The best summary on this subject I have ever read actually, is the Status and Conservation part in the Family account in HMW II by Dr. Eric Dinerstein:
"The status and conservation of the rhinoceroses range from extraordinary hopeful to terribly pessimistic, depending on the species in question. Four features deserve closer inspection. First is the truly staggering contrast between the former dominance of rhinoceroses and their current rarity. Second is the extirpation of populations, reducing the free-ranging animals to a single location or fewer than five locations for several of the species. Third is the negative effect misguided captive breeding programs can have, as opposed to in-situ efforts buttressed by strict protection regimes and incentives to promote community participation in the conservation of endangered species. Fourth is that rhinos will remain what biologists term a "conservation-dependent" species; their survival and recovery depend on strict protection of all populations from poachers who seek their horns and from threats of conversion and degradation of their habitats by agricultural encroachment and infrastructure development.
Rhinoceroses were an abundant, widespread component of large mammal faunas on several continents for eons. The rapid decline of the extant species began at different stages for each of the five species. The Southern White Rhinoceros was abundant prior to the colonization of southern Africa, and dropped to its low point of less than 100 individuals in one game reserve in South Africa around 1900. It has made an astonishing recovery, from that nadir to today's global population, which, exceeding 17,000 animals, is often held up as the most remarkable example of wildlife recovery globally. Through intensive protection and translocation, Southern White Rhinos have been re-established from the founder population in the Hluhluwe-Umfolozi Game Reserve to other parks in southern Africa. That such a large, slow-breeding, long-lived mammal, under acute threat from poachers for its valuable horn, can show such a dramatic recovery buoys hope among conservationists not just for this population and the other rhinos, but for all endangered species.
The decline of the Northern White Rhino paints the opposite picture. In the decades before 1900, there may have been more Northern White Rhinos in Sudan, the Central African Republic, northern Uganda, and the DR Congo than Southern White Rhinos in South Africa. However, by the mid-1980s, civil wars and unrest led to widespread poaching in these countries and the Northern White Rhino population was decimated. The last stronghold became Garamba National Park in the DR Congo. A dedicated group of biologists and park rangers managed to grow this remnant population to at least 32 individuals before a further outbreak of poaching wiped out the rhinos by the mid-2000s. As of 2008, the World Conservation Union considered the remnant free-ranging population of Northern White Rhinos in Garamba National Park (DR Congo), to be extinct; however, there are as yet unsubstantiated rumors that a few animals may survive in a remote part of Sudan. The loss of this last population reinforces the strong link between civil unrest, war, and widespread availability of weapons in the countryside as the death sentence for endangered large mammals. Dedicated rangers can protect and recover endangered large mammals, but if the local populace is engaged in fighting, and if returned soldiers are allowed to keep their weapons upon cessation of armed conflict, extinction is the likely outcome. The demise of this population, considered a subspecies, became all the more tragic when in 2010 a scientific study provided morphological evidence and new genetic data elevating the Northern White Rhinoceros to full species status. This new designation, if it stands, would put the Northern White Rhino in the unenviable situation of going extinct before it was recognized in the scientific literature as a true species. The only hope of reviving this species is through a remnant population relocated from a Czech zoo to a private reserve in Kenya in the hope this will stimulate breeding. However, because these four animals are inter-related (founder genome equivalent of only 1·71), conservation biologists advise that the prognosis for the survival of “pure” Northern White Rhinos is not good and the best hope now is to try to conserve as much adaptive Northern White Rhino genes as possible for their eventual reintroduction into former range or in similar habitat nearby. This will probably require intercrossing of remaining Northern White Rhino with Southern White Rhino and there can be no guarantees this will succeed.
The Black Rhinoceros was once the most abundant of all five extant species across much of sub-Saharan Africa. Estimates of its numbers around 1900 range from 300,000 to 1,000,000. Black Rhinos experienced what biologists term a range collapse of epic proportions. Core populations were wiped out or greatly reduced in places like the Ngorongoro Conservation Area, Serengeti National Park, and Selous Game Reserve in Tanzania, across much of Zimbabwe, and in south-western Africa. The West African subspecies is likely extinct in the wild. Through intensive efforts by the African range states governments, with assistance from the African Elephant and Rhino Specialists Group of IUCN, NGOs, and foreign donors, the Black Rhino is staging a comeback. In some locales, small breeding populations were established in heavily protected game ranches. These populations recovered rapidly, but the limited spaces quickly reached carrying capacity. Translocations from these small ranches have helped to re-establish rhinos in more free-ranging situations. Perhaps the best success stories for this species both come from Namibia. Strict protection of Etosha National Park in north-central Namibia has allowed the population to grow to over 800 animals, and a massive translocation program has been instigated, supported by the Ministry of the Environment and the World Wildlife Fund. Even more promising is the presence of free-ranging Black Rhinos on communal conservancies in north-western Namibia. Here, local communities own the wildlife on their communal lands and protect it to generate revenues from ecotourism; they also protect game species on their lands for trophy hunting. This ecosystem service has sparked demand and competition from conservancies wanting to be able to show tourists free-ranging Black Rhinos without having to surround the tourists with armed guards as elsewhere in East Africa. The potential for this program bodes well for Black Rhino recovery efforts.
Some southern African countries experimented with a controversial technique to reduce the incentive to poach by dehorning free-ranging rhinos. This response was developed in desperation, poaching being rampant in the early 1990s, and resources inadequate to protect Black Rhinos in large remote reserves. One advantage of dehorning is that animals remain in their native habitats and established territories. Another advantage is that in remote areas, where frequent anti-poaching patrols are too costly, dehorning dissuades poachers from even searching for rhinos. Theoretically, only a portion of the population needs to be dehorned because, given the poachers' high failure rate, they would eventually give up hunting for rhinos with horns. The word would spread among poaching rings that the costs far outweighed the benefits of a successful poaching effort.
Namibia and Zimbabwe continued dehorning for several years, but eventually shut down these programs. The unit cost of dehorning proved too high—some estimates put the cost at US$ 1500 per individual. Compounding the high unit cost is that rhinoceros horn regenerates quickly. Poachers consider even a few centimeters—the first year's growth—valuable. In many areas, poachers appeared to have killed dehorned rhinos out of spite, or they shot first and looked later to find that the animal was hornless. Although sample sizes were small and the findings were disputed, some researchers suggested that dehorning Black Rhino cows exposed calves to high predation risks by hyenas and Lions. Dehorning, in hindsight, was a valiant but wasteful attempt to save a nucleus population until poaching could be brought under control. Even if initially successful, dehorning is only a stop-gap measure, impossible to maintain once a decimated population has recovered beyond a few dozen individuals.
The current estimate of the total free-ranging population of the three Asian species is less than 2700 individuals. Even more sobering is the statistic that only two populations of Asian rhinoceroses currently contain more than 100 individuals. The rapid decline of Asian rhinoceros populations is a direct result of relentless poaching pressure and loss of habitat.
Poaching has decimated populations among all three Asian species, but each shows a different trajectory and set of secondary threats. The status of the Greater One-horned Rhinoceros more closely resembles the Black Rhinoceros of Africa. Before agriculture spread to the Gangetic and Brahamputra River floodplains of south Asia in 1400 ad, the Greater One-horned Rhino may have numbered 475,000 or more. The presence of a deadly strain of malaria protected much of their habitat, making it unsuitable for humans until malaria was eradicated in the late 1950s. Only a few indigenous groups resistant to this strain lived near rhino habitat, and they did little poaching. Moreover, many of the current rhino sanctuaries were formerly royal hunting reserves and protected from intruders by the reigning monarchs. Two core populations remained in Royal Chitwan National Park in Nepal and Kaziranga National Park in Assam, India. However, populations declined to as low as 60–80 by the late 1950s and early 1960s in Nepal. Numbers dropped to less than 100 in Kaziranga around 1900. Many smaller reserves in Assam and West Bengal had numbers in the single digits or under 20 individuals in the 1970s.
Since 1986, the turnaround has been dramatic. Following the example of translocation programs designed to rebuild African rhino populations, the government of Nepal began an ambitious effort to translocate animals from Chitwan to other reserves. There are now five reserves in the western Terai zone of Nepal and India that contain rhinos from Chitwan. A similar ambitious translocation program is now underway in Assam with the goal of having a total population of 3000 distributed over seven reserves by 2020.
One major reason why rhinoceroses have persisted in Nepal and recovered from near-extinction, is that very few people have access to sophisticated firearms. Had Nepalese or Assamese villagers possessed the arsenals at the disposal of Somali poachers, the number of Greater One-horned Rhinoceroses would be much below its present level. Two dismal tests of this hypothesis may have already occurred in the Manas sanctuary of Assam, India, and in Bardia National Park, Nepal. An uprising by the Bodo people in Manas wiped out the existing population, estimated at about 80 Greater One-horned Rhinos, prior to the Bodos' temporary take-over of the sanctuary. In Bardia, 85 rhinos translocated to the Babai Valley in the 1980s and early 1990s were killed during a ten-year insurgency by Maoist rebels, which forced the Nepalese army from its guard posts and allowed local poachers access. (A smaller, translocated rhino population remains elsewhere in Bardia.) Even without widespread access to firearms, poaching of Greater One-horned Rhinoceroses in India was reported to have killed as many as 450 rhinos in the ten-year period from 1986 to 1995, and 50 in Nepal over the same interval.
The lessons learned from recovering rhinoceros populations in Nepal offer a comprehensive strategy for long-term conservation. The essential ingredients of the strategy are: strict protection of core areas; powerful economic incentives, and new legislation to promote local guardianship of endangered species and habitats in buffer zones and corridors; effective anti-poaching information networks and anti-poaching units; bold leadership to carry out essential conservation measures such as translocations, fair resettlement of villages located inside reserves, and equitable distribution of ecotourism revenues; and greater conservation awareness at the local level, regarding the uniqueness, rarity, and value of the species. Successful translocations from Chitwan to Dudhwa, Sukla Phanta, and Bardia demonstrate that recovery of rhinoceros populations within their former range in the Terai is possible if the political will can be mustered. A recent conservation action plan for Asian rhinoceroses incorporates these principles into a suite of actions to enhance conservation of the species, built on the success of efforts in Chitwan and Kaziranga. The most preferred habitats of the Greater One-horned Rhinoceros are floodplains, which are also sites of intensive cultivation. The growth of human populations poses a much greater threat to habitat conservation in Asia than in Africa.
If poaching somehow ceased in Africa, rhinoceros populations would increase rapidly, because extensive habitat still remains. Asia presents a different landscape. There is no habitat block that presently contains rhinos in Asia equivalent to the Selous Game Reserve of southern Tanzania, an area roughly the size of Switzerland, or the Kavango-Zambezi Transfrontier landscape (on the borders of Namibia, Angola, Botswana, Zambia, and Zimbabwe, which is the size of Italy (278,000 km2) and constitutes a potential mega-reserve for the Black Rhinoceros. In Asia, rhinoceros sanctuaries are threatened by rapid deforestation and the spread of oil palm and pulp and paper plantations, and human population growth adjacent to protected areas.
Along the continuum of conservation victories and setbacks, the results of conservation efforts undertaken on behalf of the two remaining Asian species have been underwhelming. Today, Javan Rhinos are widely regarded as the most endangered mammals on earth, numbering no more than 30–50 individuals and now restricted to perhaps a single population in Ujung Kulon National Park, in western Java, Indonesia. Prior to the French-Indochina and the Vietnam Wars, a remnant population of Javan Rhinos on the Vietnam border with Cambodia may have contained a larger population than in Java. Hostilities and the aftermath of poaching reduced that population to a few individuals that survived in a degraded forest area outside Cat Tien National Park, called Cat Loc. Efforts to census what were thought to be four remaining individuals, using scent dogs to locate droppings and DNA extraction to sex and identify the remaining individuals, was completed in early 2010. The most recent discovery was the carcass of what might be the last individual in the population, shot by a poacher. The loss of rhinos in Vietnam has sparked a national controversy, and while too late for this population, may motivate the government to protect other endangered species.
Aside from dehorning, the other great debate in rhino conservation is the value of captive breeding as a conservation tool. The debate reached a climax when the Asian Rhino Specialist Group of the IUCN endorsed a proposal to remove Javan Rhinos from Ujung Kulon to an offshore captive facility. The Indonesian government rejected the proposal, to the relief of field biologists. Finally, in 2010, the government was moving closer to translocating some individuals of the Ujung Kulon population to a safe second site in Java, to ward off the possibility of disease, a poaching epidemic, or a violent eruption of nearby Krakatoa decimating the one remaining population.
Once distributed widely across much of South-east Asia and even reaching Assam, India, Sumatran Rhinos experienced a range collapse similar to the Javan Rhino. The decline was so steep, and remaining Sumatran populations so small, that many conservationists now consider this species the most endangered large mammal on earth. The last strongholds of the species are Taman Negara National Park, peninsular Malaysia; the Danum Valley Conservation Area and Tabin Wildlife Refuge in Sabah, Malaysia; and a few reserves in Sumatra (Gunung Leuser, Bukit Barisan Selatan, and Way Kambas National Parks). Nowhere are Sumatran Rhinos common.
One of the great debacles in conservation history involved an effort to save the Sumatran Rhino. A group of western zoos and their Asian counterparts formed the Sumatran Rhino Trust, which in the 1980s undertook to rescue otherwise doomed individuals from natural habitats slated for logging or conversion to oil palm or rubber plantations, to provide a chance for the captured animals to survive, breed, and help maintain the genetic vigor of the population. The ultimate goal of the project was the reestablishment in the wild of descendants of captive-bred animals when "suitable areas were secured." The Sumatran Rhino Trust spent at least US$ 2·5 million to capture 40 doomed individuals, and sent pairs to facilities in Western and Asian zoos. The extent of mortality was shocking, with virtually all the animals dying rather quickly in captivity. One field biologist described this effort in a controversial paper entitled, "Helping a Species To Go Extinct." Eventually, several calves were born at the Cincinnati Zoo. But reproductive rates among wild populations greatly exceeded those in the captive Sumatran Rhino population.
This sad episode forces conservationists to examine the approach they take to saving the most endangered mammals on earth. The first lesson learned is that rhinos, like Tigers, Mountain Gorillas (Gorilla beringei), Giant Pandas (Ailuropoda melanoleuca), and a few other species, are conservation-dependent—they will only survive and recover by direct intervention and management and permanent protection. They are too commercially valuable to poachers and too susceptible to habitat fragmentation and loss to assume that a few years of protection efforts are enough and we can address other problems. The second lesson is that there is no substitute for political will in the conservation of endangered large mammals like rhinoceros. Declaring populations to be doomed and collecting them for captive breeding is a foolish enterprise. In-situ conservation is often cheaper, but it requires the political will of range state leaders to commit to protecting their endangered species and preventing the complete conversion of their forests and extirpation of large mammals. If the five lessons described above could be effectively applied to all remaining rhinoceros populations, the chances for recovery would increase dramatically.
The situation for the Sumatran Rhino in Sabah, a province in northern Borneo and part of the federation of Malaysia, is an important case study of the challenges conservationists face to recover an endangered large mammal. Less than 40 rhinos are believed to survive in Sabah. If half are females, and some females are too old or too young to reproduce, perhaps only six or seven have the potential to give birth. With a birth interval of three years under optimum conditions, no more than two rhinos are being born annually. At this stage, conservationists begin to worry about the Allee effect, a phenomenon whereby a positive correlation exists between individual fitness (survival probability, fertility, reproductive rate) and population density of the species. As numbers of individuals of a species decline to a very low level, various factors associated with very low numbers—narrow genetic base, locally skewed sex ratio, difficulty in finding a fertile mate, reproductive pathology associated with long non-reproductive periods—conspire to drive the numbers even lower. At some point, the death rate eventually exceeds the birth rate, even with adequate habitat and elimination of poaching. In the absence of specific actions to bring Sumatran Rhinos together and boost production of offspring, therefore, there is a strong possibility that the species may go extinct even if protection of its habitats and the remaining individual rhinos can be maintained and improved.
One rhinoceros biologist summed up the recent conservation history with these words: "That there are any free-ranging rhinoceros alive in 2010 is a miracle. That some populations are actually recovering gives hope for many other species of endangered vertebrates. If strict protection and incentives for communities who live near rhinos are effective, endangered species conservation is far from a lost cause but a noble and hopeful occupation for the 21st century."
