Black Rhinoceros

Black Rhinoceros or Hook-lipped Rhinoceros[1]
Conservation status
Critically Endangered (IUCN 3.1)[2]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Perissodactyla
Family:	Rhinocerotidae
Genus:	Diceros
Species:	D. bicornis
Binomial name
Diceros bicornis (Linnaeus, 1758)
Subspecies
Diceros bicornis michaeli Diceros bicornis longipes † Diceros bicornis minor Diceros bicornis bicornis
Black Rhinoceros range

The Black Rhinoceros or Hook-lipped Rhinoceros (Diceros bicornis), is a species of rhinoceros, native to the eastern and central areas of Africa including Kenya, Tanzania, Cameroon, South Africa, Namibia, Zimbabwe, and Angola. Although the Rhino is referred to as black, it is actually more of a grey/brown/white color in appearance.

The name of the species was chosen to distinguish it from the White Rhinoceros (Ceratotherium simum). This is misleading, as those two species are not really distinguishable by color. The word white in the name "White Rhinoceros" is a mistranslation of the Dutch word wijd for wide, referring to its square upper lip, as opposed to the pointed or hooked lip of the Black Rhinoceros. They are now often referred to as the Square-lipped (for White) or Hook-lipped (for Black) Rhinoceros.

The World Conservation Union (IUCN) announced on 7 July 2006 that one of the four subspecies, the West African Black Rhinoceros (Diceros bicornis longipes), has been tentatively declared as extinct.^[3]

Taxonomy and naming

There are four subspecies of the black rhinoceros:^[4]

• South-central (Diceros bicornis minor) which are the most numerous, and once ranged from central Tanzania south through Zambia, Zimbabwe, and Mozambique to northern and eastern South Africa.
• South-western (Diceros bicornis bicornis) are better adapted to the arid and semi-arid savannas of Namibia, southern Angola, western Botswana, and western South Africa.
• East African (Diceros bicornis michaeli) which had a historic distribution from south Sudan, Ethiopia, down through Kenya into north-central Tanzania. Today, its range is limited primarily to Tanzania.
• West African (Diceros bicornis longipes) is an extinct subspecies. Historically, it once occurred across most of the north-western Cameroon, but on July 8, 2006 the World Conservation Union declared the subspecies to be tentatively extinct.^[3] There are no known Western Black Rhinos in captivity.

Description

Black rhino in Ngorongoro crater, Tanzania

An adult Black Rhinoceros stands 140–170 cm (55–67 in) high at the shoulder and is 3.3–3.6 m (11–12 ft) in length.^[5] An adult weighs from 800 to 1,400 kg (1,800 to 3,100 lb). The females are smaller than the males. 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 horn measured nearly 1.5 m (4.9 ft) in length.^[6] Sometimes, a third smaller horn may develop. These horns are used for defense, intimidation, and digging up roots and breaking branches during feeding. Skin color depends more on local soil conditions and the rhinoceros' wallowing behavior than anything else, so many black rhinos are typically not truly black in color. The Black Rhino is much smaller than the White Rhino, and has a long, pointed, and prehensile upper lip, which it uses to grasp leaves and twigs when feeding.^[6] White Rhinoceros have square lips used for eating grass. The Black Rhinoceros can also be recognized from the White Rhinoceros by its smaller skull and ears.

Their thick layered skin protects the rhino from thorns and sharp grasses. Their skin harbors many external parasites, such as mites and ticks, which are eaten by oxpeckers and egrets that live with the rhino. Such behaviour was originally thought to be an example of mutualism, but recent evidence suggests that oxpeckers may be parasites instead^[7]. Black rhinos have relatively poor eyesight, relying more on hearing and smell. Their ears possess a relatively wide rotational range to detect sounds and an excellent sense of smell to readily alert them the presence of predators.

Distribution

Black rhinos in Ngorongoro crater, Tanzania

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 later half of the 20th century their numbers were severely reduced from an estimated 70,000^[8] 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, the total African population has since then slightly recovered to 3,610 by 2003.^[9] According to a July 2006 report by the World Conservation Union, a recent survey of the West African Black Rhino, which once ranged across the savanna of western Africa but had dropped to just 10, concluded the subspecies to be extinct.^[10] The northern white is soon to join the western black rhino on the extinction list as its last noted numbers were as few as 4. The only rhino that has recovered somewhat from the brink of extinction is the southern white whose numbers now are estimated around 14,500, up from fewer than 50 in the first decade of the 20th Century.^[11] The Black Rhinoceros has been pushed to the brink of extinction by illegal poaching for their horn and by loss of habitat. The horn is used in traditional Chinese medicine, and is said by herbalists to be able to revive comatose patients, cure fevers, and aid male sexual stamina and fertility.^[12] The purported effectiveness of the use of rhino horn in treating any illness has not been confirmed 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.^[12] It is used in the Middle East 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.

Behavior

Solitary animals with the exception of coming together to mate, mothers and calves will sometimes congregate in small groups for short periods of time. Males are not as sociable as females, although they will sometimes allow the presence of other rhinos. 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. In the Serengeti home ranges are around 43 to 133 km², while in the Ngorongoro it is between 2.6 to 44 km². 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.

The Black Rhino has a reputation for being extremely aggressive. They attack out of fear, confusion, and panic. They will charge if they sense a threat, which occurs frequently due to their very poor eyesight. 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.^[13] Adult Black Rhinos have no natural predators^[14], outside of an unverified incident of a huge Nile crocodile taking one down.^[15]

Black Rhinoceros follow the same trails as 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 56 kilometres per hour (35 mph) running on their toes.

Diet

Black rhino grazing, Sydney Zoo

The Black Rhinoceros is a herbivorous browser that eats leafy plants, branches, shoots, thorny wood bushes, and fruit. Their diet helps to reduce the amount of woody plants which results in more grasses growing for the benefit of other animals. It has been known to eat up to 220 different species of plant. It can live up to 5 days without water during drought. Black Rhinos live in primarily grasslands, savannas, and tropical bushland habitats.

They browse for food in the morning and evening. In the hottest part of the day they are most inactive spent resting, sleeping, and wallowing in the mud. Wallowing is an essential part of all rhino species lives. It helps cool down their body temperature during the day and protects against parasites. If mud is not available they will resort to wallowing in dust. Drinking water is most commonly done towards the afternoon. When Black Rhinos browse they use their lips to strip the branches of their leaves.

Communication

Many forms of communication are exhibited by these animals. Due to their bad eyesight and solitary nature, scent marking is often used to identify other Black Rhinos. Urine spraying occurs on trees and bushes, around water holes and feeding areas. Females urine spray more often when receptive for breeding. Defecation occurs in the same spot used by many different rhinos found around feeding stations, watering tracks, and other areas. These are very important for identifying each other. Coming upon these spots, rhinos will smell to see who is in the area and add their own marking. Less commonly they will rub their heads or horns against tree trunks to scent mark.

Different types of complex vocalizations have also been observed. Growls and trumpets may be used during a fight. A long snort indicates anger, while sneeze-like calls are used as an alarm to danger. Short snorts with pricked ears and wrinkled nostrils are a startled reaction to a newcomer. A high-pitched wonk has been described for when they are fearful. Even worse is a high-pitched scream observed in times of terror. "Mmwonk", a deep, resonant sound is a sign of 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 speeds can be used to communicate greetings, anxiety, and reassurance. A puffing snort is a common greeting when males and females encounter one another.

Body language is the least important of Black Rhinoceros communications. A bull will sometimes display an aggressive ritual towards a potential rival. They will smell, spray repeatedly, scrape, trample, and bash with their heads in bushes. They may also snort in an attack posture. When their tail is up, it may indicate one of several things: curiosity, alarm, or sexual receptivity. Erect ears also indicate curiosity, though flat ears express anger.

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 females will scrape their vaginas more vigorously with dung piles. Males following females that are in season will follow her; when she defecates he will scrape and spread the dung, making it more difficult for any other adult males 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 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 an hour.

The gestation period is 15 to 16 months. The single calf weighs about 35–50 kg 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 5–7 years old for females, and 7–8 years for males. The life expectancy in natural conditions (without poaching pressure) is from 35–50 years.^[5]

Footnotes

References

• Emslie, R. and Brooks, M. (1999). African Rhino. Status Survey and Conservation Action Plan. IUCN/SSC African Rhino Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK. ISBN 2831705029 
• Rookmaaker, L. C. (2005). "Review of the European perception of the African rhinoceros". Journal of Zoology 265 (4): 365–376. doi:10.1017/S0952836905006436 

External links

• Black Rhino Info & Black Rhino Pictures on the Rhino Resource Center website.
• The International Rhino Foundation dedicated to the conservation of rhinos http://www.rhinos-irf.org/
• "Black Rhinos Fact Sheet; developed for the San Diego Zoological Society Intranet". http://spot.colorado.edu/~humphrey/fact%20sheets/rhino_black/black_rhino.htm. Retrieved 2007-10-09. 
• "Black Rhinoceros" (PDF). Zoological Parks Board of New South Wales. http://www.zoo.nsw.gov.au//imagedata/Rhi.pdf. Retrieved 2007-10-09. 
• www.savetherhino.org
• WildLifeNow Website for the Tony Fitzjohn/George Adamson African Wildlife Preservation Trust, supporting the Mkomazi Game Reserve and Mkomazi Rhino Sanctuary in Tanzania
• U.S. Fish & Wildlife Service Species Profile