Black Rhino, Diceros bicornis 2003; minor update 2012

Fact Summary Taxonomy and Nomenclature Distribution and Habitat Physical Characteristics Behavior and Ecology Diet and Feeding Reproduction and Development Diseases and Pathology Managed Care Population and Conservation Status Web Resources Bibliography

Describer (Date): Linnaeus 1758 (Diceros bicornis)
                               
Kingdom: Animalia
    Phylum: Chordata
        Class: Mammalia
             Order: Perissodactyla
                Suborder: Ceratomorpha (rhinos and tapirs)
                    Family: Rhinocerotidae
                           Genus: Ceratotherium (white rhinos)
                           Genus: Dicerorhinus (Sumatran rhinos)
                           Genus: Rhinoceros (Javan and Indian rhinos)
                           Genus: Diceros
                                 Species: Diceros bicornis (black rhino)
                                        Subspecies/Ecotypes: D. b. longipes (western black rhino)
                                                                           D. b. michaeli (eastern black rhino)
                                                                          D. b. bicornis (southwestern black rhino)
                                                                          D. b. minor  (south central black rhino)

• Subspecies
  • Some disagreement still exists regarding subspecies or "ecotypes" (see du Toit, 1987, and Rookmaaker, 1995).
  • To simplify communication, the African Rhino Workshop in Cincinnati (1986) proposed four groupings, knowing that they were not necessarily subspecifically different. However many researchers refer to these as subspecies (Rookmaaker, 1998).
  • Amato et al. (1993) did not find significant genetic differences between the groups.
  • Source for subspecific nomenclature above: IUCN African Rhino Specialist Group (see Emslie and Brooks, 1999).

• Probably called Black Rhinoceros to differentiate it from the White Rhinoceros. It is likely that "white" is a misunderstanding of the Afrikaans word "weit" (wide, as in "wide-lipped"). Skin coloration between the two species is the same.
• Other common names for black rhino: browse rhino, prehensile-lipped, hook-lipped, rhinoceros noir (Fr.), Spitzmaulnashorn (Gr.), Faru (Swah.).

• Closest living relative: tapirs
• Evolutionary history :
  • Perissodactyls (odd-toed hoofed mammals) first appear in the fossil record around around 58 million years ago (upper Paleocene)
  • Over the last 50 million years, rhinocerotids became extremely diverse ecologically, and various species were distributed throughout the globe.
  • Earliest known rhino-and horse-like ancestor: Hyrachyus (Superfamily: Rhinocerotidae), is found in Wyoming, Europe, Canadian Arctic, and possibly Asia; middle Eocene; the size of a large dog, with hooves, herbivorous teeth, but hornless.(Prothero et al. 1986)
  • Indian rhinoceroses first appeared around 26 million years ago (late Oligocene) (Steiner & Ryder 2011)
  • Summatran rhinoceroses had evolved by 25 million years ago (late Oligocene) (Steiner & Ryder 2011)
  • The black and white rhinoceroses of Africa didn't evolve until around 17 million years ago (early Miocene) (Steiner & Ryder 2011)
  • By around 7 million years ago (Miocene) black and white rhinos became distinct genetically (Brown & Houlden 2000)
  • Once widespread in North America, died out there about 4 million years ago.
  • Extinct Woolly Rhino (hairy, with flattened saber-like horn) lived in Eurasia during the ice age and became extinct around 12,000 years ago (Late Pleistocene) (Kuzmin 2009); some specimens have been found frozen in permafrost and preserved in peat bogs.
• Oldest modern rhino lineage: Indian rhinos with their single horns (Steiner & Ryder 2011)

• Previously distributed widely in sub-Saharan Africa; everywhere except extremely mesic and xeric areas.
• Presently occurs only in small isolated pockets in sub-Saharan Africa
• D. b. longipes (western): Historical- savannahs of central western Africa.  Present- Cameroon
• D. b. michaeli (eastern): Historical- S Sudan, Ethiopia, and Somalia, through Kenya to N central Tanzania. Present- Mostly Kenya; small numbers in Rwanda and Tanzania, and a game reserve in South Africa (well outside its range).
• D. b. bicornis (southwestern): Historical- Namibia, S Angola, W Botswana, and SW South Africa. Present- Most in deserts and arid savannahs of Namibia; reintroduced populations in South Africa and other parts of Namibia; possibly a few in Angola.
• D. b. minor (south central): Historical- W, S Tanzania through Zambia, Zimbabwe and Mozambique to N and E South Africa. Present- Mostly in South Africa (stronghold) and Zimbabwe; fewer in Swaziland, S Tanzania, and Mozambique.

Historic and present distribution,  from Intl Rhino Foundation	Distribution of subspecies, from (Emslie & Brooks, 1999)

• Savannahs with a high diversity of woody shrubs and herbaceous plants.
• Not found in closed canopy forests or open grasslands

• Very thick, gray skin with deep folds; heavy, stocky body; short neck, large head; almost hairless; Three hooved toes, central toe is largest and takes most of the weight; small tail with tuft of hair at the tip.
• Large, robust cheek teeth; no canines or incisors
• Skin color often obscured by dirt due to wallowing in mud or dust.
• Horns:
  • Two horns on the rostrum, one in front of the other.
  • Made of keratin (like true horns)
  • No bony core; not attached to skull; not shed
  • Ever-growing
• Species level differences:
• Black: Two horns, skin hairless, no incisors, low-crowned molars, upper lip triangular-shaped and prehensile.
• White: Two horns, skin hairless, no incisors, high crowned molars, upper lip square shaped and not prehensile, large hump behind head, largest species.
• Indian: One horn, skin hairless, tusk-like lower incisors, high crowned molars, prehensile upper lip, skin forms heavy folds like armor plating, posterior of neck plate continuous, large bumps on skin of shoulder, upper arms and upper legs.
• Javan: One horn which is only horny knob in female, skin hairless, tusk-like lower incisors, low-crowned molars, prehensile upper lip, skin forms heavy folds like armor plating, posterior of neck plate separated, skin with mosaic-like pattern rather than large bumps.
• Sumatran: Two horns which are very small in the female, skin hairy, lower incisors present but not tusk-like, prehensile upper lip, skin fold forming only a few divisions, no folds near nose. Smallest species.
• Subspecific differences: D. b. michaeli has longer, thinner, more curved horn, and is more aggressive. D. b. bicornis is larger, has a straighter horn, and is adapted to a more arid habitat.

• It can be difficult to tell males from females
• Older females have more of a sway-back, presumably due to carrying heavy calves during various pregnancies.

• Male with backward facing genitalia (as in hippo)
• Males w/o scrotum (testes abdominal)
• Female with two teats
• Poor eyesight
• Good sense of smell and hearing

• Active both day and night
• Field observations in Kenya show the following general daily activity pattern:
  • Most inactive between 10:00 AM and 3:00 PM, the hottest part of the day.
  • Most feeding occurs in the hours before and after this inactive period.
  • Most watering activity (traveling to and drinking water) was observed between 3:00 and sundown.
  • Specific activity patterns (involving time, location, and activity) vary among individuals, and among consecutive days for a single individual.
• Wallowing
  • Rest in the shade and wallow in shallow mud pools during the heat of the day. In Tanzania, 90% of wallowing occurred between 4:00 and 6:00 PM (Goddard, 1967).
  • Sometimes rests and sleeps in shallow water.
  • Will wallow in dust if mud is not available.
  • Wallowing helps reduce the animal's body temperature (mud and water), and protects against ectoparasites (dust).
• Most of the time rests/sleeps laying down, but sometimes while standing.

• Do not form organized social groups, but individuals often congregate in small groups for short periods.
• Females with young tend not to socialize with other adults, and may form the only stable associations.
• Adult males socialize the least, but do occasionally tolerate the presence of others.
• Merz (1991) observed individual treatment by a dominant male towards each of five females during mating, suggesting a more complex social interaction than was previously thought.

• Little information exists in the literature regarding social dominance.

• Level of territoriality (defending a specific patch of ground) is unclear. Territorial behavior has been described as (1) territorial, (2) territorial, but shared trails that may bisect one or more territories, (3) not territorial.
• Territorial size of radio-tracked black rhino in Natal: males 3.9 to 4.7  km²; females 5.8 to 7.7 km².
• Merz (1991) describes preferred day time resting spots or "houses" that are frequently revisited .
• Some are shared by several individuals, some are used only by one or two.
• Tend to be on high ground
• Individuals tend to lie facing downwind; often align themselves with the shadow of a large horizontal branch (if present) for better camouflage.
• Home range (undefended area where an animal ranges in search of food)
  • Size varies (seasonally, and between different habitat types) and depends on resource availability.
  • In habitats with an abundance of food and water, home ranges tend to be smaller, and rhino density tends to be higher.
  • Home ranges of individuals often overlap, and neighbors tend to tolerate each other without aggression.
• Home range size: 2.6 to 44 km² in Ngorongoro, and 43 to 133 km² in the Serengeti.