Handheld point-of-care blood analyzers deliver rapid results for biochemical and hematologic parameters, making them very useful in veterinary clinics and in fieldwork applications. This study compared the biochemical and hematologic parameters generated by the novel point-of-care analyzer i-STAT® Alinity V CHEM8+ cartridge between human-managed and free ranging populations of southern white rhinoceros (Ceratotherium simum simum). In addition, a novel reference interval for ionized calcium (iCa), a parameter of diagnostic and prognostic importance, was established for southern white rhinoceros. Blood samples were obtained from 10 managed (6 at NC Zoo and 4 at Busch Gardens Tampa Bay in 2019) and 30 free ranging white rhinoceros (collected in South Africa between 2018 and 2019) and analyzed using the i-STAT. Multiple parameters were higher ( P < 0.05 ) in free ranging versus managed animals including potassium, blood urea nitrogen, creatinine, glucose, hematocrit, and hemoglobin. Conversely, iCa concentrations were higher ( P < 0.05 ) in the managed populations of white rhinoceros. The RI determined for iCa was 1.36–1.56 mmol/L, with a mean of 1.46 mmol/L, and was determined using the guidelines from the American Society for Veterinary Clinical Pathology. There was no difference in anion gap, chlorine, total carbon dioxide, or sodium between the populations. Seasonality and locality of sampling as well as diet may be contributing factors to the higher iCa concentrations in managed rhinoceros. The six elevated parameters in free ranging rhinoceros are likely attributable to dehydration compounded by capture stress. This data provides insight into the state of several biochemical and hematologic parameters in southern white rhinoceros and will allow veterinarians to better assess the health of both managed and free ranging populations.

Background Managed southern white rhinoceros (Ceratotherium simum simum) serve as assurance populations for wild conspecifics threatened by poaching and other anthropocentric effects, though many managed populations experience subfertility and reproductive failure. Gut microbiome and host health are inextricably linked, and reproductive outcomes in managed southern white rhinoceros may be mediated in part by their diet and gut microbial diversity. Thus, understanding microbial dynamics within managed populations may help improve conservation efforts. We characterized the taxonomic composition of the gut microbiome in the managed population of female southern white rhinoceros (n = 8) at the North Carolina Zoo and investigated the effects of seasonality (summer vs. winter) and age classes (juveniles (n = 2; 0–2 years), subadults (n = 2; 3–7 years), and adults (n = 4; >7 years)) on microbial richness and community structure. Collection of a fecal sample was attempted for each individual once per month from July-September 2020 and January-March 2021 resulting in a total of 41 samples analyzed. Microbial DNA was extracted and sequenced using the V3-V4 region of the 16S rRNA bacterial gene. Total operational taxonomic units (OTUs), alpha diversity (species richness, Shannon diversity), and beta diversity (Bray-Curtis dissimilarity, linear discriminant analysis effect size) indices were examined, and differentially enriched taxa were identified. Results There were differences (p < 0.05) in alpha and beta diversity indices across individuals, age groups, and sampling months. Subadult females had higher levels of Shannon diversity (Wilcoxon, p < 0.05) compared to adult females and harbored a community cluster distinct from both juveniles and adults. Samples collected during winter months (January-March 2021) possessed higher species richness and statistically distinct communities compared to summer months (July-September 2020) (PERMANOVA, p < 0.05). Reproductively active (n = 2) and currently nonreproductive adult females (n = 2) harbored differentially enriched taxa, with the gut microbiome of nonreproductive females significantly enriched (p = 0.001) in unclassified members of Mobiluncus, a genus which possesses species associated with poor reproductive outcomes in other animal species when identified in the cervicovaginal microbiome. Conclusion Together, our results increase the understanding of age and season related microbial variation in southern white rhinoceros at the North Carolina Zoo and have identified a potential microbial biomarker for reproductive concern within managed female southern white rhinoceros.

The southern white rhinoceros (Ceratotherium simum simum) faces an uncertain future in the wild due to increased poaching pressure and habitat fragmentation, thus the management of reproductively successful populations is of critical importance.Successful reproductive outcomes in rhinoceros may be mediated by diet and gut microbial diversity; therefore, understanding gut microbial dynamics within and between captive and wild populations may help improve conservation efforts. Accordingly, gut microbiome preservation methods are needed that are practical for in situ field sampling of wild populations. We evaluated the efficacy of 3 different preservation methods over 2 timepoints for stabilizing microbial communities in feces from southern white rhinoceros

Rhinoceros are among the largest and most endangered herbivores in the world. Three of the five extant species are critically endangered, with poaching and habitat loss contributing heavily to declines. The gut microbiome is an essential facet of host health and digestion, mediating a variety of immune and physiological functions. Certain microbes have the potential to serve as biomarkers for reproductive outcomes and predictors of disease susceptibility. Therefore, assessing gut microbial dynamics in relation to wild and managed rhinoceros populations has particular relevance for zoos and other conservation organizations that maintain assurance populations of these charismatic megafauna. The functional gut microbiomes associated with all rhinoceros species remain poorly studied, and many published reports are limited by small sample sizes and sex biases. In this review, we synthesize current research to examine the rhinoceros gut microbiome under human management and resulting conservation implications, address common pitfalls of wildlife gut microbiome studies, and propose future avenues of research in this field.