhinos browse they use their lips to strip the branches of their leaves. Competition with elephants is causing the black rhinoceros to shift its diet. The black rhinoceros alters its selectivity with the absence of the elephant.[54]

There is some variance in the exact chemical composition of rhinoceros horns. This variation is directly linked to diet and can be used as a means of rhino identification. Horn composition has helped scientists pinpoint the original location of individual rhinos, allowing for law enforcement to more accurately and more frequently identify and penalize poachers.[55]

Communication

Black rhinos use several forms of communication. Due to their solitary nature, scent marking is often used to identify themselves to other black rhinos. Urine spraying occurs on trees and bushes, around water holes and feeding areas. Cows urine spray more often when receptive for breeding. Defecation sometimes occurs in the same spot used by different black rhinos, such as around feeding stations and watering tracks. Coming upon these spots, rhinos will smell to see who is in the area and add their own marking. When presented with adult feces, bulls and cows respond differently than when they are presented with subadult feces. The urine and feces of one black rhinoceros helps other black rhinoceroses to determine its age, sex, and identity.[56] Less commonly they will rub their heads or horns against tree trunks to scent-mark.

The black rhino has powerful tube-shaped ears that can freely rotate in all directions. This highly developed sense of hearing allows black rhinos to detect sound over vast distances.[57]

Reproduction

Mother and calf in Lewa, central Kenya

The adults are solitary in nature, coming together only for mating. Mating does not have a seasonal pattern but births tend to be towards the end of the rainy season in more arid environments.

When in season the cows will mark dung piles. Bulls will follow cows when they are in season; when she defecates he will scrape and spread the dung, making it more difficult for rival adult bulls to pick up her scent trail.

Courtship behaviors before mating include snorting and sparring with the horns among males. Another courtship behavior is called bluff and bluster, where the black rhino will snort and swing its head from side to side aggressively before running away repeatedly. Breeding pairs stay together for 2–3 days and sometimes even weeks. They mate several times a day over this time and copulation lasts for a half-hour.

The gestation period for a black rhino is 15 months. The single calf weighs about 35–50 kilograms (80–110 lb) at birth, and can follow its mother around after just three days. Weaning occurs at around 2 years of age for the offspring. The mother and calf stay together for 2–3 years until the next calf is born; female calves may stay longer, forming small groups. The young are occasionally taken by hyenas and lions. Sexual maturity is reached from 5 to 7 years old for females, and 7 to 8 years for males. The life expectancy in natural conditions (without poaching pressure) is from 35 to 50 years.[58]

Conservation

Black rhino in the Maasai Mara

For most of the 20th century the continental black rhino was the most numerous of all rhino species. Around 1900 there were probably several hundred thousand[2] living in Africa. During the latter half of the 20th century their numbers were severely reduced from an estimated 70,000[59] in the late 1960s to only 10,000 to 15,000 in 1981. In the early 1990s the number dipped below 2,500, and in 2004 it was reported that only 2,410 black rhinos remained. According to the International Rhino Foundation—housed in Yulee, Florida at White Oak Conservation, which breeds black rhinos[60]—the total African population had recovered to 4,240 by 2008 (which suggests that the 2004 number was low).[61] By 2009 the population of 5,500 was either steady or slowly increasing.[62]

In 1992, nine black rhinos were brought from Chete National Park, Zimbabwe to Australia via Cocos Island. After the natural deaths of the males in the group, four males were brought in from United States and have since adapted well to captivity and new climate.[63] Calves and some subadults are preyed on by lions, but predation is rarely taken into account in managing the black rhinoceros. This is a major flaw because predation should be considered when attributing cause to the poor performance of the black rhinoceros population.[64] In 2002 only ten western black rhinos remained in Cameroon, and in 2006 intensive surveys across its putative range failed to locate any, leading to fears that this subspecies had become extinct.[16] In 2011 the IUCN declared the western black rhino extinct.[65] There was a conservation effort in which black rhinos were translocated, but their population did not improve, as they did not like to be in an unfamiliar habitat.

Under CITES Appendix I all international commercial trade of the black rhino horn is prohibited since 1977.[38] China though having joined CITES since 8 April 1981 is the largest importer of black rhino horns.[66] However, this is a trade in which not only do the actors benefit, but so do the nation states ignoring them as well. Nevertheless, people continue to remove the rhino from its natural environment and allow for a dependence on human beings to save them from endangerment.[67] Parks and reserves have been made for protecting the rhinos with armed guards keeping watch, but even still many poachers get through and harm the rhinos for their horns. Many have considered extracting rhino horns in order to deter poachers from slaughtering these animals or potentially bringing them to other breeding grounds such as the US and Australia.[67] This method of extracting the horn, known as dehorning, consists of tranquilizing the rhino then sawing the horn almost completely off to decrease initiative for poaching, although the effectiveness of this in reducing poaching is not known and rhino mothers are known to use their horns to fend off predators.[68]

The only rhino subspecies that has recovered somewhat from the brink of extinction is the southern white rhinoceros, whose numbers now are estimated around 14,500, up from fewer than 50 in the first decade of the 20th century.[69] But there seems to be hope for the black rhinoceros in recovering their gametes from dead rhinos in captivity. This shows promising results for producing black rhinoceros embryos, which can be used for testing sperm in vitro.[70]

A January 2014 auction for a permit to hunt a black rhinoceros in Namibia sold for $350,000 at a fundraiser hosted by the Dallas Safari Club. The auction drew considerable criticism as well as death threats directed towards members of the club and the man who purchased the permit.[71] This permit was issued for 1 of 18 black rhinoceros specifically identified by Namibia's Ministry of Environment and Tourism as being past breeding age and considered a threat to younger rhinos. The $350,000 that the hunter paid for the permit was used by the Namibian government to fund anti-poaching efforts in the country.[72]

In 2022 South Africa granted permits to hunt 10 black rhinos, stating that the population is growing.[73]

Threats

A black rhinoceros in the Savanna Bush diorama at the Milwaukee Public Museum

Today, there are various threats posed to black rhinos including habitat changes, illegal poaching, and competing species. Civil disturbances, such as war, have made mentionably negative effects on the black rhinoceros populations in since the 1960s in countries including, but not limited to, Chad, Cameroon, Rwanda, Mozambique, and Somalia.[2] In the Addo Elephant National Park in South Africa, the African bush elephant (Loxodonta africana) is posing slight concern involving the black rhinoceroses who also inhabit the area. Both animals are browsers; however, the elephant's diet consists of a wider variety of foraging capacity, while the black rhinoceros primarily sticks to dwarf shrubs. The black rhinoceros has been found to eat grass as well; however, the shortening of its range of available food could be potentially problematic.[74]

Black rhinos face problems associated with the minerals they ingest. They have become adjusted to ingesting less iron in the wild due to their evolutionary progression, which poses a problem when placed in captivity. These rhinoceroses can overload on iron, which leads to build up in the lungs, liver, spleen and small intestine.[75] Not only do these rhinoceros face threats being in the wild, but in captivity too. Black rhinoceros have become more susceptible to disease in captivity with high rates of mortality.[70]

Illegal poaching for the international rhino horn trade is the main and most detrimental threat.[2] The killing of these animals is not unique to modern-day society. The Chinese have maintained reliable documents of these happenings dating back to 1200 B.C.[76] The ancient Chinese often hunted rhino horn for the making of wine cups, as well as the rhino's skin to manufacture imperial crowns, belts and armor for soldiers.[76] A major market for rhino horn has historically been in the Middle East nations to make ornately carved handles for ceremonial daggers called jambiyas. Demand for these exploded in the 1970s, causing the black rhinoceros population to decline 96% between 1970 and 1992. The horn is also used in traditional Chinese medicine, and is said by herbalists to be able to revive comatose patients, facilitate exorcisms and various methods of detoxification, and cure fevers.[76] It is also hunted for the Chinese superstitious belief that the horns allow direct access to Heaven due to their unique location and hollow nature.[76] The purported effectiveness of the use of rhino horn in treating any illness has not been confirmed, or even suggested, by medical science. In June 2007, the first-ever documented case of the medicinal sale of black rhino horn in the United States (confirmed by genetic testing of the confiscated horn) occurred at a traditional Chinese medicine supply store in Portland, Oregon's Chinatown.[77]

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Black rhinoceros: Brief Summary

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The black rhinoceros, black rhino or hook-lipped rhinoceros (Diceros bicornis) is a species of rhinoceros, native to eastern and southern Africa including Angola, Botswana, Kenya, Malawi, Mozambique, Namibia, South Africa, Eswatini, Tanzania, Zambia, and Zimbabwe. Although the species is referred to as black, its colours vary from brown to grey. It is the only extant species of the genus Diceros.

The other African rhinoceros is the white rhinoceros (Ceratotherium simum). The word "white" in the name "white rhinoceros" is often said to be a misinterpretation of the Afrikaans word wyd (Dutch wijd) meaning wide, referring to its square upper lip, as opposed to the pointed or hooked lip of the black rhinoceros. These species are now sometimes referred to as the square-lipped (for white) or hook-lipped (for black) rhinoceros.

The species overall is classified as critically endangered (even though the south-western black rhinoceros is classified as near threatened) and is threatened by multiple factors including poaching and habitat reduction. Three subspecies have been declared extinct, including the western black rhinoceros, which was declared extinct by the International Union for Conservation of Nature (IUCN) in 2011. The IUCN estimates that there are 3,142 mature individuals remaining in the wild.

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