Kingdom: Animalia Phylum: Chordata Class: Mammalia Order:
Perissodactyla Suborder: Ceratomorpha (rhinos and tapirs) Family: Rhinocerotidae 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) Taxonomy
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).
Common Names
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.).
Phylogeny
Closest living relative: Tapirs
Evolutionary history: Over the last 50 million years,
rhinocerotids were extremely diverse ecologically, and distributed
throughout the globe. Once widespread in North America, they died out
there about 4 million years ago.
Earliest known ancestor: Hyrachus, from Wyoming, Europe,
Canadian Arctic, and possibly Asia; middle Eocene; the size of a large
dog, with hooves, herbivorous teeth (cross crests), but hornless.
Most primitive living rhino: Sumatran rhino, Dicerorhinus
sumatrensis: fossil ancestors found in Europe, Asia, and
Africa; split off from other rhinos 15-20 million years ago; relative
of the extinct Woolly Rhino, (hairy, with flattened saber-like horn)
which lived in Eurasia during the ice age; specimens have been found
frozen and preserved in peat bogs.
Fossil vs. DNA evidence: very different timelines (as much
300%) for the speciation of modern rhino genera. The times given above
are based on fossil evidence.
Distribution of subspecies,
from (Emslie & Brooks, 1999)
Distribution
Previously widespread in sub-Saharan Africa; everywhere except
extremely wet or dry 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.
Habitat
Savannahs with a high diversity of woody shrubs and herbaceous plants.
Not found in closed canopy forests or open grasslands
Body Weight: 1,000 - 1,800 kg (2200 - 3970 lbs) Body Length (head/body): 2.9 - 3.75 m (114-148 in.) Tail Length: 60 - 70 cm (24 - 28 in.) Shoulder Height: 1.4 - 1.8 m (55 - 71 in.)
General
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 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. Other
subspecific differences difficult to detect.
Sexual Dimorphism
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.
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.
Social Groups
General
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.
Hierarchy
Little information in literature regarding social dominance.
Territorial Behavior
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 is often higher.
Home ranges of individuals may overlap, and neighbors
generally tolerate each other without aggression.
Home range size: 2.6 to 44 km2
in Ngorongoro, and 43 to 133 km2
in the Serengeti.
Aggression
Overall, little aggression is shown towards one another, but encounters
of "bluff and bluster" are not
uncommon.
Aggressive encounters
Male to male: Fight occasionally (horn-jousting,
head-pushing) or exhibit a threat reaction. Males have also been
observed feeding and traveling together. However, most of the
time they avoid each other.
Female to Female: Do not generally act aggressively toward
one another. Aggressive encounters are short and often involve
facing one another and pushing head to head.
Male and Female: Usually occurs prior to mating.
"Bluff and bluster" displays may last for hours.
Ears flat, sometimes with wrinkled nose and grimace: anger
Eyes not very expressive
"Bluff and bluster": Upon meeting
another individual, one rhino snorts and swings head side-to-side in a
threatening manner, but will gallop away (swinging back around, often
repeating this behavior) if the other rhino lunges forward.
"Complex bull ceremony" described by Schenkel &
Schenkel-Hulliger (1969); occurs when male is alone, or when female
nearby; not always in this order or including all elements; probably
"symbolized aggression" toward a potential rival.
Sniffing a bush
Snorting in attack posture
Bashing bush with rostrum and horn; forceful, side to side
movement of head
Trampling bush and scraping with hind feet
Urinating in bursts over plant
Vocalization
Merz (1991) observed several types of vocalizations in black rhinos:
Lion-like growl and elephant-like trumpet
(heard during a fight).
Long snort (anger)
Short snort, like a sneeze (alarm)
Short snort with pricked ears and wrinkled nostrils
(startle reaction to newcomer)
"High-pitched wonk" (fear)
High-pitched scream (terror)
"Mmwonk", a deep, resonant sound
(contentment)
Squeak, done with different tones and intonations can
mean "I'm lost", "Where are you?",
"I'm over here", and other emotions that are not
yet understood.
Breathing (long and slow, or short and quick) can be
used to communicate greetings, anxiety, and reassurance.
"Puffing snort" is a common greeting when males and
females encounter one another (Goddard, 1967).
In contrast, vocal communication in white rhinos seems much less
common.
Olfaction/Scent
Marking
Sent marking is a very important method of communication in rhinos
because of their poor eyesight and more solitary nature.
Urine spraying
Males and females mark bushes or dung piles with a backwards,
horizontal spray of urine.
Both can shoot up to 3 to 4 meters.
Females do this most often when they are in season,
spraying in short bursts.
A male may come and spray over a female's scent marking.
Spraying also occurs along feeding or watering tracks.
Different than regular urination, and is used in
communication.
Dung Piles:
Often defecate in the same place repeatedly (="lavatories")
along feeding tracks, near water sources, and scattered randomly
throughout the home range.
"Calling cards": When approaching the dung pile
of another individual, a rhino may just sniff, or add to the pile
(defecate and scrape). Smelling the dung piles may be a way for
rhinos to identify each other.
Scent trails: dragging the hind feet after defecation
enables a rhino to leave a scent trail as it walks through its
home range, assisting with orientation. Other individuals may
follow the scent trail.
Two individuals traveling together often defecate in the
same spot (one after the other) or at the same time. This happens
with a mother and her young, as well as with two adults.
Female receptivity: females tend to scrape more vigorously
when sexually receptive.
Courtship: Sometimes a male follows a receptive female and
scrapes her dung vigorously (flinging it far away) every time she
defecates. This makes it more difficult for other males to follow
her scent.
Head rubbing: against trunk or stump may be method of scent
marking; horn rubbing less common.
Making Flehman: mostly done by male when sniffing rear end or
urine mark of receptive female. Flehmen is a German word describing
characteristic behavior- lip curl, nose wrinkle, and head lift. It is
thought to aid in bringing scent to the Jacobson's organ (also called
vomeronasal organ), located far back in the palate, which detects
trace quantities of chemicals in the air (i.e., pheromones).
Locomotion
In Kenya, rhinos and elephants follow wide trails (several km long),
with little vegetation, that go between water and feeding areas. A
smaller network of trails, usually not used by elephants, is shared
with other wildlife, and used for during foraging (Schenkel &
Schenkel-Hulliger, 1969).
Sedentary; tend not to disperse very rapidly.
Interspecies Interaction
Rhinos have learned to fear humans. Exhibit defense behaviors if
the scent of humans is detected.
Due to poor eyesight, they have learned to react to the alarm
reaction of other ungulates. If they detect a possible threat, but are
not able to see it from a distance, they often charge it just in case.
They have been observed charging tree trunks and termite mounds.
Symbiotic relationships with other species:
Cattle Egret- eats the insects stirred up by rhino as it walks;
often sits on its back, but rarely picks off ectoparasites.
Fork-tailed drongo- sits on branches near rhino, swoops in and out
(much like flycatchers) eating insects that are attracted to it.
Does not follow rhino outside its home range.
Red-billed Oxpecker- climbs on rhino (even into ears and nostrils)
and plucks off insects. Will follow rhino for long distances.
Also serves as alarm when danger approaches (very high pitched
alarm call).
Elephants: although they share many of the same food plants,
rhinos and elephants usually do not interact with each other.
Exception- when food and water resources are scarce. Elephants can be
beneficial by digging wallows and pulling down branches with leaves
(elephants tend to eat larger branches, rather than the smaller
twigs). But they can be detrimental by disturbing the habitat
(destruction of trees and bushes).
DIET & FEEDING
(Kingdon, 1997)(Merz, 1991)
Diet
Browsers: eat leaves, twigs, and branches. Merz (1991)
reported that long grass may constitute up to 30%-40% of the
diet, but grass consumption is usually very low.
Up to 220 plant species recorded (99 woody, 102 herbs, and
25 grasses).
Diet (quantity and species of plants) changes in relation
to seasons and rainfall (and therefore, availability).
Dung is often inspected to detect diet. Difference between
rhino and elephant dung: rhinos scrape
dung pile with back feet, flinging it away, leaving two parallel
grooves; contains small, short twigs. Elephant dung left in
undisturbed piles; contains longer, twisted pieces of woody fiber.
Feeding Behavior
Prehensile lip of black rhino enables it to specialize on
different diet than white rhino (short grass and herbaceous
plants, but no leaves/twigs from trees or bushes).
Horns used to dig up roots and break branches for better
access to food.
As with horses and zebras, digest food by bacterial
fermentation in hind gut .
Water
Can go up to 5 days without drinking if food contains sufficient
moisture. If only dry forage is available, they will be found
within a day's travel to water.
Handle drought conditions well compared to many other animal
species in the area. Not susceptible to poisonous tannins in
plants that often increase during a drought.
Cocking the tail- Females, when sexually aroused; tail
lifts and is cocked at an angle
Making flehman- Mostly males; seen in many other
ungulate groups; see Olfaction/Scent
Marking
Dung scraping- Females; scrape dung pile more
energetically (more often, with more force) than usual.
When a female is in estrus, a male may follow her for
a long distance, trying to become accepted as a mating
partner. May follow calmly, approach with stiff, dragging
legs, or exhibit "Bluff and bluster"
display. Occasionally, male and female face each other
nudging heads and jousting with horns, neither of which is
done with great force.
Polygamous: both males and females mate with more than one
individual.
Males do not defend harems of females, as seen in some
ungulates. However, males have been observed to defend a receptive
female by charging a potential competitor.
Reproduction
Breeds year round; no discreet breeding season.
Estrus lasts three days and occurs every 25-30 days.
Copulation lasts for half an hour or more.
Partnering can last from one mating session, to days, weeks, or
sometimes months.
Can be difficult to tell when a female is in season. See
Courtship above for clues.
Also difficult to tell when a female is pregnant until a few
days before she gives birth.
First parturition: 3.5 to 5.7 years old; varies group to group
and depends on density and resource availability.
Interbirth Interval: 2.5 to 4 years
Gestation:15-17 months in the wild; 15-18 months in
captivity
Life Stages
Birth
Litter size: 1
Birth weight: 27 - 45 kg
Infant (< 1 year old)
Starts nibbling on solid food (grass; small, non-woody plants) in 7 to
10 days.
Immature
Independent of mother at 2.5 to 3 years old. When
new calf is born, mother rejects the older calf.
May find a non-related adult to join after being rejected.
Adult
Reports of sexual maturity vary widely
Females: 3.5 to 4 years (Schenkel & Schenkel-Hulliger, 1969)
or maturity at 7 years and may conceive as young as 3.8 years
(Estes, 1991).
Males: 6 years, fully grown at 8 to 10 years (Schenkel &
Schenkel-Hulliger, 1969) or maturity reached at 10 years (Estes,
1991).
Longevity (Rookmaaker, 1998)
Fairly high mortality in zoos; approximately 60% have died within 10
years of being placed in captivity.
Record longevity (as of 1994) for captive is 44 years old.
Approximately 40 years in the wild.
Mortality
Drought: Survive better than many species, but still vulnerable
to its affects. New mothers and their calves are the most vulnerable
due to reduction in availability of nutritious food. Pregnant females
often abort their fetuses. Malnutrition kills an animal directly
or makes it more vulnerable to parasites and disease.
Poachers: Because black rhinos tend to revisit the same resting
spots during the day, they are more vulnerable to poachers. See Threats to Survival for more on poaching.
Predators: Humans are the main predators of rhinos. Lion and
hyena attacks on rhinos are rare, and usually only occurs with sick or
young animals.
DISEASES AND PATHOLOGY
(Schenkel & Schenkel-Hulliger, 1969)
Ectoparasites
Ticks- several species; mostly in folds of skin,
genital and anal regions, eyes, and ears
Biting flies- several species; large numbers
congregate on the hide; suck blood mostly from saddle
region; seem to be discouraged by soil layer on skin from
mud wallows.
Endoparasites
Microfilaria (small nematode worm) have been found in
ulcerating wounds; Stephanofilaria dinniki
Intestinal helminths, in both small and large
intestines; Anoplocephala sp. and Kiluluma sp.
Fly larvae, found in lining of the stomach; large size
and quantity; Gyrostigma sp.
Roundworm; found in the conjunctiva (membrane of the
eye); Thelaziid
Third century BC: first written records of rhinoceros being
exhibited, by the Romans. Sporadic exhibitions continued through the
3rd century AD.
First through 14th century AD: often given as gifts in
China.
6th (N. Africa) and 16th-17th centuries (Near East): sporadic
records of captivity.
1868: First black rhino in captivity in a European zoo.
1941: First born in captivity, Chicago Brookfield Zoo.
1952: San Diego Zoo obtains its first rhino (black).
1976: First black rhino born at the Wild Animal Park.
1992: First black rhino born at San Diego Zoo
Present:
San Diego Zoo: south central black rhinos (Diceros
bicornis minor) Wild Animal Park: northern white rhinos (Ceratotherium
simum cottoni), southern white rhinos (Ceratotherium simum
simum), eastern black rhinos (Diceros bicornis michaeli),
and Indian rhinos (Rhinoceros unicornis).
POPULATION AND CONSERVATION STATUS
(Ashley et al., 1990)(Emslie, 2002)(Emslie & Brooks, 1999)
(Leader-Williams, 1992)(Schenkel & Schenkel-Hulliger, 1969)
Population Status
Wild/game reserve populations
By Year
1800's: hundreds of thousands; fairly
continuous throughout much of sub-Saharan Africa
Most rhinos now live in protected, managed game reserves.
It is imperative to understand the seasonal shift in diet when setting
up protective reserves. Many rhinos have been poached after wandering
off a reserve looking for food during a drought.
The threat of poaching is still so prevalent, that some
conservationists condone the practice of dehorning managed
populations, thus eliminating the temptation to poachers.
Management through sustainable use is controversial (ecotourism, trophy
hunting, horn harvesting, and trade in rhino products).
Threats to survival
Unmanaged populations tend to be small and isolated, and
therefore, more vulnerable to disease, inbreeding, and local
extinction.
Vulnerability to poachers
Poor eyesight; poachers can sneak up more easily as
long as they are down wind.
Prior to human encroachment, rhinos did not suffer from
predation pressure and therefore, did not evolve behavior or
sensory capability to avoid predators. In Recent times they
have learned some avoidance tactics. See Interspecies Interactions.
Sedentary nature, and regular activity patterns (for
example, revisiting resting and watering spots), make it
easier for poachers to find them.
Reasons for poaching
Horns
Medicinal uses (most common): to help fevers, headaches,
toxins, typhoid, jaundice, rashes, vomiting or
excreting blood, to keep evil away, etc.
Carved cups and dagger handles
Aphrodisiac: contrary to popular thought, rarely used
this way; mostly by the Gujaratis in India.
Asian ("fire") horns thought by some to be
more potent than African ("water") horns
resulting in more hunting pressure for Asian species.
Blood (medicinal)
Skin (medicinal)
Poaching market, major consumers
All rhino products: mostly China and Taiwan, but also Burma,
Thailand, and Nepal.
Horns, medicinal uses: Japan and Korea
Horns, dagger handles: Yemen (carved dagger handle is status
symbol)
Also a strong market in countries with immigrants from these
places (e.g., the Chinese living in the US)
Problems enforcing conservation laws
Civil war and political instability
Poverty due to exponential population growth, hyperinflation,
and corruption
Well armed poaching gangs
Competition for land (leading to habitat destruction) by
increasing populace.
Other comments on poaching
It is likely that any improvement in health is due to the
placebo effect (because of strong traditional beliefs),
rather than to any real curative properties. Few scientific
studies have been done, and have conflicting results (see
Leader-Williams, 1992).
Earliest evidence of horn use for medical reasons: 2600 BC,
China.
It is still legal to sell rhino products in many countries,
and in others, enforcement is often lax.
