Diceros Research Articles

Effects of dehorning on population productivity in four Namibia sub-populations of black rhinoceros (Diceros bicornis bicornis)

The black rhinoceros (rhino) (Diceros bicornis) is critically endangered, with poaching being one of several threats to the species’ survival. Many reserves across several countries, including Namibia, South Africa, and Zimbabwe, now dehorn their rhinos in an attempt to reduce poaching. Historical data collected by the Namibian Ministry of Environment, Forestry, and Tourism and Save the Rhino Trust were used to investigate whether dehorning has an effect on age at first reproduction (AFR), inter-calving interval (ICI), birth sex ratios, calf survival, cause of death, and lifespan. These were assessed in four Namibian sub-populations (hereafter referred to as ‘populations’) of black rhino (denoted A, B, C, and D) which have undergone varying levels of dehorning. No significant difference was found in any of the variables between dehorned and horned individuals. Population was a significant predictor of AFR (LRT = 7.433, p = 0.024) and ICI (LRT = 13.281, p = 0.004), although pairwise comparisons only found populations A and B to be significantly different (AFR: z = −2.736, p = 0.017, ICI: z = −3.705, p = 0.001). Additionally, a significantly higher number of males than females were born in population D (p = 0.021, CI = 0.544, 0.960). The main cause of death across all individuals was poaching, although there was no significant difference in the proportion of rhinos poached between dehorned and horned individuals (X2 = 0.638, p = 0.424, n = 265). No evidence was found to suggest that dehorning has any effect on AFR, ICI, birth sex ratios, calf survival, or lifespan in the black rhino, which is reassuring in the continued use of dehorning as an anti-poaching technique in this species.

Protecting endangered megafauna through AI analysis of drone images in a low-connectivity setting: a case study from Namibia.

Assessing the numbers and distribution of at-risk megafauna such as the black rhino (Diceros bicornis) is key to effective conservation, yet such data are difficult to obtain. Many current monitoring technologies are invasive to the target animals and expensive. Satellite monitoring is emerging as a potential tool for very large animals (e.g., elephant) but detecting smaller species requires higher resolution imaging. Drones can deliver the required resolution and speed of monitoring, but challenges remain in delivering automated monitoring systems where internet connectivity is unreliable or absent. This study describes a model built to run on a drone to identify in situ images of megafauna. Compared with previously reported studies, this automated detection framework has a lower hardware cost and can function with a reduced internet bandwidth requirement for local network communication. It proposes the use of a Jetson Xavier NX, onboard a Parrot Anafi drone, connected to the internet throughout the flight to deliver a lightweight web-based notification system upon detection of the target species. The GPS location with the detected target species images is sent using MQ Telemetry Transport (MQTT), a lightweight messaging protocol using a publisher/subscriber architecture for IoT devices. It provides reliable message delivery when internet connection is sporadic. We used a YOLOv5l6 object detection architecture trained to identify a bounding box for one of five objects of interest in a frame of video. At an intersection over union (IoU) threshold of 0.5, our model achieved an average precision (AP) of 0.81 for black rhino (our primary target) and 0.83 for giraffe (Giraffa giraffa). The model was less successful at identifying the other smaller objects which were not our primary targets: 0.34, 0.25, and 0.42 for ostrich (Struthio camelus australis), springbok (Antidorcas marsupialis) and human respectively. We used several techniques to optimize performance and overcome the inherent challenge of small objects (animals) in the data. Although our primary focus for the development of the model was rhino, we included other species classes to emulate field conditions where many animal species are encountered, and thus reduce the false positive occurrence rate for rhino detections. To constrain model overfitting, we trained the model on a dataset with varied terrain, angle and lighting conditions and used data augmentation techniques (i.e., GANs). We used image tiling and a relatively larger (i.e., higher resolution) image input size to compensate for the difficulty faced in detecting small objects when using YOLO. In this study, we demonstrated the potential of a drone-based AI pipeline model to automate the detection of free-ranging megafauna detection in a remote setting and create alerts to a wildlife manager in a relatively poorly connected field environment.

Safety and efficacy of a novel iron chelator (HBED; (N,N'-Di(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid)) in equine (Equus caballus) as a model for black rhinoceros (Diceros bicornis).

While iron overload disorder (IOD) and related disease states are not considered a common occurrence in domestic equids, these issues appear prevalent in black rhinoceroses under human care. In addressing IOD in black rhinos, altering dietary iron absorption and excretion may be the most globally practical approach. A main option for treatment used across other species such as humans, is chelation therapy using iron‐specific synthetic compounds. As horses may serve as an appropriate digestive model for the endangered rhinoceros, we evaluated the potential use of the oral iron chelator N,N‐bis(2‐hydroxybenzyl)ethylenediamine‐N,N‐diacetic acid (HBED) in horses for safety and efficacy prior to testing in black rhinoceros. Health and iron digestibility and dynamics were assessed in horses (n = 6) before, and after treatment with HBED (50 mg/kg body weight) for 8 days using a crossover design with serum, faecal and urine collection. A preliminary pharmacokinetic trial was also performed but no trace of HBED was found in serially sampled plasma through 8 h post‐oral dosing. HBED increased urinary iron output in horses compared to control by 0.7% of total iron intake (p < 0.01), for an average of 27 mg urinary iron/day, similar to human chelation goals. Blood chemistry, blood cell counts and overall wellness were not affected by treatment. As healthy horses are able to regulate iron absorption, the lack of change in iron balance is unsurprising. Short‐term HBED administration appeared to be safely tolerated by horses, therefore it was anticipated it would also be safe to administer to black rhinos for the management of iron overload.

ASSESSMENT OF CAPILLARY ZONE ELECTROPHORESIS AND SERUM AMYLOID A QUANTITATION IN CLINICALLY NORMAL AND ABNORMAL SOUTHERN WHITE RHINOCEROS (CERATOTHERIUM SIMUM SIMUM) AND SOUTHERN BLACK RHINOCEROS (DICEROS BICORNIS MINOR).

Capillary zone electrophoresis (CZE) and an immunoassay for serum amyloid A (SAA) were used to examine serum samples from clinically normal and abnormal southern white rhinoceros (Ceratotherium simum simum) and southern black rhinoceros (Diceros bicornis minor) under managed care. CZE resolved seven fractions as well as subfractions for α1 globulins. Reference intervals were calculated for white rhinoceros (n = 33) and found to have some differences over previously reported intervals generated using agarose gel electrophoresis (AGE) methods in sera from free-ranging animals. In addition, the coefficient of variation related to fraction quantitation was found to be overlapping or superior to that reported for AGE. No significant differences were observed in CZE measurands and total protein between clinically normal and abnormal rhinoceros. In contrast to CZE, significant differences in SAA levels (P < 0.001) were observed in samples from the white rhinoceros between clinically normal and abnormal animals. In addition, in limited sample sets with repeated measures, SAA provided prognostic value. Future studies should generate more robust reference intervals and delineate the application of both SAA quantitation and CZE in routine health assessments and in prognostication.

Epidemiology of Mycobacterium bovis infection in free-ranging rhinoceros in Kruger National Park, South Africa

Mycobacterium bovis infection, which is a prominent cause of bovine tuberculosis, has been confirmed by mycobacterial culture in African rhinoceros species in Kruger National Park (KNP), South Africa. In this population-based study of the epidemiology of M. bovis in 437 African rhinoceros (Diceros bicornis, Ceratotherium simum), we report an estimated prevalence of 15.4% (95% CI: 10.4 to 21.0%), based on results from mycobacterial culture and an antigen-specific interferon gamma release assay from animals sampled between 2016 and 2020. A significant spatial cluster of cases was detected near the southwestern park border, although infection was widely distributed. Multivariable logistic regression models, including demographic and spatiotemporal variables, showed a significant, increasing probability of M. bovis infection in white rhinoceros based on increased numbers of African buffalo (Syncerus caffer) herds in the vicinity of the rhinoceros sampling location. Since African buffaloes are important maintenance hosts for M. bovis in KNP, spillover of infection from these hosts to white rhinoceros sharing the environment is suspected. There was also a significantly higher proportion of M. bovis infection in black rhinoceros in the early years of the study (2016–2018) than in 2019 and 2020, which coincided with periods of intense drought, although other temporal factors could be implicated. Species of rhinoceros, age, and sex were not identified as risk factors for M. bovis infection. These study findings provide a foundation for further epidemiological investigation of M. bovis, a multihost pathogen, in a complex ecosystem that includes susceptible species that are threatened and endangered.

Effects of age and sex on site fidelity, movement ranges and home ranges of white and black rhinoceros translocated to the Okavango Delta, Botswana

AbstractEvaluating translocation success is essential for wildlife management and conservation; short‐term success can be evaluated by analysing settlement behaviour after release. We analysed GPS collar data from 47 white (Ceratotherimum simum simum, Burchell, 1817) and 25 black (Diceros bicornis minor, Drummond, 1876) rhinoceros translocated to the Okavango Delta in Botswana between 2014 and 2018. We tested for effects of age and sex on site fidelity and compared movement ranges after translocations between different release sites and between newly released and established individuals. White rhinoceros adults displayed higher site fidelity than subadults and males higher than females. Adults may therefore be better translocation candidates. Site fidelity of black rhinoceros did not differ between sexes or ages. Established rhinoceros movement ranges were smaller than those of newly released ones, pointing towards extended post‐translocation exploratory movements and later settlement in smaller home ranges. Movement ranges of white rhinoceros released on an island were significantly smaller than others, which shows together with annual home range sizes compared with the literature that reserve size and rhinoceros density affect home range size. All rhinoceros in this study survived for more than 1‐year post‐translocation, so these translocations can be deemed successful in the short term.

Female reproductive skew exacerbates the extinction risk from poaching in the eastern black rhino.

Variation in individual demographic rates can have large consequences for populations. Female reproductive skew is an example of structured demographic heterogeneity where females have intrinsic qualities that make them more or less likely to breed. The consequences of reproductive skew for population dynamics are poorly understood in non-cooperatively breeding mammals, especially when coupled with other drivers such as poaching. We address this knowledge gap with population viability analyses using an age-specific, female-only, individual-based, stochastic population model built with long-term data for three Kenyan populations of the Critically Endangered eastern black rhino (Diceros bicornis michaeli). There was substantial reproductive skew, with a high proportion of females not breeding or doing so at very low rates. This had a large impact on the projected population growth rate for the smaller population on Ol Jogi. Moreover, including female reproductive skew exacerbates the effects of poaching, increasing the probability of extinction by approximately 70% under a simulated poaching pressure of 5% offtake per year. Tackling the effects of reproductive skew depends on whether it is mediated by habitat or social factors, with potential strategies including habitat and biological management respectively. Investigating and tackling reproductive skew in other species requires long-term, individual-level data collection.

The effects of fire frequency on vegetation structure and mammal assemblages in a savannah‐woodland system

AbstractFire frequency affects vegetation structure and composition in savannah‐ woodlands, with the potential indirect consequence of affecting the habitat choice and space use of large mammals. Understanding these responses can assist with the development of appropriate fire management policies to conserve co‐existing species with different habitat requirements. In a natural experiment in Majete Wildlife Reserve, Malawi, we compared vegetation composition, woody plant structure and large (&gt;5 kg) mammal assemblages on 10 frequently and 10 infrequently burnt 30‐ha plots, that had fire return intervals of &lt;2.5 and &gt;6 years, respectively, between 2001 and 2019. Fire frequency had little effect on woody plant composition, but did affect grass species composition. Frequent burning reduced mean tree height from 4 to 3 m, woody plant cover from 59% to 35%, and resulted in the dominance of short‐statured, less‐palatable grasses. Many mammal species showed clear preferences for either frequently burnt (e.g. buffalo, zebra, kudu, impala and sable) or infrequently burnt (e.g. nyala, bush pig, baboon, common duiker and vervet monkey) areas, while others (e.g. elephants and black rhinoceros) were not selective. We conclude that establishing a mosaic of patches exposed to different fire frequencies would allow for the persistence of all mammal species in the area by creating an optimal range of habitat types.

Combatting Climate Change, Supporting Biodiversity Conservation and Benefitting Local People at Mombo, Okavango Delta, Botswana

Abstract Mombo Camp is located on Chief’s Island in the Moremi Game Reserve within the Okavango Delta of Botswana. This case study explains how the camp has dramatically reduced its carbon emissions by converting its power from diesel generators to 100% solar energy, and made substantial contributions to black and white rhino re-introductions in the country. Through its lease fees, employment, and procurement, the lodge has also made substantial contributions to the local and national economy during the course of its concession period. Information Snyman, S. and Spenceley, A. (2019) Private Sector Tourism in Conservation Areas in Africa, CABI © CAB International 2022

Rhinoceros serum labile plasma iron and associated redox potential: interspecific variation, sex bias and iron overload disorder disconnect.

A consequence of the poaching crisis is that managed rhinoceros populations are increasingly important for species conservation. However, black rhinoceroses (BR; Diceros bicornis) and Sumatran rhinoceroses (SR; Dicerorhinus Sumatrensis) in human care often store excessive iron in organ tissues, a condition termed iron overload disorder (IOD). IOD research is impeded by the challenge of accurately monitoring body iron load in living rhinoceroses. The goals of this study were to (i) determine if labile plasma iron (LPI) is an accurate IOD biomarker and (ii) identify factors associated with iron-independent serum oxidative reduction potential (ORP). Serum (106 samples) from SRs (n = 8), BRs (n = 28), white rhinoceros (n = 24) and greater one-horned rhinoceros (GOH; n = 16) was analysed for LPI. Samples from all four species tested positive for LPI, and a higher proportion of GOH rhinoceros samples were LPI positive compared with those of the other three species (P < 0.05). In SRs, the only LPI-positive samples were those from individuals clinically ill with IOD, but samples from outwardly healthy individuals of the other three species were LPI positive. Serum ORP was lower in SRs compared with that in the other three species (P < 0.001), and iron chelation only reduced ORP in the GOH species (P < 0.01; ~5%). Serum ORP sex bias was revealed in three species with males exhibiting higher ORP than females (P < 0.001), the exception being the SR in which ORP was low for both sexes. ORP was not associated with age or serum iron concentrations (P ≥ 0.05), but was positively correlated with ferritin (P < 0.01). The disconnect between LPI and IOD was unanticipated, and LPI cannot be recommended as a biomarker of advanced rhino IOD. However, data provide valuable insight into the complex puzzle of rhinoceros IOD.

Why are some animals popular with wildlife tourists: insights from South Africa

ABSTRACT Wildlife tourism is an important type of ecotourism including in South Africa. We considered how the aesthetic value theory can be applied to wildlife tourism by assessing the relative popularity of species with tourists in South Africa and which traits predicted popularity. When data from six published visitor surveys across seven protected areas were combined, we found that only 26 species out of 299 mammals and 850 + birds were selected by 2245 tourists. Elephant (48%), black and white rhinos (36%), lion (36%), cheetah (35%) and giraffe (34%) were the most popular in these visitor surveys with similar results reported in data from destination marketing and social media, but not wildlife auctions. When 13 species traits were assessed using ordinations and Generalised Linear Models, traits associated with specific aesthetics were important as large mammals that use open vegetation, with highly contrasting coat colours and/or are fluffy were most popular. Given the diversity of animals in South Africa, those responsible for wildlife tourism opportunities could diversify the types of species used in marketing to better match animals likely to be encountered in the wild, enhancing repeat visitor experiences while promoting the conservation of more species in the region.

Rhinoceros Serum microRNAs: Identification, Characterization, and Evaluation of Potential Iron Overload Biomarkers.

Iron overload disorder (IOD) in critically endangered Sumatran (Dicerorhinus sumatrensis) and black (Diceros bicornis) rhinoceros is an over-accumulation of iron in organs which may exacerbate other diseases and indicate metabolic disturbances. IOD in rhinos is not well understood and diagnostics and therapeutics are limited in effectiveness. MicroRNAs (miRNAs) are small non-coding RNAs capable of altering protein synthesis. miRNA expression responds to physiological states and could serve as the basis for development of diagnostics and therapeutics. This study aimed to identify miRNAs differentially expressed among healthy rhinos and those afflicted with IOD or other diseases (“unhealthy”), and assess expression of select miRNAs to evaluate their potential as biomarkers of IOD. miRNAs in serum of black (n = 11 samples; five individuals) and Sumatran (n = 7 samples; four individuals) rhinos, representing individuals categorized as healthy (n = 9), unhealthy (n = 5), and afflicted by IOD (n = 3) were sequenced. In total, 715 miRNAs were identified, of which 160 were novel, 131 were specific to black rhinos, and 108 were specific to Sumatran rhinos. Additionally, 95 miRNAs were specific to healthy individuals, 31 specific to unhealthy, and 63 were specific to IOD individuals. Among healthy, unhealthy, and IOD states, 21 miRNAs were differentially expressed (P ≤ 0.01). Five known miRNAs (let-7g, miR-16b, miR-30e, miR-143, and miR-146a) were selected for further assessment via RT-qPCR in serum from black (n = 61 samples; seven individuals) and Sumatran (n = 38 samples; five individuals) rhinos. let-7g, miR-30e, and miR-143 all showed significant increased expression (P ≤ 0.05) during IOD (between 1 and 2 years prior to death) and late IOD (within 1 year of death) compared to healthy and unhealthy individuals. miR-16b expression increased (P ≤ 0.05) in late IOD, but was not different among IOD, healthy, and unhealthy states (P > 0.05). Expression of miR-146a increased in IOD and late IOD as compared to unhealthy samples (P ≤ 0.05) but was not different from the healthy state (P > 0.05). Selected serum miRNAs of black and Sumatran rhinos, in particular let-7g, miR-30e, and miR-143, could therefore provide a tool for advancing rhino IOD diagnostics that should be further investigated.

Cardiopulmonary Parameters and Arterial Blood Gases During Etorphine-Medetomidine-Midazolam Immobilization in Free-Ranging Black Rhinoceroses (Diceros bicornis) Undergoing Electro-Ejaculation-A Preliminary Study.

Conservation management interventions for the critically endangered black rhinoceros (Diceros bicornis) require immobilization, which offer opportunities for semen collection and cryopreservation to establish genetic reservoirs. In free-ranging rhinoceroses, a combination of the potent opioid etorphine and the tranquilizer azaperone is routinely used for chemical immobilization but is associated with muscle rigidity and severe cardiopulmonary changes. Additionally, azaperone inhibits semen emission. Seven free-ranging, male, sexually mature black rhinoceroses were immobilized with an alternative protocol consisting of 4.5 mg etorphine, 5 mg medetomidine, 50 mg midazolam and 2,500 IU hyaluronidase delivered remotely by darting from a helicopter. During the immobilization, electro-ejaculation was performed with a portable electro-ejaculator, and a species-specific rectal probe. Animals were observed for muscle tremors. Longitudinal changes in respiratory rate, heart rate and peripheral oxyhemoglobin saturation, measured at 5 min intervals, were assessed using a general mixed model. Non-invasive oscillometric blood pressure and arterial blood gas variables were measured at first handling and before reversal and compared using the Wilcoxon rank sum test. All animals were successfully immobilized, showed no muscle tremors, presented with normal heart rates and lactate concentration (<5 mmol/L), recovered uneventfully, but experienced acidemia, hypoxemia and hypercapnia. Induction time and total time in recumbency were 4.2 ± 0.41 and 38.4 ± 6.9 min, respectively. Electro-stimulation commenced after 11.7 ± 3.98 min and completed after 24.3 ± 6.65 min. Semen-rich fractions were successfully collected from six animals. Our observations indicate that etorphine-medetomidine-midazolam provides a promising immobilization protocol for free-ranging black rhinoceroses, that allows for successful electro-ejaculation.

Fighting for their survival

The International Rhino Foundation (IRF), based in the United States operates on-the-ground programmes in Africa and Asia where rhinos live in the wild, supporting viable populations of the five remaining rhino species and the communities that coexist with them. Through grants and field programmes, IRF has funded rhino conservation efforts in 10 countries, focusing on scientific research, anti-poaching, habitat conservation, captive breeding, environmental education, and demand reduction strategies. Over the last decade more than $20 million has been invested in rhino conservation. The organization was founded by concerned individuals in response to intense poaching of Zimbabwe’s black rhinos in the early 1990s. IRF with supporters and partners helped to virtually eliminate the threat and stabilize the population there. To this day, we support conservation programmes in Zimbabwe and IRF has expanded to support all five species of rhinos. IRF prioritizes collaboration. Through a network of hundreds of conservation organizations, private foundations, corporations, government agencies and individuals all over the world, we achieve common goals for rhinos together. We are Team Rhino. IRF listens to local communities living in close proximity to rhino populations. Working together, we participate in mutually beneficial partnerships through wildlife conservation. A key objective is to build a unified front to save rhinos by engaging and activating the many people around the world who are as concerned as we are about the rhino. Our global team of rhino conservationists is calling for an end to rhino poaching and sharing the plight of the rhino with others.

The Impact of COVID-19 Government Responses on Rhinoceroses in Kruger National Park

Global COVID-19 responses by governments restricted international travel, imposed national lockdowns, reduced economies, and influenced people's livelihoods. Travel restrictions and national lockdowns may constrain international illegal supply chains of high value wildlife products such as rhinoceros (rhino) horn. We evaluated whether the COVID-19 lockdown responses by South Africa induced a poaching pause on rhinos in Kruger National Park. We collated information on poaching incidences from 2017 and made predictions for expected incidences during 2020 using trends noted between 2017 and 2019. Rangers observed substantially fewer incidences of poaching during South Africa's hard lockdown. As restrictions eased, poaching incidences increased. Despite the COVID-19 poaching pause, both black and white rhinos continued to decline in Kruger National Park as recruitment could not offset poaching and natural deaths.

Persuading the Implicit Mind: Changing Negative Implicit Evaluations With an 8-Minute Podcast

Implicit evaluations can be malleable via reinterpretation of previously encountered evidence. Here, we report three studies (N = 1,007) investigating the robustness of this updating modality using ecologically realistic materials. Participants were first introduced to a target who killed an endangered black rhino in Namibia. They then listened to a real podcast providing counterattitudinal information on the benefits of trophy hunting. The podcast resulted in considerable revisions of initially negative implicit evaluations toward positivity, consistently across implicit measures (affect misattribution procedures vs. implicit association test), samples (American students vs. nonstudents from various countries), study settings (lab vs. online), and the presence versus absence of a memory retrieval manipulation prompting reflection on participants’ views on trophy hunting. Taken together, these findings suggest that reinterpretation can shift implicit evaluations of even highly negative targets, including under conditions of external validity.

Integrating Nguni cattle into black rhino reserves: Could this be a novel rural community-based conservation model?

Integrating Nguni cattle into black rhino reserves: Could this be a novel rural community-based conservation model?

Indirect effects of African megaherbivore conservation on bat diversity in the world's oldest desert.

In extreme environments, temperature and precipitation are often the main forces responsible for structuring ecological communities and species distributions. The role of biotic interactions is typically thought to be minimal. By clustering around rare and isolated features, like surface water, however, effects of herbivory by desert-dwelling wildlife can be amplified. Understanding how species interact in these environments is critical to safeguarding vulnerable or data-deficient species. We examined whether African elephants (Loxodonta africana), black rhinoceros (Diceros bicornis), and southern giraffe (Giraffa giraffa) modulate insectivorous bat communities around permanent waterholes in the Namib Desert. We estimated megaherbivore use of sites based on dung transects, summarized vegetation productivity from satellite measurements of the normalized difference vegetation index, and surveyed local bat communities acoustically. We used structural equation models to identify relationships among megaherbivores and bat species richness and dry- (November 2016-January 2017) and wet- (February-May 2017) season bat activity. Site-level megaherbivore use in the dry season was positively associated with bat activity-particularly that of open-air foragers-and species richness through indirect pathways. When resources were more abundant (wet season), however, these relationships were weakened. Our results indicate that biotic interactions contribute to species distributions in desert areas and suggest the conservation of megaherbivores in this ecosystem may indirectly benefit insectivorous bat abundance and diversity. Given that how misunderstood and understudied most bats are relative to other mammals, such findings suggest that managers pursue short-term solutions (e.g., community game guard programs, water-point protection near human settlements, and ecotourism) to indirectly promote bat conservation and that research includes megaherbivores' effects on biodiversity at other trophic levels.

Volumetric Body Mass Estimate and in vivo Reconstruction of the Russian Pareiasaur Scutosaurus karpinskii

Pareiasaurs (Amniota, Parareptilia) were characterized by a global distribution during the Permian period, forming an important component of middle (Capitanian) and late Permian (Lopingian) terrestrial tetrapod biodiversity. This clade represents an early evolution of sizes over a ton, playing a fundamental role in the structure of middle and late Permian biodiversity and ecosystems. Despite their important ecological role and relative abundance around the world, our general knowledge of the biology of these extinct tetrapods is still quite limited. In this contribution we provide a possiblein vivoreconstruction of the largest individual of the speciesScutosaurus karpinskiiand a volumetric body mass estimate for the taxon, considering that body size is one of the most important biological aspects of organisms. The body mass ofScutosauruswas calculated using a 3D photogrammetric model of the complete mounted skeleton PIN 2005/1537 from the Sokolki locality, Arkhangelsk Region, Russia, on exhibit at the Borissiak Paleontological Institute, Russian Academy of Sciences (Moscow). By applying three different densities for living tissues of 0.99, 1, and 1.15 kg/1,000 cm3to reconstructed “slim,” “average” and “fat” 3D models we obtain average body masses, respectively, of 1,060, 1,160, and 1,330 kg, with a total range varying from a minimum of one ton to a maximum of 1.46 tons. Choosing the average model as the most plausible reconstruction and close to the natural condition, we consider a body mass estimate of 1,160 kg as the most robust value forScutosaurus, a value compatible with that of a large terrestrial adult black rhino and domestic cow. This contribution demonstrates that barrel-shaped herbivores, subsisting on a high-fiber diet and with a body mass exceeding a ton, had already evolved in the upper Palaeozoic among parareptiles, shedding new light on the structure of the first modern terrestrial ecosystems.

Effect of high population density of eastern black rhinoceros, a mega‐browser, on the quality of its diet

AbstractHigh density of herbivore populations can lead to intense foraging competition and depletion of food consequently lowering diet quality and population performance. We tested for the effects of the density of eastern black rhinoceros (Diceros bicornis michaeli) in ninein situpopulations of 0.01–0.7 individuals per km2density range on the quality of their diet while controlling for plant available moisture and plant available nutrients. We used faecal calcium, phosphorus, copper and zinc concentrations as proxy indices for dietary quality from 473 fresh faecal samples obtained from 77 adult animalsin situ, after determining a positive faeces‐diet mineral correlation in feeding trials with black rhinoceros in zoos. Some populations surpassed 70%–80% of their estimated maximum stocking densities expected to cause impact on forage. However, we did not find significant correlation between rhino population density and dietary quality, as measured via faecal mineral nutrient content. This suggests that black rhinoceros may have sufficient behavioural plasticity to adjust their diet to cover their nutritional requirements when density increases. Instead, 1‐month lagged plant available moisture, reflecting precipitation over the 4 weeks preceding each sampling effort, significantly explained the mineral concentrations in the faeces. By contrast, plant available nutrients had no effect.