Black Rhinoceros Population Research Articles

Has horn length in an Eastern black rhino population (Diceros bicornis michaeli) decreased over time?

Has horn length in an Eastern black rhino population (Diceros bicornis michaeli) decreased over time?

Antemortem detection of Mycobacterium bovis in nasal swabs from African rhinoceros

Mycobacterium bovis (M. bovis) infection has been identified in black (Diceros bicornis) and white (Ceratotherium simum) rhinoceros populations in Kruger National Park, South Africa. However, it is unknown whether M. bovis infected rhinoceros, like humans and cattle, can shed mycobacteria in respiratory secretions. Limited studies have suggested that rhinoceros with subclinical M. bovis infection may present minimal risk for transmission. However, recent advances that have improved detection of Mycobacterium tuberculosis complex (MTBC) members in paucibacillary samples warranted further investigation of rhinoceros secretions. In this pilot study, nasal swab samples from 75 rhinoceros with defined infection status based on M. bovis antigen-specific interferon gamma release assay (IGRA) results were analysed by GeneXpert MTB/RIF Ultra, BACTEC MGIT and TiKa–MGIT culture. Following culture, speciation was done using targeted PCRs followed by Sanger sequencing for mycobacterial species identification, and a region of difference (RD) 4 PCR. Using these techniques, MTBC was detected in secretions from 14/64 IGRA positive rhinoceros, with viable M. bovis having been isolated in 11 cases, but not in any IGRA negative rhinoceros (n = 11). This finding suggests the possibility that MTBC/M. bovis-infected rhinoceros may be a source of infection for other susceptible animals sharing the environment.

Exploring temperature and precipitation changes under future climate change scenarios for black and white rhinoceros populations in Southern Africa

ABSTRACT Climate change is a potential human-induced threat to rhino populations and their habitat. Information on the effects of climate change on rhinoceros species can help manage and develop conservation plans to adapt to these changes. In this study, two climate change scenarios were used to predict temperature and precipitation changes in national parks in southern Africa and the effect those changes would have on black (Diceros bicornis) and white (Ceratotherium simum) rhinoceros populations. The study used the Intergovernmental Panel on Climate Change (IPCC) Representative Concentration Pathways (RCPs) 4.5 and 8.5, atmospheric CO2 concentrations of 650 and 1370 ppm, for the years 2055 and 2085 to explore the temperature and precipitation changes. All spatial information was processed using Geographic Information Systems and statistical analysis. Results show the changing climate will have significant negative impacts on the probability of occurrence of both species. Temperature changes will affect these probabilities more than precipitation changes. All study parks will have zero probability of occurrence for the species throughout their ranges should conditions reach those represented by the RCP 8.5 scenario late in the century. Conservation activities for the rhinoceros should take into consideration the potential for temperature and precipitation changes modelled in this study.

Probabilistic assessment of the risk of black rhinoceros (Diceros bicornis) species extinction

AbstractThe black rhinoceros (Diceros bicornis), distinguished by its distinctive horned snout and imposing size, stands perilously close to the precipice of extinction. The survival of this majestic species is threatened by a combination of factors, necessitating urgent scientific inquiry into the underlying causes. In this research article, a nonlinear stochastic Ricker model is employed to investigate the challenges faced by the population of black rhinoceros. By integrating innovative mathematical approaches with ecological understanding, the aim is to unravel the intricate dynamics contributing to the endangered status of the black rhino. The critical role of habitat loss and illicit poaching activities in driving the decline of this remarkable species is highlighted by the analysis. These findings emphasise the need for immediate and decisive action to protect the black rhinoceros and mitigate the risk of its extinction. It is imperative that comprehensive conservation efforts be implemented to ensure the long‐term survival of the black rhinoceros and preserve its invaluable place within the ecosystem.

Historical development of the survivorship of zoo rhinoceroses-A comparative historical analysis.

Zoo animal husbandry is a skill that should be developing constantly. In theory, this should lead to an improvement of zoo animal survivorship over time. Additionally, it has been suggested that species that are at a comparatively higher risk of extinction in their natural habitats (in situ) might also be more difficult to keep under zoo conditions (ex situ). Here, we assessed these questions for three zoo-managed rhinoceros species with different extinction risk status allocated by the IUCN: the "critically endangered" black rhino (Diceros bicornis), the "vulnerable" greater one-horned (GOH) rhino (Rhinoceros unicornis), and the "near threatened" white rhino (Ceratotherium simum). Comparing zoo animals ≥1 year of age, the black rhino had the lowest and the white rhino the highest survivorship, in congruence with their extinction risk status. Historically, the survivorship of both black and white rhino in zoos improved significantly over time, whereas that of GOH rhino stagnated. Juvenile mortality was generally low and decreased even further in black and white rhinos over time. Together with the development of population pyramids, this shows increasing competence of the global zoo community to sustain all three species. Compared to the continuously expanding zoo population of GOH and white rhinos, the zoo-managed black rhino population has stagnated in numbers in recent years. Zoos do not only contribute to conservation by propagating ex situ populations, but also by increasing species-specific husbandry skills. We recommend detailed research to understand specific factors responsible for the stagnation but also the general improvement of survivorship of zoo-managed rhinos.

Population parameters, performance and insights into factors influencing the reproduction of the black rhinoceros Diceros bicornis in Namibia

AbstractEstimating the population parameters, performance and factors that influence reproduction from long-term, individual-based monitoring data is the gold standard for effective wildlife management and conservation. Yet this information is often difficult and costly to collect or inaccessible to managers. We synthesized a 20-year set of individual-based monitoring data from a subset of black rhinoceros Diceros bicornis subpopulations across a range of environmental conditions in Namibia. Our findings demonstrate that despite the relatively arid landscape in Namibia, the black rhinoceros metapopulation is performing well, measured by age at first reproduction, inter-birth interval, population growth and survivorship. Information-theoretic modelling revealed that a univariate model including normalized differential vegetative index had a greater influence upon age at first reproduction than population density. The inter-birth interval model set identified cumulative rainfall during the 15 months prior to the birth month as the top model, although the mean normalized differential vegetative index during the inter-birth interval was comparable. There was little evidence for density-dependence effects on reproduction. These findings suggest that although browse quality could have a greater impact on parameters spanning multiple years, shorter-term parameters could be more influenced by rainfall. Our analysis also revealed a synchronous pattern of conceptions occurring in the rainy season. Our study provides a set of population parameter estimates for Namibian black rhinoceros subpopulations and preliminary insights on factors driving their reproduction. These expand our collective knowledge of global black rhinoceros population dynamics and improve our confidence and capability to adaptively manage the black rhinoceros metapopulation of Namibia.

Rhinoceros accounting in Kruger National Park, South Africa

Trends in rhinoceroses (rhinos) in Kruger National Park (Kruger) is of key concern. Poaching drives trends in the Park. Reconciling annual population estimates with yearly reports of poached carcasses fuels public critique. We account for trends in rhinos by extracting time series of estimates. Progressively modelling influences of management introductions and removals, effects of environmental variation and rhino density, direct impacts of poaching, consequences of imperfect carcass detection, and indirect impacts of deaths of dependent calves form the basis of accounting for rhinos. Models that considered all these influences explained 93% of white and 83% of black rhino population trends. In addition, the models predicted 2,515 white and 225 black rhinos, similar to estimates of 2,607 (95% CI: 2,475–2,752) and 202 (95% CI: 172–237) during 2020 respectively. The best model, however, predicts slow recovery with a white rhino population equivalent to pre-poaching achieved between 2030 and 2040. For black rhinos, recovery to pre-poaching population size would be between 2040 and 2050. The poaching onslaught in Kruger disrupted eruptive white rhino dynamics and prevented black rhinos from transitioning into eruptive dynamics. Authorities require innovative approaches within and beyond Kruger to help re-ignite rhino conservation.

Building sustainable ecosystems through community education

Borana Conservancy lies in the Ewaso Nyiro ecosystem in Laikipia County, just north of the Equator in Kenya. Borana, together with its neighbour Lewa Wildlife Conservancy (LWC), is now home to 132 eastern black rhinos (Diceros bicornis michaeli) and 122 southern white rhinos (Ceratotherium simum simum). The population of black rhinos represents at least 13% of Kenya’s black rhino population. Borana’s work revolves around ‘the four Cs’: conservation, community, culture and commerce, showcasing best practices for sustainable living. The long-term goal of the Conservancy is to provide a sustainable ecosystem, in partnership with its neighbours and community, for critically endangered species on the brink of extinction. However, the survival of Borana’s rhinos and other wildlife, is threatened by the unsustainable utilization of natural resources and rangelands across Laikipia County. Expanding human populations are placing significant pressures on these rangelands, exacerbating years of over-utilization and poor management. According to Dr Dino Martins formerly of Mpala Research Centre in Laikipia, livestock stocking rates on many communally owned ranches and conservancies are estimated to be 50 times higher than the recommended ecological carrying capacity (ECC). Many of the current generation of pastoralists believe that the degraded rangelands in their landscape are normal, not realizing that the rangelands should be covered with grass that would retain moisture, sequester carbon, secure water sources, and support biodiversity, if properly utilized and the livestock carrying capacity were reduced to the ideal balance. Although the local schools teach theoretical environmental science, there is no exposure, at a practical level, to how essential intact, functioning ecosystems serve for both humanity and biodiversity. There is an increasing acknowledgement of the value of targeted, practical conservation education programmes in helping communities living adjacent to protected areas (PAs) to develop sustainable livelihoods and allow the effective, long-term conservation of wildlife and ecosystems. The future of Borana Conservancy, and of all PAs across Laikipia, Kenya and Africa as a whole, will depend on people placing a high natural-capital value on conservation and wildlife habitats, and on their having the skills to manage the wider environment in ways that support both human livelihoods and wildlife.

Practical Management of Iron Overload Disorder (IOD) in Black Rhinoceros (BR; Diceros bicornis).

Simple SummaryBlack rhinoceros under human care are predisposed to Iron Overload Disorder that is unlike the hereditary condition seen in humans. We aim to address the black rhino caretaker community at multiple perspectives (keeper, curator, veterinarian, nutritionist, veterinary technician, and researcher) to describe approaches to Iron Overload Disorder in black rhinos and share learnings. This report includes sections on (1) background on how iron functions in comparative species and how Iron Overload Disorder appears to work in black rhinos, (2) practical recommendations for known diagnostics, (3) a brief review of current investigations on inflammatory and other potential biomarkers, (4) nutrition knowledge and advice as prevention, and (5) an overview of treatment options including information on chelation and details on performing large volume voluntary phlebotomy. The aim is to use evidence to support the successful management of this disorder to ensure optimal animal health, welfare, and longevity for a sustainable black rhinoceros population.Critically endangered black rhinoceros (BR) under human care are predisposed to non-hemochromatosis Iron Overload Disorder (IOD). Over the last 30 years, BR have been documented with diseases that have either been induced by or exacerbated by IOD, prompting significant efforts to investigate and address this disorder. IOD is a multi-factorial chronic disease process requiring an evidence-based and integrative long-term approach. While research continues to elucidate the complexities of iron absorption, metabolism, and dysregulation in this species, preventive treatments are recommended and explained herein. The aim of this report is to highlight the accumulated evidence in nutrition, clinical medicine, and behavioral husbandry supporting the successful management of this disorder to ensure optimal animal health, welfare, and longevity for a sustainable black rhinoceros population.

Using N-mixture models to estimate abundance and temporal trends of black rhinoceros (Diceros bicornis L.) populations from aerial counts

Inaccurate estimates of animal populations may lead to flawed management interventions, therefore, it is essential to understand the status and population trend of a species in order to plan its management efficiently. Aerial surveys are considered a useful method for estimating the population size of large conspicuous animals inhabiting large areas, but raw count data from aerial surveys usually underestimate population sizes due to imperfect detection. The use of N-mixture models with aerial count data provides a useful tool to estimate the population sizes while taking detection probability into account. As a study case we used aerial surveys conducted for monitoring black rhinoceros (Diceros bicornis) in Madikwe Game Reserve and Pilanesberg Nature Reserve (South Africa) during 1999–2015, and we analysed data with a dynamic extension of the N-mixture model. We estimated 0.078–0.098 and 0.139–0.142 individuals/km2, respectively, and we found evidence for density dependence in both reserves with a carrying capacity of 0.122 (0.102–0.142) individuals/100 km2. Based on simulations used to assess precision of the estimates, root-mean-square error model (RMSE) estimates was significantly smaller than those for the raw maximum counts.The N-mixture models provide a promising approach to estimate population size, trends and demographic characteristics of large conspicuous mammals such as black rhinoceroses. Such analysis can provide estimates that are more accurate than raw counts. In addition, use of model covariates that affect a species' population parameters can provide useful information for their conservation and management.

Research Article Genetic assessment of a breeding population of black rhinoceros in Kenya using mitochondrial DNA D-loop sequencing

Research Article Genetic assessment of a breeding population of black rhinoceros in Kenya using mitochondrial DNA D-loop sequencing

Testing 'Proportion of Females Calving' as an indicator for population-level reproductive performance for black rhinoceros (Diceros bicornis).

The proportion of females calving (PFC) each year has been employed as an indicator of population reproductive performance in ungulates, especially for species that breed annually, because it requires less detailed population data than inter-birthing intervals and age at first reproduction. For asynchronous breeders with inter-birthing intervals longer than a year such as megaherbivores, however, it is unclear how much annual variation in PFC is expected and whether false signals of density feedback or environmental influence might result from analyzing PFC data. We used census data from a well studied, closed, expanding population of black rhinoceros (Diceros bicornis) to study annual variation in PFC over 22 years. Our analysis of PFC data yielded no false signals of density feedback but weak evidence for an unexpected influence of rainfall. The PFC data exhibited considerable variation, which we attribute to autocorrelation in the time series of PFC data, ‘demographic-founding effects’, changes in stage structure, and demographic stochasticity, some of which the modelling of PFC appears to confuse with an influence of rainfall. We expect such variation to be common in introduced populations and to persist for some years, complicating the interpretation of PFC, though moving averages of PFC can help if employed cautiously. While our analysis does not undermine the possible utility of PFC, the analysis and interpretation of PFC values require care.

Starting small: long‐term consequences in a managed large‐mammal population

AbstractSmall populations are vulnerable to founder effects, stochastic demographic events and inbreeding depression. These factors raise the extinction probability of small populations, and thus effective management plans for endangered species have become essential. The black rhinoceros (Diceros bicornis) survived a historic global population crash and is currently facing renewed threat through poaching, population fragmentation and isolation. South Africa is home to approximately 36% of the world's remaining black rhinos; however, this population is fragmented across parks and reserves, and many of these small populations remain geographically and genetically isolated. The historic population crash, subsequent fragmentation and relentless poaching pressure together threaten the viability of the black rhino population within South Africa. This study employed a practical, non‐invasive sampling protocol and genetic analyses to assess the growth and performance of a small founder population in a fenced reserve. We used these data and recorded life‐history data to compare the population growth and vital rates between the first and second 10‐year periods since founding. We report a decrease in population growth rate and male survival in the second 10‐year period (0.06; 0.89) compared to the first (0.09; 0.97). Genetic diversity (HEXP = 0.405) was low when compared to larger black rhino populations, and average pairwise relatedness was high (0.193). These results suggest that negative genetic consequences and the beginning of density‐dependant growth regulation may be present in this population. This highlights the importance of establishing an evaluation framework for the assessment of small populations of long‐lived mammals in order to inform metapopulation management.

Poaching Detection Technologies—A Survey

Between 1960 and 1990, 95% of the black rhino population in the world was killed. In South Africa, a rhino was killed every 8 h for its horn throughout 2016. Wild animals, rhinos and elephants, in particular, are facing an ever increasing poaching crisis. In this paper, we review poaching detection technologies that aim to save endangered species from extinction. We present requirements for effective poacher detection and identify research challenges through the survey. We describe poaching detection technologies in four domains: perimeter based, ground based, aerial based, and animal tagging based technologies. Moreover, we discuss the different types of sensor technologies that are used in intruder detection systems such as: radar, magnetic, acoustic, optic, infrared and thermal, radio frequency, motion, seismic, chemical, and animal sentinels. The ultimate long-term solution for the poaching crisis is to remove the drivers of demand by educating people in demanding countries and raising awareness of the poaching crisis. Until prevention of poaching takes effect, there will be a continuous urgent need for new (combined) approaches that take up the research challenges and provide better protection against poaching in wildlife areas.

Determining visitor preferences for rhinoceros conservation management at private, ecotourism game reserves in the Eastern Cape Province, South Africa: A choice modeling experiment

South Africa harbours 95% of the world's threatened white rhinoceros (18000) population and 40% of the critically endangered black rhinoceros (1950) population. Increased levels of rhinoceros poaching in South Africa, and the imminent threat of extinction, have emphasized the need for improved management and conservation policies. This study employs a discrete choice experiment in order to value selected supply-side rhinoceros management and conservation strategies at private, ecotourism game reserves in the Eastern Cape Province, South Africa. The valuation setting is couched in real-world management and conservation strategies presently under consideration at state-owned and privately-owned game reserves in South Africa. Results suggest that visitors to these reserves support the sale of stockpiled rhinoceros horn but are strongly opposed to the introduction of trophy hunting or the continuation of rhinoceros darting experiences. Based on the findings of this study, it appears that the choice experiment technique is a promising instrument, which can inform the design of rhinoceros management and conservation policies for privately-owned, ecotourism game reserves in South Africa, with the possibility of extending its use to state-owned nature reserves.

Standardising Home Range Studies for Improved Management of the Critically Endangered Black Rhinoceros.

Comparisons of recent estimations of home range sizes for the critically endangered black rhinoceros in Hluhluwe-iMfolozi Park (HiP), South Africa, with historical estimates led reports of a substantial (54%) increase, attributed to over-stocking and habitat deterioration that has far-reaching implications for rhino conservation. Other reports, however, suggest the increase is more likely an artefact caused by applying various home range estimators to non-standardised datasets. We collected 1939 locations of 25 black rhino over six years (2004–2009) to estimate annual home ranges and evaluate the hypothesis that they have increased in size. A minimum of 30 and 25 locations were required for accurate 95% MCP estimation of home range of adult rhinos, during the dry and wet seasons respectively. Forty and 55 locations were required for adult female and male annual MCP home ranges, respectively, and 30 locations were necessary for estimating 90% bivariate kernel home ranges accurately. Average annual 95% bivariate kernel home ranges were 20.4 ± 1.2 km2, 53 ±1.9% larger than 95% MCP ranges (9.8 km2 ± 0.9). When home range techniques used during the late-1960s in HiP were applied to our dataset, estimates were similar, indicating that ranges have not changed substantially in 50 years. Inaccurate, non-standardised, home range estimates and their comparison have the potential to mislead black rhino population management. We recommend that more care be taken to collect adequate numbers of rhino locations within standardized time periods (i.e., season or year) and that the comparison of home ranges estimated using dissimilar procedures be avoided. Home range studies of black rhino have been data deficient and procedurally inconsistent. Standardisation of methods is required.

Kenmerken van de voortplanting en de geassisteerde voortplanting bij de witte (Ceratotherium simum) en zwarte (Diceros bicornis) neushoorn

De populatie in het wild levende witte en zwarte neushoorns neemt drastisch af, hoofdzakelijk ten gevolge van stroperij en het verlies van de natuurlijke habitat. Geassisteerde voorplanting kan dienen om waardevolle bloedlijnen te behouden en om neushoorns te kweken met als doel de soort in stand te houden en eventueel zelfs terug in het wild te introduceren. Omdat neushoorns moeilijk te benaderen en te onderzoeken zijn, is er nog relatief weinig bekend over de natuurlijke en kunstmatige voortplanting. De neushoorn behoort tot de onevenhoevigen (Perissodactyla), waartoe ook het paard en de tapir behoren. Zodoende kan het paard wellicht het best als model dienen voor het bestuderen van de karakteristieken van de voortplanting en geassisteerde voortplantingstechnieken bij de neushoorn. In dit overzichtsartikel wordt de huidige stand van zaken weergegeven.

Low birth rates and reproductive skew limit the viability of Europe’s captive eastern black rhinoceros, Diceros bicornis michaeli

Ex situ populations play a critical role for the conservation of endangered species, especially where in situ populations face imminent threats. For such populations to act as vital reserves, they must be viable and sustainable. Eastern black rhinoceros (Diceros bicornis michaeli) epitomise the delicate nature of conservation, as a steady increase in the in situ population over the last two decades is threatened to reverse due to intense poaching pressures on rhinoceros across sub-Saharan Africa. This study utilized population viability analysis to evaluate the demographic and genetic viability of the European captive population of eastern black rhinoceros, and compared demographic parameters to in situ reference populations. Although self-sustaining, the ex situ population performs poorly relative to in situ counterparts, growing at a rate of only 1–2 % per annum compared to 6–8 % for managed wild populations. Captive females start reproducing later, have longer inter-calving intervals, and a lower proportion breed each year. Furthermore, over 40 % of reproductive-age animals have yet to reproduce, with additional implications for the maintenance of genetic diversity. Pedigree analysis highlights the unequal contribution of wild-caught founders to the current population; 69 % of which have no living descendants, and more than a third of the current population are related to five founders. This results in a current genome equivalent of just 13.39 equally reproducing founders. Although reproductive skew is not unusual in wild populations, it severely undermines efforts to maintain genetic and phenotypic diversity in captive breeding programmes. We suggest that understanding and alleviating the causes of reproductive skew must be an important consideration for small population management to maintain the genetic and demographic viability of ex situ populations.

Black rhino population dynamics and the hidden cost of poaching at Solio Game Reserve, central Kenya

Black rhino population dynamics and the hidden cost of poaching at Solio Game Reserve, central Kenya

Dynamics of an expanding black rhinoceros (Diceros bicornis minor) population

Understanding population dynamics is critical for meta-population management, especially of endangered species, and also for megaherbivore ecology. We employed complete individual life records to construct census data for a reintroduced black rhinoceros population over 22 years since its founding and investigated its dynamics. Akaike’s information criterion applied to scalar models of population growth based on the generalized logistic unambiguously selected an exponential growth model (r = 0.102 ± 0.017), indicating a highly successful reintroduction. No evidence of density dependence was detected, and thus, we could not confirm the threshold model of density dependence that has influenced black rhinoceros meta-population management. Our analysis supported previous work contending that the generalized logistic is unreliable when fitted to data that do not sample the entire range of population sizes. A stage-based matrix model of the exponential population dynamics exhibited mild transient behaviour. We found no evidence of environmental stochasticity, consistent with our previous studies of this population that found no influence of rainfall on demographic parameters. Demographic stochasticity was present, principally reflected in annual sex-specific recruitment numbers that differed from deterministic predictions of the matrix model. Demographically driven process noise should be assumed to be a component of megaherbivore population dynamics, as these populations are typically relatively small, and should be accounted for in managed removals and introductions. Increase in age at first reproduction with increasing population size, as manifested in the study population, may provide a warning of possible density feedback prior to detectable slowing of population growth rate for megaherbivores.