Black Rhinoceros
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[Photo] A Black Rhinoceros. Info: By John and Karen Hollingsworth in Tanzania / US Fish and Wildlife Service. Source: USFWS (file)
The Black Rhinoceros, Diceros bicornis also colloquially Black Rhino is a mammal in the order Perissodactyla, native to the eastern and central areas of Africa including Kenya, Tanzania, Cameroon, South Africa, Namibia and Zimbabwe. Although the Rhino is referred to as a "Black" creature, it is actually more of a grey-white colour in appearance.
The name of the species was chosen to distinguish it from the White Rhinoceros (Ceratotherium simum). This is very misleading, as those two species are not really distinguishable by colour. The word "White" in name "White Rhinoceros" deriving from the Afrikaans word for "wide" rather than the colour white.
The World Conservation Union (IUCN) announced on 7 July 2006 that the West African Black Rhinoceros subspecies (Diceros bicornis longipes) has been tentatively declared as extinct.[1]
Anatomy
An adult Black Rhinoceros stands 143 ??? 160 cm (56-63 inches) high at the shoulder and is 2.86-3.05 m (9.3-10 feet) in length. An adult weighs from 800 to 1400 kg (1,760 to 3,080 lb), exceptionally to 1820 kg (4,000 lb), with the females being smaller than the males. Two horns on the skull are made of keratin with the larger front horn typically 50 cm long, exceptionally up to 140 cm. always, a third smaller horn may develop. These horns are used for defense, intimidation and digging up roots and break branchs during feeding. Skin color depends more on local soil conditions and their wallowing behavior than anything else, so many black rhinos are typically not truly black in color.
The Black Rhinoceros is much smaller than the White Rhinoceros, and has a pointed, prehensile upper lip, which they use to grasp leaves and twigs when feeding. White Rhinoceros have square lips used for grazing grass. The Black Rhinoceros can also be recognized from the White Rhinoceros by its smaller skull and ears and its more pronounced forehead. Black Rhinoceros also do not have a distinguishing shoulder hump like the White Rhinoceros.
Their thick layered skin protects the rhino from thorns and sharp grasses. Although their skin harbours many external parasites, which are eaten by oxpeckers and egrets that live with the rhino.They have terrible eyesight relying more on hearing and smell. It has large ears that rotate much like satelite dishes to detect any sound and a large nose that has an excellent sense of smell to detect predators.
Behavior and Ecology
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. Its been known to eat up to 220 different species of plant. It can live up to 5 days without water during drought. Black Rhinos lives in primarily in grasslands, savannahs and tropical bushland habitat.
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 evening.
Solitary animals with the exception of coming together to mate, mothers and calfs, and sometimes congregate in small groups for short periods of time. Males are not as sociable as females although 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 has plenty of food and water available and vice versa if resources is not readily available. In the Serengeti home ranges range 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. Due to their very poor eyesight if they sense danger they will charge just in case. They have even been observed to charge tree trunks and termite mounds. Although they are not very aggressive towards others of the same species. Usually only bluffing towards each other. Males will fight sometimes by pushing head to head or horn jousting. They usually avoid other males when possible. Females are not aggressive towards each other.
Black Rhinos follow the same trails as elephants used to get from foraging areas to water holes. They also use smaller trails when they are browsing. Very fast and can get up to speeds of 35 miles per hour running on their toes.
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 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 either just smell to see who is in the area and add their own marking. Less commonly they will rub their head or horn 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 it is angry. Sneeze like calls are used as an alarm to danger. Short snorts with pricked ears and wrinkled nostrils is a startle reaction to a newcomer. A high-pitched wonk has been described for when they are fearful. Even worse is a high-pitched scream observed when they are terrified. "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. Also breathing long and slow, or short and quick 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 or visual signs is the least important of Black Rhino communications. A bull will sometimes display an aggressive ritual towards a potential rival. They will smell, spray repeatedly, scrape, trample, and bash with its head all to a bush. It may also snort in attack posture. When their tail is up, it may indicate one of several things. They might be simply curious, as an alarm, or if a female is ready to mate. Ears straight up may say it's curious as well. Ears flat, however, shows it is angry.
Reproduction
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 drier environments.
Spraying can identify a female that is receptive. Another common behavior of locating a mate is a called "Making Flehman". Its when the males lip curl, nose wrinkle, and head lift to better smell female pheromones. When in season the females will scrape more vigorously at dung piles. Males following females that are in season will follow her and 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.
There is courtship behaviors before mating which includes snorting and sparring with the horns. Another courtship behavior called bluff and bluster where the rhino will snort and swing its head side to side aggressively and then run away. It will repeatedly do this behavior. 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. They are polygamous and mate with more than one rhino.
The gestation period is 15 ??? 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 years old for females, from 7 years for males, and the life expectancy in natural conditions (without poaching pressure) is from 35 ??? 50 years.
Population
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 number severely reduced from an estimated 70,000[3] in the late 1960s to only 10,000 to 15,000 in 1981. In the early 1990s the number dipped below 2500, and in 1995 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.[4] 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 savannahs of western Africa but had dropped to just 10, concluded the subspecies to be extinct. [5] 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 only 50 a century ago.[6]
Subspecies
There are four subspecies of the black rhinoceros:
- 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) which 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, Somalia down through Kenya into north-central Tanzania. Today, its range is limited primarily to Tanzania.
- West African (Diceros bicornis longipes) is the rarest and most endangered subspecies. Historically, it once occurred across most of the west African savanna. Until recently, only a few individuals survived in northern Cameroon, but on July 8, 2006 the World Conservation Union declared the subspecies to be tentatively extinct.
http://en.wikipedia.org/wiki/Black_Rhinoceros
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