The research team, led by G. Osthoff of the University of the Free State with collaborators from North-West University and the University of Pretoria, set out with three objectives: to describe quantified blood metabolites in healthy giraffes and southern white rhinoceroses, to test for sex-associated differences within each species, and to compare the two species using matrix-matched samples. The choice of animals was deliberate. Giraffes are foregut-fermenting ruminant browsers, while white rhinoceroses are hindgut-fermenting grazers, meaning their blood chemistry could plausibly differ because of species physiology, diet, and the microbial fermentation that occurs at opposite ends of the digestive tract.

The rhinoceros dataset was substantial: 45 apparently healthy, free-ranging white rhinoceroses, 31 females and 14 males, were sampled during routine management procedures on a single semi-extensive wildlife property in the Northern Cape Province over five days in May 2019. Each animal was immobilised with etorphine, hyaluronidase and azaperone, and blood was drawn from the posterior auricular vein into EDTA tubes, centrifuged within two hours, and stored at minus 80 degrees Celsius. The giraffe data came from 24 valid sampling occasions involving 19 animals at Rooipoort and Sandveld Nature Reserves, with serum collected in 2017 and EDTA plasma from six animals in 2018.

The analytical pipeline was exacting. Samples were filtered through 10 kDa membranes to remove proteins, mixed with a phosphate buffer in deuterium oxide containing an internal standard, and run on a Bruker Avance III HD 500 MHz spectrometer. Metabolites were annotated against pure-compound spectral libraries supplemented with two-dimensional J-resolved and COSY spectra, and identities were graded according to the Metabolomics Standards Initiative, with Level 1 assignments confirmed against reference standards. Concentrations were reported in micromoles per litre, and blank cells where no resonance was discernible were treated as non-detections rather than zeros, a distinction the authors stress is critical for honest interpretation.

The statistics were equally careful. Concentrations were log2-transformed and tested with Welch’s t-test, which does not assume equal variances, followed by Benjamini-Hochberg false-discovery correction across each family of metabolites. Effect sizes were expressed as ratios of geometric means with Hedges’ g confidence intervals, and robustness was probed with equal-variance t-tests, Mann-Whitney U tests, Monte Carlo permutation tests with 50,000 label permutations, and leave-one-out analyses that removed each animal in turn. Notably, the team explicitly declined to use PLS-DA, OPLS-DA, VIP-based feature selection or pathway enrichment as inferential evidence, positioning the study as a model of statistical restraint in a field often criticised for overinterpretation.

The first headline result concerned sex. In the design-compatible giraffe comparison, restricted to 2017 Rooipoort serum from 10 females and six males, no metabolite differed significantly even before correction for multiple testing; the smallest p value, for 3-hydroxyisobutyric acid, was just 0.070. The authors caution that this null result should not be read as proof that the sexes are metabolically equivalent, given the small sample and the absence of a predefined equivalence margin, but it aligns with growing evidence that sex effects are not universal across wildlife metabolomes.

The rhinoceros sex comparison told a more nuanced story. Nine metabolites met the primary false-discovery criterion, with females showing higher N-acetylglucosamine, creatinine, alanine, cholic acid, glycocholic acid, acetoacetic acid, isoleucine and valine, and lower allantoin than males. Yet only N-acetylglucosamine survived every sensitivity analysis, remaining significant under Welch, permutation and rank-based testing and in all 45 leave-one-out runs. Alanine and creatinine showed moderate support, while the remaining six findings were threshold-sensitive, hovering near the significance boundary. The result is a textbook demonstration of why multiplicity control and transparent robustness categories matter: without them, six fragile findings might have been reported alongside one genuinely solid one.

The interspecies comparison produced the study’s most dramatic pattern. Comparing EDTA plasma from six verified 2018 giraffes with all 45 rhinoceroses, 36 of 50 directly comparable metabolites differed significantly, and 28 formed a conservative core supported by every statistical test and every leave-one-giraffe-out analysis. Giraffe plasma contained markedly more pyruvic acid, glycine, allantoin and trimethylamine, and far less methanol, N-acetylglucosamine, acetic acid, 3-hydroxyisovaleric acid and methylamine. Most intriguingly, a coherent pattern emerged among branched-chain amino-acid-related compounds: giraffes showed lower leucine, 2-oxoisocaproic acid, 3-methyl-2-oxovaleric acid, 3-hydroxyisobutyric acid and 3-hydroxyisovaleric acid, consistent with a genuine difference in circulating branched-chain amino-acid chemistry between the species. Lower acetate and propionate in giraffes is biologically compatible with the contrast between foregut and hindgut fermentation, though the study did not measure feed intake or fermentation products directly.

The authors are admirably candid about the limits of their data. Species was perfectly confounded with NMR acquisition batch, since giraffe spectra were acquired in 2018 and rhinoceros spectra in 2021 with no shared quality-control material, so not every difference can be attributed to biology. Collection year was completely confounded with serum versus plasma in the giraffe dataset, precluding any inferential temporal comparison. The six-animal giraffe plasma group, while shown by leave-one-out analysis not to be driven by a single outlier, is small, and the concentrations are offered as exploratory baseline data rather than formal veterinary reference intervals, which would require dedicated reference-interval methodology. Adjustment for sex did not materially change the conservative core, ruling out the different sex ratios as an explanation for the broad pattern.

Why does this matter beyond the curiosity factor? Blood metabolomics is increasingly used in conservation medicine to detect disease, nutritional stress and environmental exposure in endangered species, from iron storage disease in Sumatran rhinoceroses to mitochondrial dysfunction in black rhinoceroses. Reliable baseline data from healthy animals are the foundation on which such diagnostic applications must be built, and they are scarce for wildlife. This study provides carefully curated concentration data for two keystone African herbivores, along with a methodological template, predefined contrasts, multiplicity correction, permutation testing and leave-one-out stability checks, that future wildlife metabolomics studies would do well to follow. The authors call for prospective work sampling both species with the same specimen matrix, balanced sexes, contemporaneous acquisition and shared quality controls. Until then, the branched-chain amino-acid signature separating the world’s tallest ruminant from its second-largest land mammal stands as an intriguing candidate for targeted investigation into how gut architecture writes itself into the blood.

Subject of Research: Comparative 1H-NMR blood metabolite profiling of giraffes and white rhinoceroses

Article Title: Comparative 1H-NMR profiling of plasma and serum metabolites in giraffes and white rhinoceroses

Article References: Osthoff, G., Mason, S., Schmidt, L., Tordiffe, A., & Deacon, F. (2026). Comparative 1H-NMR profiling of plasma and serum metabolites in giraffes and white rhinoceroses. Metabolomics, 22(5), Article 159. https://doi.org/10.1007/s11306-026-02535-0

Image Credits: AI Generated

DOI: 10.1007/s11306-026-02535-0

Keywords: metabolomics, giraffe, white rhinoceros, NMR spectroscopy, blood plasma, serum, branched-chain amino acids, wildlife physiology, conservation medicine, foregut fermentation, hindgut fermentation, South Africa

The pilot study was conducted during the summer of 2023 at two very different UK institutions: the small Fenn Bell Conservation Project in Kent, where 76 visitors observed a pair of Asian small-clawed otters (Aonyx cinereus), and the much larger Twycross Zoo in the Midlands, where 155 visitors studied two Rothschild giraffe (Giraffa camelopardalis rothschildi). Participants were recruited through posters with QR codes at the enclosures and asked to watch the animals for two minutes before completing an online questionnaire built on a pre-defined ethogram, a structured list of species-typical behaviours including positive, negative and neutral welfare indicators. The questionnaire also invited optional sections on how the animals seemed to be feeling, what animal welfare meant to the visitors themselves, and how they had found the citizen science experience.

Technically, the design was deliberately cautious. Because visitor observations could not be paired with simultaneous video observations from the same individual, and because the two data sources differed in duration, the researchers did not treat the comparison as a validation exercise. Instead, they used systematically coded CCTV footage as a reference dataset, applying instantaneous scan sampling with one-minute intervals between 11am and 3pm, and summarising both datasets as hourly and daily presence or absence records. At the daily level, both data sources captured walking or running in the otters on all study days and chewing the cud, eating and drinking, standing and locomotion in the giraffe, while the largest discrepancies appeared for infrequent or harder-to-identify behaviours such as grooming and social interactions.

The psychological results proved equally instructive. Visitors scored the animals on eight qualitative terms, including content, relaxed, agitated, frustrated, comfortable, wary, confident and distressed, and then gave an overall welfare rating from 1 to 10. Spearman’s rank correlations revealed a coherent pattern at both sites: welfare scores rose alongside positively valenced adjectives such as content, comfortable, confident and lively or engaged, and fell alongside negative terms such as frustrated, agitated and wary. For the otters, the correlation with contentment was particularly strong, while for the giraffe even wary and agitated scores tracked downward with welfare ratings. Although participants were told in advance which terms indicated positive or negative welfare, the authors note these exploratory associations provide preliminary evidence of construct validity in public assessments of animal affective states.

Perhaps the most encouraging finding concerned how visitors conceptualised welfare itself. Asked to define or describe animal welfare, most respondents produced answers that mapped cleanly onto the Five Domains model, the contemporary framework covering nutrition, environment, health, behaviour and mental state. At Fenn Bell, 86 percent referenced physiological welfare, 64 percent mental state and 41 percent behaviour; at Twycross the figures were 93, 54 and 24 percent respectively. Fifteen otter visitors and thirteen giraffe visitors touched on all three broad themes, offering definitions such as meeting an animal’s emotional, physical, mental and health needs as naturally as possible through diet, environment and enrichment. The researchers observed, however, that visitors leaned towards input-based measures such as food and space rather than output-based measures such as behaviour, and that behavioural domains were the hardest for the public to articulate.

Where visitors learned their welfare concepts also carried a clear message for the zoo sector. Zoos themselves ranked among the most frequently cited sources of knowledge, with 45 of the Twycross respondents attributing their understanding to that zoo alone, ahead of television documentaries and educational facilities. The authors interpret this as evidence that educational material provided by zoos is being positively received, and they recommend that zoos place greater emphasis on positive behavioural interactions within their welfare science communication. Given that negative public perceptions of welfare can erode trust in zoos and reduce willingness to engage in conservation efforts, effective communication of welfare science is not a luxury but a strategic necessity for modern institutions.

Engagement levels were striking. At Twycross, where a researcher was present at the enclosure to encourage participation, an average of 27 visitors per day completed the survey; at the smaller Fenn Bell site, where participation was self-directed, the mean was 3.4 per day. Across both sites, 93 to 95 percent of respondents said they would take part in a similar activity again, and 79 percent overall described the process as rewarding. Crucially, the majority of participants were infrequent zoo visitors, with the largest group attending less than once a year, suggesting that citizen science could reach beyond the committed membership base of season-pass holders. Most participants also expressed confidence in their ability to identify the behaviours on the ethogram, which the researchers attribute to the deliberately simple design of the observation task.

The study is candid about the limitations of visitor-generated behavioural data. The otters were out of sight of the cameras for 67 percent of video observations, and both visitors and cameras faced blind spots and varying viewing opportunities. Behaviours that were infrequent or complex, such as positive social interactions in the otters or grooming in the giraffe, showed the greatest divergence between the two datasets. The authors stress that their analyses are exploratory descriptions of behavioural occurrence rather than measures of observer accuracy or reliability, and they call for future studies using time-matched designs, cameras positioned to replicate the visitor’s view, and controlled comparisons with trained observers to enable formal inter-rater reliability assessment. Training, structured prompts and simplified measures such as active versus inactive states are proposed as ways to improve data quality.

Beyond the data, the researchers argue, the process itself may deliver benefits that matter to the mission of the modern zoo. Watching animals closely is known to foster empathy and a sense of connectedness, visiting zoos has been linked to improved human wellbeing, and citizen science participation has been associated with gains in scientific understanding. Longer dwell times at exhibits may not automatically translate into learning, but they can deepen the visitor experience and support lasting connections with nature. As biodiversity losses reach unprecedented levels and conservation science becomes an ever more urgent discipline, the authors conclude that engaging zoo visitors in behavioural citizen science deserves far wider consideration, both as a source of data on how animals spend their opening hours and as a pathway to a more empathetic, conservation-minded public.

The study sits within a broader rethinking of what zoos are for. Traditional frameworks described zoos through four pillars of conservation, education, research and recreation, but more recent models have proposed adding a fifth pillar of wellbeing that applies to both animals and people, alongside a ‘sphere of influence’ recognising that zoos operate at local, national and global scales. Within that framing, communicating welfare science to the public is not peripheral but central, since public trust depends heavily on whether visitors believe the animals they are watching are thriving.

Citizen science itself is usually understood as having two distinct strands. In one, the priority is collecting usable data at scale, as in large wildlife monitoring programmes; in the other, the priority is engaging citizens, with data quality a secondary concern. The zoo project deliberately straddled both, and the tension between them explains much of the authors’ caution about the behavioural records. Previous zoo-based citizen science in the UK, such as campaigns encouraging visitors to log native species seen on site, has built ecological awareness but stopped short of fostering connections with the zoo’s own animals, a gap this study sought to address.

The choice of study species was pragmatic rather than incidental. Asian small-clawed otters and Rothschild giraffe were selected because they were consistently visible from public viewing areas, attracted longer dwell times, and could accommodate camera installations allowing simultaneous remote observation. Behavioural research is already the dominant form of zoo science, valued for capturing real-time information about animal experiences at low cost, yet large-scale data collection can be impractical for busy animal care staff. Distributing observation across millions of annual visitors offers one possible solution, provided questions of validity and reliability are resolved.

Earlier work also suggests the timing matters: visitors report more positive experiences and stronger feelings of connection after watching animals, particularly active ones, meaning the observation task itself may amplify the very engagement the projects aim to cultivate.

Subject of Research: Citizen science engagement of zoo visitors in animal behaviour and welfare assessment

Article Title: Exploring citizen science as a tool for engaging zoo visitors with animal welfare

Article References: Stephens, D., Wright, D., Rowden, L., Frost, N., Carter, A., Ward, S. J., & Williams, E. (2026). Exploring citizen science as a tool for engaging zoo visitors with animal welfare. Discover Animals, 3(1), Article 85. https://doi.org/10.1007/s44338-026-00247-2

Image Credits: AI Generated

DOI: 10.1007/s44338-026-00247-2

Keywords: citizen science, zoos, animal welfare, animal behaviour, Five Domains model, ethogram, visitor engagement, giraffe, Asian small-clawed otter, conservation education, public engagement, affective state