Poaching of the Black Rhino and Impacts on Tropical Savanna Ecology
Lisa Cobb

Northeastern State University


Introduction


Savannas are unique biomes dominated by grasses. There are extensive savannas in Africa. In addition to serving as important habitat for wildlife, savannas historically serve as important food sources for indigenous human populations. Savanna is used as livestock grazing land for native tribal people and supports hunter/gatherer tribes like the San people of South Africa (Palmer and Ainslie 2002). At the edge of savannas, dry forests abound. These two distinct biomes are held in a careful equilibrium; if the balance is tipped, one will dominate at the expense of the other (Hirota, et. al. 2011). Many pressures are responsible for this unstable habitat distinction. Along with rainfall amounts and fire occurrences, grazing by large herbivores, like the black rhinoceros, influence savanna preservation in that they prevent savanna from converting to forest (2011). Black rhinos, Diceros bicornis, are part of a group of herbivorous megafauna. Of the four black rhinoceros subspecies, one is listed as vulnerable, two are critically endangered, and one is considered extinct by the IUCN (IUCN Red List, Emslie 2012). Poaching is the greatest cause for decline of black rhino species (2012). Loss of these magnificent animals would be a tragedy for the sake of their own preservation. Black rhinoceroses are important in savanna preservation and poaching them to extinction could mean fragmentation and loss of savanna habitat.

Rhino poached in Savé Valley Conservancy. A ranger attempts to find the bullets as evidence.  Photo Courtesy of African Wildlife Conservation Fund.
Rhino poached in Savé Valley Conservancy. A ranger attempts to find the bullets as evidence. Photo Courtesy of African Wildlife Conservation Fund.



















I. Black Rhinoceros (Diceros bicornis) and Sub-species
There are four subspecies of black rhino and each have a different conservation status: Diceros bicornis ssp. bicornis (vulnerable),Diceros bicornis ssp. longipes (extinct), Diceros bicornis ssp. michaeli (critically endangered), andDiceros bicornis ssp. minor (critically endangered) [IUCN].
II. History
The first rhinoceros species walked the Earth 37 million years ago. Since that time, a distinct divergence occurred between rhino species in Africa. In more recent history, about 30,000 years ago, the Asian and European rhinos emerged (Morgan 2010). The black rhino has a historic home range that extended through all of sub-Saharan Africa with the exclusion of the Congo Basin. Today, black rhino populations are located in very small fragments within this range (ADW, Jennifer Kurnit 2009).
black_rhino_map.jpg
A map of Black Rhino inferred historic distribution (yellow) and current distribution (red). Photo courtesy of San Diego Zoo Global. (2003)

III. Life Strategies
Black rhinos typically live 30 to 35 years in the wild. Captive black rhinos can live for 10 to 15 years longer on average. They can grow to weigh between 800 and 1400 kg. They range in length from 3 to 3.75 m (2009). They exhibit a range of skin color and they have have very little hair. They have two horns formed of keratin fibers.

Reproduction
The ordinarily solitary black rhinos come together to mate. Mating can occur at any time of the year. They are polygynous and can mate with multiple partners through their life time. Once successful copulation occurs, the female will have an average gestation period of 15 months or 474 days (2009). Usually, there is one offspring at birth. Rhino offspring are precocial, meaning they are relatively well developed at birth. Infant and juvenile care is solely maintained by the mother. The juvenile will remain dependent on the mother until 4 years of age. Females reach sexual maturity between the ages of 5 and 7. Males reach sexual maturity between the ages of 7 and 8 (2009).

Behavior
Black rhinos are primarily active during early morning and late afternoon. They live a fairly sedentary lifestyle, only becoming active when necessary. They will typically stay close to water, within 25 km. They have also been known to make use of local salt licks (ADW). Ear, tail, head motions, and other physical cues are all part of communication between rhinos. They will spread dung and urinate to mark territory. Males will also scent mark. When individuals come into contact, the outcome depends on the genders making contact. Two females will briefly nudge each other, showing little aggression. A male and female making contact will have a slightly elevated level of aggression. A male will make a certain stiff legged display when courting a female. If she is receptive to copulation she will raise her tail and angle it to the side. If two males come in contact, they become highly aggressive and fight, using their horns as weapons. The less dominant male usually concedes and departs (San Diego Zoo Global 2003).

Foraging Habits
Black rhinos are herbivores. The areas they inhabit show varying degrees of climate and characteristic vegetation from sparse desert to scrubland to grassland to forest. Rhinos tend to congregate more in areas where grassland transitions into forest. Past studies have revealed that they forage extensively on woody plants, especially shrubs and trees of the Acacia genus (Oloo, et. al. 1994). In a study of seasonal foraging habits it was discovered that there was slight variation between seasons on plant forage. In total, 107 species in 37 families were foraged upon. The most heavily browsed families or subfamilies were Acanthaceae, Papilionaceae, Compositae, Euphorbiaceae, Mimosaceae, Verbenaceae, Anacardiaceae, Rhamnaceae. Acacias, belonging to the Mimosaceae family, are the most heavily browsed, during both wet (27%) and dry (36%)seasons (1994). Rhinos often eat the entire plant (1994). This foraging habit effectively reduces woody plants- a pattern that could help maintain grasslands.

IV. Poaching
Black rhinos are poached for their horns. Poaching is the greatest threat to the black rhino. Between the 1970s and 1990s the black rhino population in Africa was reduced by 96% due to illegal poaching (WWF 2013).

Methods
Poachers form organized and heavily armed gangs. They employ a variety of tactics including poaching at night with night vision goggles, firing upon animals from helicopter, darting animals, and use of scopes and silencers (2013). Often, the poachers subdue the rhino with tranquilizers and use a chainsaw or sharp knife to remove the horns (SWNS 2011). They also use spears dipped in anesthesia to immobilize rhinos before killing them. Amateur poachers hack away at the horn, even when the animal is still alive- leaving the animal to die a slow and agonizing death (Patton 2011).

Uses
Black rhino horns are sold on the black market to people in Asian countries who use the rhino horn in various medicines. Proponents of its use in traditional Chinese medicine believe that rhino horn can cure a range of maladies including fever, rheumatism, and gout. It has also been prescribed to treat food poisoning, hallucinations, snake bites, and many more ailments. There is little evidence to support that rhino horn has healing powers (PBS). Demand for rhino horn has increased recently due the unsubstantiated claim that it has cancer curing properties (IUCN). Another reason rhino horns are so highly coveted is that they are used to craft elaborately decorative handles for ceremonial daggers called Jambiyas. The horns used for this purpose are sought by Middle Eastern Muslim men- mostly in Yemen. At the age of 12, boys in Yemen undergo a ceremonial transition into manhood where they are presented with a Jambiya (PBS) . A 2008 report by the Congressional Research Services estimated that illegally traded rhino horn sells for prices ranging from $945 to $50,000 U.S. dollars per kilogram (Patton).

Location
Many African countries have been heavily poached of the native black rhino populations, leaving only fragments behind. The list of countries with marked rhino poaching in past years is long, indeed. It includes: Angola, Cameroon, Central African Republic, Chad, Democratic Republic of the Congo, Mozambique, Namibia, Rwanda, Somalia, Sudan and Uganda (IUCN). Poaching has been greatly enabled by civil unrest, war, and apathetic government stance toward conservation. Currently, remaining rhino populations in Kenya, South Africa, Tanzania, and Zimbabwe are experiencing increased poaching. The majority of black rhinos killed in 2010, 333 of the 378 total, were killed in South Africa(Patton).

Regulation
Many private reserves have employed armed rangers to oversee protection of black rhinos. The unfortunate reality is that many rangers have been equipped with firearms that are unable to match the caliber of weapons used by gangs of poachers (Patton). Many organizations have implemented intelligence gathering networks that provide leads on poaching gangs. Additionally, some rhinos are being tracked with new, advanced transmitters (WWF). Plus, efforts are being made to create a database of rhino horn DNA that will provide forensic evidence in criminal court (WWF). Creation of joint task forces is quite instrumental in regulating poaching. For example, The South African National Joint Operational and Intelligence Structure launched an operation that involves police, national defense force, national parks, Department of Home Affairs, the Department of Environmental Affairs and the Department of International Relations and Cooperation (Patton). Fifteen conservation groups founded the project with goals of improving field rangers training, using better surveillance, increasing legal advocacy, increasing public education, and other methods. For all the efforts made by South African officials and conservation groups, there is still the looming problem presented by Mozambique. Mozambique, one of the world's poorest countries, has no stiff penalties for rhino poaching or horn possession. This allows poachers to cross the border of Mozambique into the Kruger National Park in South Africa. It has been suggested that in some cases rhinos wander across the border into Mozambique (Save the Rhino 2013). In either case, the poachers get little more than a proverbial "slap on the wrist"; their crime is seen only as a misdemeanor in Mozambique (2013).

V. Conservation

Red billed Oxpeckers on a rhino in South Africa. Photo by Lee R. Berger.
Red billed Oxpeckers on a rhino in South Africa. Photo by Lee R. Berger.

Black rhinos need further conservation, even though much progress has been made over the last couple of decades. Black rhinos shape savannas. Their dispersal has an effect on the abundance and type of vegetation in their habitat. To exacerbate complications of maintaining the balance between savanna and forest, poachers often set fire to the savanna to find (rhinos) more easily; the trees survive, the grasses do not (Berkley 2004). To further express their ecological importance, black rhinos also share a mutualistic relationship with oxpecker birds. The birds remove parasites from the rhino's body and, in turn, the birds get a meal. As an additional service, the birds have keener eyesight than the rhinos and, thus, provide them with a warning when a predator is close by (ADW).


Protection
In addition to the regulations mentioned above, a great amount of effort has gone into protecting rhinos. There are many propositions on new methods to further protect rhinos, some of which have already been implemented. In the past, methods have focused on transporting rhinos to a protected or fenced in reserve, monitoring, and patrolling those areas. However, a fair number of poaching incidents are occurring within the confines of these reserves. De-horning rhinos is a newer method being used to deter poachers. There have been mixed results on the success of this technique. When Namibia first used de-horning to deter poachers in the late 1980s to early 1990s, it was very successful. Not one rhino was poached in Namibia during that time (Save the Rhino). Contrarily, in other places, rhinos that have been de-horned were still poached. The consensus is that de-horning must be coupled with other security measures. De-horning has a couple of potential drawbacks- it can pose risks to the rhinos because they must be immobilized and it can be costly (Save the Rhino). Rhino horns grow back over time. With that knowledge, some groups are in favor of legalizing the horn trade. Proponents argue that horns could be humanely harvested without killing the rhino and satisfying consumers in the Asian market (Save the Rhino). There is a great amount of debate concerning one tactic used in protecting rhinos in Asian countries- "shoot to kill." Although it is not typical in Africa to employ this tactic, some people believe it would send a strong message to poachers. Many people feel that there is more value in arresting and prosecuting poachers which could lead to information on poaching operations. The trouble is that there is discrepancy in the punishment for poaching between countries. As an example, in Zambia merely possessing a rhino horn bears the penalty of 20 years in prison, but it Kenya poaching a rhino only bears the penalty of a small fine (Save the Rhino).


Impact on Foraged Plants
In an ideal scenario, black rhinos could remain spread across their native home range browsing on variety of species of plant and securing the structure of savanna edge. The need to preserve rhinos has forced wildlife managers to confine them to certain reserve areas. As a result, the pressure the rhinos place on the plant community in reserves can have a deleterious effect. A study that highlights such animal-plant interaction was performed to assess black rhinos browsing pressure on a threatened species of plant- Euphorbia bothae, at the Great Fish River Reserve (GFRR) in South Africa (Luske and Mertens 2006). Black rhinos have high preference for E. bothae due largely to its succulent properties that allow it to store more water (2006). Luske and Mertens spent 3 years studying rhino browsing of the plants both inside and outside of the reserve. What they discovered was that rhinos reduced plant densities of E. bothae at GFRR, lowered the number of fruiting plants, and reduced the overall height class of plants (2006). They also concluded that rhino browsing failed to serve as a benefit to the plant with formation of more side shoots (2006). Although, other animals browsing on the plant is more detrimental because they consume roots that black rhinos typically do not. More research is needed on new plant recruitment and mortality rates for better management of the reserve biota (Luske and Mertens 2006).


Population Dynamics and Genetics
A great number of black rhino populations are privately owned by stakeholders who serve as custodians to the state (IUCN). Translocation of animals to a reserve presents management issues where genetic diversity is concerned. Inbreeding is a major concern both in reserve settings and in the remaining fragmented wild populations. Management has focused on maintaining a separation of populations (Muya, et. al. 2011). For reserve populations, often a controlled hunt of 5 surplus males annually has been allowed in Namibia and South Africa (IUCN). Overall, most black rhino populations have seen drastically reduced genetic diversity that has lead to further population decline. This is especially true of small populations. The exception is the Kenyan population. A recent genetic study showed that the Kenyan black rhinos maintained high genetic diversity (Muya, et. al.). However, even these rhino populations are at risk of losing diversity due to a recent surge in poaching and habitat destruction (Muya, et. al.).


Extinction Threats
The ultimate failure of our global civilization is the knowledge that humans are directly responsible for extinction of a species. This is the sad reality for one subspecies of black rhino- Diceros bicornis (D.b.) longipes. There were no signs of the rhino in its home state of Cameroon since 2006 and in 2011 it was declared extinct (IUCN). The lowest number of remaining black rhino subspecies is D.b. michaeli with only 799 individuals remaining (Save the Rhino). It may be no coincidence that it is critically endangered given the lack of strict legal penalty in its home state of Kenya (IUCN). Despite the fact that the remaining two subspecies- D. b. bicornis and D. b. minor have seen increase in their populations, they still experience poaching from neighboring states (IUCN). This further exemplifies the fact that rhino poaching is an international problem.


Conclusion

Many studies have demonstrated the ecological importance of black rhinoceroses. The pressure they exert on vegetation is important to their survival, the survival of plant communities, and the indigenous African people. Further investigation of animal-plant interactions is of utmost importance in determining best ways to manage fragmented land and reserves. Poaching threatens all of the aspects of the delicate balance between rhino, savanna, and people. Cooperative government action against poaching that is more uniform and strict, region wide, is needed for further rhino conservation. Reducing demand for rhino horn in international markets requires more international cooperation and education. Although great strides have been made to conserve these remarkable animals, new poaching methods and increased poaching rates are a very current issue that needs resolution so that future extinctions can be prevented.


References

"Rhinoceros. Rhino Horn Use: Fact vs. Fiction."2008. PBS. Nature. Accessed on July 20, 2013 from http://www.pbs.org/wnet/nature/episodes/rhinoceros/rhino-horn-use-fact-vs-fiction/1178/


"Thorny Issues." Thorny Issues. Save the Rhino, n.d. Web. 20 July 2013. http://www.savetherhino.org/rhino_info/thorny_issues.

Amato, et. al. 2013. Black Rhino, Diceros bicornis. San Diego Zoo Global. Accessed July 18, 2013 at http://library.sandiegozoo.org/factsheets/black_rhino/black_rhino.htm


Emslie, R. 2012. Diceros bicornis. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.1. http://www.iucnredlist.org/details/6557/0. Downloaded on 21 July 2013.


Hirota, M., Holmgren, M., Van Nes, E. H., & Scheffer, M. (2011). Global resilience of tropical forest and savanna to critical transitions. Science, 334(14 October 2011), 232-235. Retrieved from http://www.people.fas.harvard.edu/~eebutler/Homepage/Plants_and_Climate_files/Hirota_etal_Science2011.pdf


Illegal poachers hack off rhino horns with chainsaws. (2011, September 15). Southwest News Service. Retrieved from http://swns.com/news/illegal-poachers-hack-off-rhino-horns-with-chainsaws-21184/


Kurnit, J. 2009. "Diceros bicornis" (On-line), Animal Diversity Web. Accessed July 20, 2013 at http://animaldiversity.ummz.umich.edu/accounts/Diceros_bicornis/


Lewis, M. (n.d.). Black Rhino. WWF. Retrieved on July 18, 2013 from http://worldwildlife.org/species/black-rhino


Luske, B., & Mertens, T. (2006). Impact of black rhinoceros (diceros bicornis minor) on a local population of euphoriba bothae in the great fish river reserve, south africa. Manuscript submitted for publication, Resource Ecology Group, Wengen University and University of Forte Hare, Netherlands and South Africa. Retrieved from http://bokiluske.com/publications/2006 Impact of black rhinoceros (Diceros bicornis minor) on a local population of Euphorbia bothae in the Great Fish River Reserve, South Africa.pdf


Morgan, S. (2010). Black rhinoceros (diceros bicornis) habitat selection and movement analysis. (Doctoral dissertation, Unive rsity of KwaZulu - Natal)Retrieved from http://www.rhinoresourcecenter.com/pdf_files/134/1341268629.pdf


Muya, S. M., Bruford, M. W., Muigai, A. W. -., Oseimo, Z. B., Mwachiro, E., Okita-Ouma, B., & Goossens, B. (2011). Substantial molecular variation and low genetic structure in kenya’s black rhinoceros: implications for conservation. Manuscript submitted for publication, , Available from Conservation Genetics. (10.1007/s10592-011-0256-3) Retrieved from http://www.rhinoresourcecenter.com/pdf_files/132/1320463762.pdf


Oloo, T. W., Brett, R., & Young, T. P. (1994). Seasonal variation in the feeding ecology of black rhinoceros (diceros bicornis l.) in laikipia, kenya. African Journal of Ecology, 32, 142-157. Retrieved from http://www.rhinoresourcecenter.com/pdf_files/124/1246006556.pdf


Palmer, T., & Ainslie, A. (2006, August). South africa. Retrieved from http://www.fao.org/ag/AGP/AGPC/doc/Counprof/southafrica/southafrica.htm


Patton, Dr., F. (2011). The war for rhinos. Manuscript submitted for publication, Department of War Studies, Kings College, London, UK. Retrieved from http://www.rhinoresourcecenter.com/pdf_files/133/1333274767.pdf


The grassland biome. Informally published manuscript, Museum of Paleontology, University of California Berkley, Berkley, California, Retrieved from http://www.ucmp.berkeley.edu/glossary/gloss5/biome/grassland.html