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Globally, wildlife populations are becoming increasingly small and isolated. Both processes contribute to an elevated risk of extinction, notably due to genetic factors related to inbreeding depression and a loss of adaptive potential. Wildlife translocation is a valuable conservation tool to reintroduce species to previously occupied areas, or augment existing populations with genetically divergent animals, thereby improving the viability of endangered populations. However, understanding the genetic implications of mixing gene pools is key to avoid the risk of outbreeding depression, and to maximise translocation effectiveness. In this study we used mitochondrial and microsatellite DNA collected from 110 black rhinoceroses (Diceros bicornis minor) in Kruger National Park, South Africa, to determine levels of genetic diversity, inbreeding and relatedness. We compared this diversity with the two source populations (KwaZulu-Natal, South Africa and Zambezi River, Zimbabwe) using data from previously published studies, and assessed changes in the relative contribution of source lineages since their reintroduction in the 1970s. Our results show that Kruger's black rhinoceroses are genetically more diverse than those from KwaZulu-Natal, with levels closer to those from the Zambezi Valley. Furthermore, our findings indicate a relative increase in the Zimbabwean lineage since reintroduction, suggesting a possible selective advantage. From a conservation perspective, our results demonstrate the benefits of mixing multiple source populations to restore gene flow, improve genetic diversity and thereby help protect small, isolated populations from extinction. [ABSTRACT FROM AUTHOR]

Poaching on private land may potentially significantly deplete the rhino population yet is poorly studied. We focus on temporal patterns in poaching events, whether there is any evidence of targeting of specific categories of rhino (in relation to species, sex and age) and whether these patterns in poaching show any trends over time. Using rhino owner and (mainstream and social) media reports, we complied a database of private land poaching events between 2003 and 2017. Patterns in poaching activity were broadly consistent over time. Poaching is most likely at night, under the full moon, and close to the property perimeter. Whilst there was no consistent temporal pattern in poaching, there was evidence of increased poaching during the weekend (Friday–Sunday) compared to weekdays (Monday–Thursday) in 2017. Prioritising rhino protection efforts at these times may therefore be the most efficient use of limited resources. Because there is no evidence that poachers selectively target rhinos, efforts undertaken by private owners to protect specific individuals or groups may be ineffective. Our research also highlighted key data that were currently not clearly recorded, including collateral calf deaths and lost pregnancies, which may have a significant impact on the scale of the rhino poaching problem. [ABSTRACT FROM AUTHOR]

Historical evidence of tuberculosis ( TB) affecting primarily captive rhinoceroses dates back almost two centuries. Although the causative Mycobacterium tuberculosis complex ( MTC) species has not been determined in many cases, especially for those that occurred before bacterial culture techniques were available, the spectrum of documented reports illustrates the importance of TB as cause of morbidity and mortality in different rhinoceros species across continents. In more recent years, sporadic suspected or confirmed cases of TB caused by Mycobacterium bovis ( M. bovis) have been reported in semi-free or free-ranging rhinoceroses in South Africa. However, the true risk TB may pose to the health and conservation of rhinoceros populations in the country's large conservation areas where M. bovis is endemic, which is unknown. Underlying the current knowledge gap is the lack of diagnostic tools available to detect infection in living animals. As documented in other wildlife species, TB could establish itself in a rhinoceros population but remain unrecognized for decades with detrimental implications for wildlife conservation at large and should such animals be moved to uninfected areas or facilities. This paper reviews the current state of knowledge regarding TB in rhinoceros including critical gaps that need to be addressed to effectively assess the threat that this disease may present to rhinoceros. [ABSTRACT FROM AUTHOR]

Ensuring the persistence of populations of endangered species requires an understanding of, and response to, the causes of population declines. Species occurring in small populations are vulnerable to stochastic problems that are environmental, demographic, or genetic in nature and can reduce survival as much as the deterministic threats of habitat degradation. Critically endangered black rhinoceros ( Diceros bicornis) populations declined throughout Africa since 1960, with numbers steadily increasing at a continental level, but remaining lower than three generations ago. However, size, demographics, trends, and factors affecting these, are poorly known. We used 18 years (1990-2008) of long-term sightings data from Ithala Game Reserve, Kwa Zulu- Natal, South Africa, to determine population estimates, growth rate and fecundity over time, as well as sex and age structure and age-specific probabilities of survival. Calf survivorship between the ages of 0 and 1 year was 74% for females and 94% for males. Age-specific survivorship for both sexes was significantly higher from yearling to subadult age-classes (1-6 years) than for adults (7-30 years). The most frequent cause of mortality was attributed to unknown causes while fighting injuries was recorded as the second most common cause of mortality, particularly among subadult and adult males. There was no significant difference in the sex ratios at birth, although the proportion of females in the population was 0.58. There was strong evidence for density-dependent regulation, with density in conception year a key driver of population performance (birth rate). The population does not appear to be at ecological carrying capacity; however, social effects are delaying conception. To mitigate density-dependent social effects, we recommend an adaptive management strategy of pre-selecting individuals for removal from the reserve, so as to maintain stability in the social organization of the population. [ABSTRACT FROM AUTHOR]

To assist with identifying land for reintroduction, a habitat suitability model (HSM) for black rhinoceros (Diceros bicornis) was developed in the arid Augrabies Falls National Park, South Africa, from records of sightings, feeding trails and dung middens. Logistic regression and Bayesian Information Criterion were employed to construct and select the best HSM from >35 eco-geographical variables. The modelled and the observed distributions of black rhinos did not differ (P = 0.323) and k-fold cross-validation confirmed the model's ability to predict the distribution of independent data. The HSM consisted of five variables: availability and equitability of three preferred foods, distance to roads, habitat heterogeneity, slope and shade. The variables 'distance to water' and 'rockiness' were also included in the confidence set of models. Only 50% of the study area had a habitat suitability exceeding 11%, but featured 89% of rhino locations. Of 10 vegetation communities, two with high volumes of favourite foods were preferred. Feeding areas with a high density of preferred food plants were also highly preferred. The riverine vegetation community was not preferred, because its abundant browse was not of the preferred species. The apparent avoidance of roads warrants more research and the attention of park managers. [ABSTRACT FROM AUTHOR]

Small population sizes provide several challenges to conservation managers seeking to ensure species persistence and illustrating conservation success. Black rhinoceros, Diceros bicornis minor, epitomizes these challenges. During October 2008 we used block surveys, estimates of availability and observer bias to calculate landscape-specific black rhino abundances in the southern parts of Kruger National Park, South Africa. We assigned age and sex to individuals, extracted an age distribution, and estimated survival and fecundity given the population growth derived from historical strip transects. The block counts, corrected for 90.3% availability bias with observers missing 3.8% of those, predicted that 627 (95% CI: 588-666) black rhinos resided in the study area. The population increased at 6.75% per annum, the result of high survival and an estimated inter-calving interval of 2.45 years. Age distributions and population growth predicts that subadult males and females have the lowest annual survival, while dependent calves and adults have the highest annual survival. Precise estimates can be obtained with a 20% study area coverage using block counts. This gives coefficient of variances allowing detection of 5% growth from surveys every two years. Detecting 2% annual decline requires bi-annual surveys for 6 years. Our results illustrate that black rhinos are performing well in Kruger National Park. [ABSTRACT FROM AUTHOR]

Black rhinoceros diet and browse availability was investigated in Augrabies Falls (AFNP), Karoo (KRNP) and Vaalbos National Parks (VNP) in South Africa. Rhino tracks were followed and 18,804 standard bite volumes recorded. Browse availability of each plant species was recorded by measuring 14,800 plants and calculating reachable browse volume. The diet comprised 51, 53 and 41 plant species in AFNP, KRNP and VNP, respectively, but three species accounted for more than 65% of the diet in each park, making diet less diverse than available browse in AFNP and KRNP. Browse availability explained 14%, 15% and 52% of diet selection in AFNP, KRNP and VNP, with consumption of most plant species significantly different from availability. A few plant species were so highly preferred that browsing intensities were unsustainable, while some common species were totally rejected. Pressure on the eaten browse averaged 4.4%, 14.5% and 1.3% annually of the volume in AFNP, KRNP and VNP. In the dry season, there was a two to sevenfold increase in browsing pressure on species with actively photosynthesizing tissues. A few key species, including Monechma and Zygophyllum species, were identified as potential early warning indicators of black rhino browsing impact. [ABSTRACT FROM AUTHOR]

Live-harvests from source populations for translocation are key to rapid recovery for many species. Contrary to common assumption, however, reduced density might not immediately improve vital rates because animal recolonization is slow - creating management uncertainty about harvest adequacy or sustainability. Reports measuring animal recolonization are rare. We measured the response of the 19 same- or opposite-sex neighbours of 11 live-harvested black rhinoceros (Diceros bicornis minor) in Hluhluwe-iMfolozi Park, South Africa, by comparing the size and location of their activity areas for an average two years before and after harvest. The only significant change was a decolonization response by opposite-sex neighbours, especially males after the harvest of a female neighbour. Recolonization of habitat after harvest, at least by neighbours, might not just be slow but also further delayed by the disruption of long-standing breeding relationships with important implications for the spatial pattern and frequency of harvest. [ABSTRACT FROM AUTHOR]

Fighting and accidental injury commonly cause black rhinoceros (rhino; Diceros bicornis) death after release. Smaller reserves and higher conspecific density after release (release density) might increase a rhino's encounter rate with hazards like fenced boundaries and conspecifics. We conducted a science-by-management experiment on the influence of reserve size and release density on rates of movement, association, and injury and death amongst 39 black rhinos during the first 100 days after their release into 4 Namibian and 8 South African reserves ranging in size from 670 ha to 45,000 ha. Association rates were negatively related to reserve size and positively correlated with release density. There was also a negative relationship between the proportion of the reserve traversed by individual rhinos and reserve size. In reserves ≥18,000 ha association rates were consistently zero but became elevated in reserves ≤11,500 ha and at release densities ≤9 km²/rhino. Daily displacement did not increase with increasing reserve size >8,500 ha but in smaller reserves daily displacements indicated higher encounter rates by released rhinos with fenced boundaries. Three rhinos received fight-related injuries requiring intervention and 2 of 4 deaths were fight-related. All injuries and 3 deaths occurred in reserves ≤11,500 ha. Model selection based on Akaike's second-order Information Criterion indicated that the parameter release density alone best explained mortality risk. Traditionally considered risk factors, rhino sex, age, and presence of resident conspecifics, were superseded by the risk posed by releases into smaller reserves. Reserves ≤11,500 ha and release densities ≤9 km²/rhino pose an increasing risk to rhino survivorship and so larger reserves and lower densities than these should be favored as release sites. [ABSTRACT FROM AUTHOR]

The Critically Endangered black rhinoceros Diceros bicornis occurs mainly in protected areas. Hluhluwe-Umfolozi Park, South Africa, contains a key source population for black rhino conservation, and declining population productivity has been attributed to negative habitat changes and a reduction in carrying capacity. As home range increase may be an index of declining habitat quality we determined the home ranges of the black rhino in the Park and compared these ranges with previous estimates. The average size of the home ranges during 1991-2001 was 23.07 ± SE 0.81 km², which is 54% greater than in the 1980s. Sex and the availability of water did not influence home ranges. Home ranges decreased in winter. Female:male ratios varied across the Park, indicating that one or both sexes may prefer specific areas. Changes in vegetation structure and composition may have caused rhino to maintain larger ranges in order to meet their nutritional requirements. Ongoing review of stocking rates, population performance (including indicators such as range size), and intervention strategies are necessary to manage black rhino in dynamic savannah ecosystems. [ABSTRACT FROM AUTHOR]