Marcus Clauss

University of Zurich | UZH · Clinic of Zoo Animals, Exotic Pets and Wildlife

Currently the only captive population of beira antelope (Dorcatragus megalotis) is held at the Al Wabra Wildlife Preservation, Qatar. An outbreak of a severe respiratory disease--fibrinous pleuropneumonia syndrome, most likely caused by Mycoplasma ovipneumoniae--led to a marked population decline. Reactive systemic inflammatory (AA) amyloidosis was...

Studies of diurnal primates have long considered the nocturnal period to be a time spent merely sleeping and not effectively utilized for foraging or social behaviours. However, digestive activity should continue during the night. To explore the adaptive significance of the primate rumination‐like behaviour, that is, regurgitation and re‐masticatio...

(no abstract)

The naturally occurring stable isotopes of potassium (41K/39K, expressed as δ41K) have the potential to make significant contributions to vertebrate and human biology. The utility of K stable isotopes is however conditioned by the understanding of the dietary and biological factors controlling natural variability of δ41K. This paper reports a syste...

Both teeth and the digestive tract show adaptations that are commonly interpreted in the context of trophic guilds—faunivory, herbivory and omnivory. Teeth prepare food for the digestive tract, and dental evolution focuses on increasing durability and functionality; in particular, size reduction of plant particles is an important preparation for mi...

Among mammals, hippopotamids (‘hippos’) have been described as the species with the lowest chewing efficacy despite elaborate enamel folds on the occlusal surface or their cheek teeth, which was hypothesized to result from the lack of a grinding chewing motion. We investigated the chewing and dentition of the two extant hippo species, the common hi...

Although all hystricomorph rodents have the colonic furrow or groove that is the anatomical prerequisite for a ‘mucous trap’ colonic separation mechanism linked to coprophagy or cecotrophy, the taxon that gives this group its name, the porcupines, have been claimed to not practice coprophagy. Absence of coprophagy has repeatedly been claimed for hy...

Hindgut fermenting herbivores from different vertebrate taxa, including tortoises, and among mammals some afrotheria, perissodactyla incl. equids, several rodents as well as lagomorphs absorb more calcium (Ca) from the digesta than they require, and excrete the surplus via urine. Both proximate and ultimate causes are elusive. It was suggested that...

As part of a comparative research agenda that promises insights that help extend the human lifespan and combat cancer, cancer prevalence in zoo animals has received recent attention. Here, we want to draw attention to a principle of cancer research that was introduced into the zoo world as early on as 1933, but that seems to have gone somewhat forg...

In nutrient-poor wildlife reserves it has become common-practice to provide supplemental mineral resources for wildlife. Yet, the impacts of anthropogenic mineral supplementation on large herbivore nutrition, behaviour, and subsequent impact on ecosystem processes have received little attention. Here, we examine the contribution of anthropogenic mi...

Ruminants differ in the pattern how small particles and liquids pass through their gastrointestinal tract, and in particular their reticulorumen (RR). Based on that they may be classified into 'moose-type' and 'cattle-type' species (smaller and larger differences between particle and liquid passage, respectively). The ratio between the retention of...

Synopsis Hard tissue formation patterns and rates reveal details of animal physiology, life history, and environment, but are understudied in reptiles. Here, we use fluorescence labels delivered in vivo and laser confocal scanning microscopy to study tooth and bone formation in a managed group of green iguanas (Iguana iguana, Linné 1758) kept for 1...

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...

The drivers of dental wear and compensatory hypselodont tooth growth are of current research interest. Expanding previous macroscopic dental wear measurements based on microtomographic scans of guinea pigs ( Cavia porcellus ) fed natural diets, we added diet groups with different predicted drivers of dental wear and analysed how measured variables...

Sodium (Na) plays a critical role in the functioning of terrestrial ecosystems. In Na-poor regions, plant consumers may experience Na deficiency and adapt by seeking supplementary Na resources. This can markedly impact animal behavior, space-use, and co-existence, with concomitant impacts on ecosystems. Many studies have noted that Na-seeking behav...

The dietary nutrient profile has metabolic significance and possibly contributes to species' foraging behavior. The brown bear (Ursus arctos) was used as a model species for which dietary ingredient and nutrient concentrations as well as nutrient ratios were determined annually, seasonally and per reproductive class. Brown bears had a vertebrate- a...

Sheep with a relatively low methane yield were observed to have shorter fluid and particle mean retention times (MRT). Because the application of pilocarpine, a saliva stimulant, was successful in reducing retention times in ruminants in previous studies, we applied this substance to sheep, expecting a reduction in MRT and methane yield. Three non-...

Like other members of the even-toed ungulates (the perissodactyls), equids once had a higher species diversity in the fossil record than they have today. This is generally explained in comparison to the enormous diversity of bovid ruminants. Theories on putative competitive disadvantages of equids include the use of a single toe as opposed to two t...

High fluid turnover in the rumen has been shown beforewas indicated to elevate the harvest of microbial yield from the forestomach. Microbial synthesis consumes metabolic hydrogen, competing with methanogenesis. Accordingly, iIn animals as well as in vitro continuous culture systems, high fluid turnover was linked to decreased methane yield [1, 2]....

The evolution of mammals is characterized, amongst other developments, by an increasing relevance of effective food processing in form of an increasingly durable dentition, complex occlusal surfaces, and transverse chewing movements. Some factors have received increasing attention for the facilitation of the latter, such as the configuration of the...

Ruminant species differ in digestive physiology. The species-specific ratio of mean retention time of particles and fluid (MRTparticle/MRTfluid) in the reticulorumen has been interpreted as controlling ruminal fermentation: a higher ratio indicates of a more distinct 'washing' of particulate digesta by liquid. This should increase the harvest of mi...

Traditional husbandry practices for the public display of Callitrichidae involve strict separation of animals and public. An important consideration for the evaluation of such management is the occurrence of health problems and potential zoonotic risks. This study compared animal data and veterinary records from a captive, free-roaming population o...

Fecal consistency is routinely used as an indicator of gastrointestinal health and diet suitability in zoo animals. The underlying processes in ungulate fecal consistency are not often investigated. The authors assessed multiple factors on fecal consistency scores in six adult zoo moose (Alces alces) retrospectively for a 3-yr period. All animals w...

Dental wear due to ingestion of dust and grit has deleterious consequences. Herbivores that could not wash their food hence had to evolve particularly durable teeth, in parallel to the evolution of dental chewing surface complexity to increase chewing efficacy. The rumen sorting mechanism increases chewing efficacy beyond that reached by any other...

In mammals, complex dental microwear textures (DMT) representing differently sized and shaped enamel lesions overlaying each other have traditionally been associated with the seeds and kernels in frugivorous diets, as well as with sclerotized insect cuticles. Recently, this notion has been challenged by field observations as well as in vitro experi...

In nutrient-poor wildlife reserves it has become common-place to provide supplemental mineral resources for wildlife. Yet, the impacts of anthropogenic mineral supplementation on community-wide wildlife nutrition, behaviour and subsequent impact on ecosystem processes remain poorly understood. Here, we examine the contribution of anthropogenic mine...

Both in vitro and animal studies indicated that a higher dilution rate is related to a more efficient microbial synthesis and a lower methane (CH4) yield. The latter could be a consequence of the former, as an increase in microbial cell synthesis offers an alternative hydrogen sink competing with methanogenesis. To test this assumption in live anim...

In the discussion about zoo elephant husbandry, the report of Clubb et al. (2008, Science 322: 1649) that zoo elephants had a "compromised survivorship" compared to certain non-zoo populations is a grave argument, and was possibly one of the triggers of a large variety of investigations into zoo elephant welfare, and changes in zoo elephant managem...

Introduction: The grinding intensity of pig feed is considered one potential predisposing factor for gastric ulcers, and a variety of particle size recommendations have been published for pig feeds. We subjected 51 different commercial compound feeds for pigs (38 meals, 13 pellets/granulates) to dry and/or wet sieve analysis. The amount of particl...

Dental microwear texture (DMT) analysis is used to differentiate abrasive dental wear patterns in many species fed different diets. Because DMT parameters all describe the same surface, they are expected to correlate with each other distinctively. Here, we explore the data range of, and correlations between, DMT parameters to increase the understan...

Muroid rodents mostly have a complex stomach: one part is lined with a cornified (non‐glandular) epithelium, referred to as a 'forestomach,' whereas the rest is lined with glandular epithelium. Numerous functions for the forestomach have been proposed. We collated a catalog of anatomical depictions of the stomach of 174 muroid species from which th...

Sieve analyses of hindgut contents of horses as well as observations in horses where plastic markers had been applied to a caecal cannula suggested that there may be a discrimination by particle size in the passage or retention of digesta. Here, we performed a similar experiment with five caecum‐cannulated horses (562 ± 31 kg) fed a constant amount...

A link between diet and avian intestinal anatomy is generally assumed. We collated the length of intestinal sections and body mass of 390 bird species and tested relationships with diet, climate and locomotion. There was a strong phylogenetic signal in all datasets. The total and small intestine scaled more-than-geometrically (95%CI of the scaling...

While information on individual differences in digesta mean retention time (MRT) might be interesting when selecting phenotypes for digestive efficiency, MRT measurements are prohibitively labour‐intensive for large‐scale application. Therefore, more easily measured proxies of MRT might be helpful. We used the opportunity of an experiment applying...

The aim of this study was to determine the effect of an increased mono‐ and disaccharide (MD) intake on selected functions and structure of the gastrointestinal tract (GIT), and selected blood parameters in Reeves's muntjac (Muntiacus reevesi), a small browsing ruminant. Eighteen male muntjacs were fed diets consisting of lucerne (ad libitum), a hi...

Introduction: The development of gastric ulcers in pigs has various reasons. In Switzerland, the last survey on the prevalence of gastric ulcers and possible risk factors was performed in 2005. We aimed to reassess gastric ulcers prevalence today, in 2021. A total of 1005 stomachs from fattening pigs from 136 batches and around 87 herds were evalu...

Objectives: Colobines are a group of foregut-fermenting AfroEurasian monkeys that includes more than 70 species grouped into 10 genera which are widely distributed throughout Asia and Africa. Colobines are classified as tripartite or quadripartite based on the number of compartments in their stomach. To expand our understanding of their morphophysi...

Despite increased research during the past years, many characteristics of resting behavior in elephants are still unknown. For example, there is only limited data suggesting elephants express longer lying bouts and increased total nightly lying durations on soft substrates as compared to hard surfaces. Additionally, it has not been investigated how...

Hypselodont (ever-growing) teeth of lagomorphs or rodents have higher wear rates (of a magnitude of mm/week), with compensating growth rates, compared to the non-ever-growing teeth of ungulates (with a magnitude of mm/year). Whether this is due to a fundamental difference in enamel hardness has not been investigated so far. We prepared enamel sampl...

Free-ranging animals make dietary choices that affect their nutritional status and, ultimately, their health and fitness. We investigated food selection by a leaf-eating foregut-fermenting primate, the guereza (Colobus guereza), using multiple criteria, including chemical and mechanical properties, in vitro digestibility and leaf abundance, on the...

There are different descriptions of allometric relationships between important components of the mammalian skull. Craniofacial evolutionary allometry describes a pattern of increasing facial cranium in larger skulls. Another body of literature describes disproportionately larger teeth in smaller species or specimens, matching anecdotal observations...

The Colobines are a group of Afroeurasian monkeys that exhibit extraordinary behavioural and ecological diversity. With long tails and diverse colourations, they are medium-sized primates, mostly arboreal, that are found in many different habitats, from rain forests and mountain forests to mangroves and savannah. Over the last two decades, our unde...

Prominent ontogenetic changes of the gastrointestinal tract (GIT) should occur in mammals whose neonatal diet of milk differs from that of adults, and especially in herbivores (as vegetation is particularly distinct from milk), and even more so in foregut fermenters, whose forestomach only becomes functionally relevant with vegetation intake. Due t...

On the one hand, the greater kudu (Tragelaphus strepsiceros) is a strict browser and would therefore be expected to display a ‘moose-type’ digestive physiology with a comparatively low rumen fluid throughput, a low ratio of small particle to fluid mean retention time (MRT) in the reticulorumen (RR), and relatively unstratified RR contents. On the o...

Rationale: Blood water oxygen isotope compositions can provide valuable insights into physiological processes and ecological patterns. While blood samples are commonly drawn for medical or scientific purposes, blood fractions are infrequently measured for oxygen isotopic compositions (δ18 O) because such measurements are time consuming and expensi...

Mammals whose breeding activity is triggered by seasonal photoperiodic cues typically maintain seasonal reproduction in zoos, with births accumulating to various degrees in spring. For zoo-kept rhinoceroses, accumulation of births in autumn has been suggested, which would make this group unusual. We compare birthing (and hence conception) patterns...

In der Schweiz bringen Tierparks den Menschen die einheimische Fauna in ihren Lebens- und Verhaltensweisen in teils extensiven, modernen Tierhaltungs-Konzepten näher. Dabei ist die Darstellung des Miteinanders von Mensch-, Haus- und Wildtier ein Schwerpunkt, dessen Wichtigkeit zum Beispiel aufgrund aktueller Diskussionen um das Umgehen mit anwachse...

Bei der Haltung von (Wild)Tieren nimmt man Abweichungen von den Bedingungen in Kauf, die diese in ihrem natürlichen Habitat vorfinden. Je nach dem Zweck der Haltung und ihrer damit verbundenen Dauer mögen solche Abweichungen mehr oder weniger zu rechtfertigen sein. Hinsichtlich der Futterzusammensetzung, solche Abweichungen sind schon lange bekannt...

Elephant endotheliotropic herpesvirus-haemorrhagic disease (EEHV-HD) is the most common cause of death in juvenile captive Asian elephants Elephas maximus. Currently, weekly whole blood screening is recommended for the detection of viraemia, which occurs prior to the development of clinical disease, but there are no recommendations for monitoring v...

While there is ample concern about the welfare of animals kept in zoos, the fact that living in natural habitats exposes animals to constant threats is rarely emphasized. On the contrary, the fact that zoos—advocates of animal welfare— promote conservation, often without stating an explicit reason, gives rise to the notion that “the wild” is the op...

External quartz abrasives are one of the driving forces of macrowear in herbivorous animals. We tested to what extent different sizes and concentrations influence their effect on tooth wear. We fed seven pelleted diets varying only in quartz concentration (0%, 4%, and 8%) and size (fine silt: ∼4 μm, coarse silt: ∼50 μm, fine sand: ∼130 μm) to rabbi...

Comparisons of wild and domestic populations have established brain reduction as one of the most consistent patterns correlated with domestication. Over a century of scholarly work has been devoted to this subject, and yet, new data continue to foster its debate. Current arguments, both for and against the validity of brain reduction occurring in d...

In investigations of differences between ruminant species feeding on browse or grass, it is often unclear whether observed differences are animal- or forage-specific. Ruminant species have been classified as ‘moose-type’, with little rumen content stratification, or ‘cattle-type’ with a distinct rumen contents stratification, including a gas layer....

The coexistence of multiple species competing for a finite set of resources is a widely debated topic in community ecology. Species with strongly overlapping niches are expected to drive each other towards exclusion, but such species may also coexist if they have similar competitive abilities. This compromise can lead to a peculiar pattern of clump...

We determined location and amount of accumulated sand in the gastrointestinal tract (GIT) of rabbits (Oryctolagus cuniculus) and guinea pigs (Cavia porcellus) fed diets containing external (silicate) abrasives. Computed tomographic abdominal images of rabbits (n=44) and guinea pigs (n=16) that each received varying numbers (4-7) of different diets...

Colobine monkeys are known for the anatomical complexity of their stomachs, making them distinct within the primate order. Amongst foregut fermenters, they appear peculiar because of the occurrence of two different stomach types, having either three (‘tripartite’) or four (‘quadripartite’, adding the praesaccus) chambers. The functional differences...

This study investigated the impact of carbohydrate source and fluid passage rate (dilution rate) on ruminal fermentation characteristics and microbial crude protein ( MCP ) formation. Three commonly used feeds (barley grain [ BG ], beet pulp [ BP ], and soybean hulls [ SBH ]), which differ considerably in their carbohydrate composition, were incuba...

Diel activity patterns of animal species reflect constraints imposed by morphological, physiological, and behavioral trade-offs, but these trade-offs are rarely quantified for multispecies assemblages. Based on a systematic year-long camera-trap study in the species-rich mammal assemblage of Lake Manyara National Park (Tanzania), we estimated activ...

Bamboo is an enigmatic forage, representing a niche food for pandas and bamboo lemurs. Bamboo might not represent a suitable forage for herbivores relying on fermentative digestion, potentially due to its low fermentability. To test this hypothesis, guinea pigs (n = 36) were used as model species and fed ad libitum with one of three forages (bamboo...

The outfit of husbandry facilities of, and the enrichment provided for, experimental rodents plays an important role in the animals’ welfare, and hence also for the societal acceptance of animal experiments. Whether rats and mice benefit from being provided with running wheels or plates is discussed controversially. Here we present observations fro...

Dietary reconstruction in vertebrates often relies on dental wear-based proxies. Although these proxies are widely applied, the contributions of physical and mechanical processes leading to meso-and microwear are still unclear. We tested their correlation using sheep (Ovis aries, n = 39) fed diets of varying abrasiveness for 17 months as a model. V...

In paleontology and biology, measures that correlate with specific traits are often used as proxies for these traits without a clear concept of how their discriminatory power is assessed. This note warns about this practice.

Although relationships between intestinal morphology between trophic groups in reptiles are widely assumed and represent a cornerstone of ecomorphological narratives, few comparative approaches actually tested this hypothesis on a larger scale. We collected data on lengths of intestinal sections of 205 reptile species for which either body mass (BM...

Zoos need to evaluate their aim of high husbandry standards. One way of approaching this is to use the demographic data that has been collected by participating zoos for decades, assessing historical change over time to identify the presence or absence of progress. Using the example of carnivores, with data covering seven decades (1950–2019), 13 ca...

In ruminants, the level of food intake affects net chewing efficiency and hence faecal particle size. For nonruminants, corresponding data are lacking. Here, we report the effect of an increased food intake of a mixed diet in four domestic rabbit does due to lactation, and assess changes in particle size (as determined by wet sieving analysis) alon...

Dust and grit are ingested by herbivores in their natural habitats along with the plants that represent their selected diet. Among the functions of the rumen, a washing of ingesta from adhering dust and grit has recently been demonstrated. The putative consequence is a less strenuous wear on ruminant teeth by external abrasives during rumination. T...

Dental microwear texture analysis (DMTA) is widely used for diet inferences in extant and extinct vertebrates. Often, a reference tooth position is analysed in extant specimens, while isolated teeth are lumped together in fossil datasets. It is therefore important to test whether DMT is tooth position specific, and if so, what the causes for wear d...

Cattle are one of the most intensively bred domestic animals, providing humans with a multitude of products and uses. Using data from the fossil record, we test if their domestication, as for other taxa, has resulted in a reduction of their brain size. We not only conclude that Bos taurus (domestic cattle) have smaller brains than their wild ancest...

Breath and diet samples were collected from 29 taxa of animals at the Zurich and Basel Zoos to characterize the carbon isotope enrichment between breath and diet. Diet samples were measured for δ ¹³ C and breath samples for CH 4 /CO 2 ratios and for the respired component of δ ¹³ C using the Keeling plot approach. Different digestive physiologies i...

Among the different factors thought to affect dental wear, dietary consistency is possibly the least investigated. To understand tooth wear of herbivorous animals consuming different dietary consistencies with different abrasive potential, we fed 14 rabbits (Oryctolagus cuniculus) exclusively with a timothy grassmeal‐based diet in either pelleted o...

p>High 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 nine in situ populations of 0.01–0.7 individuals per km² density range on...

On the one hand, oral processing - mastication - is considered a relatively inflexible component of mammalian feed acquisition that constrains instantaneous intake rates. On the other hand, experimental data shows that the level of feed intake affects faecal particle size and hence net chewing efficiency in ruminants, with larger particles occurrin...

Animals concentrate key nutrients in their bodies. In fenced wildlife reserves where nutrient input and/or retention is low, the off‐site removal of animals may constitute a significant loss of nutrients for the ecosystem. Here we add wildlife capture and removal into the phosphorus (P) and calcium (Ca) budget for a 121,700 ha fenced game reserve l...

It is generally accepted that microbial digestion contributes little to digesta particle size reduction in herbivores, and that faecal particle size reflects mainly chewing efficiency, and may vary with diet. Nevertheless, a decrease in mean particle size (MPS) along the gastrointestinal tract (GIT) has been reported, especially in hindgut fermente...

Colobine monkeys are known for the anatomical complexity of their stomachs, making them distinct within the primate order. Amongst foregut fermenters, they appear peculiar because of the occurrence of two different stomach types, having either three (‘tripartite’) or four (‘quadripartite’, adding the praesaccus) chambers. The functional differences...

Rumen content stratification and the degree of dissociation of particle and fluid retention in the reticulorumen differ between ‘moose-type’ and ‘cattle-type’ ruminant species. These differences are not strictly linked to diet, except for a seeming limitation of ‘moose-type’ ruminants to a browsing niche. Nevertheless, these differences can be plau...

Grading the fecal consistency of carnivores is a frequently used tool for monitoring gut health and overall digestion. Several fecal consistency grading systems are available for mainly felids and canids. No such system exists for the brown bear (Ursus arctos Linnaeus, 1758). We aim at extending current fecal consistency grading systems with a scor...

An often-stated ecomorphological assumption that has the status of ‘textbook knowledge’ is that the dimensions of the digestive tract correlate with diet, where herbivores—consuming diets of lower digestibility—have longer intestinal tracts than faunivores—consuming diets of higher digestibility. However, statistical approaches have so far failed t...

Zoological gardens are considered important institutions for human-animal interactions. Facilitating human-animal contacts and the simultaneous protection of the animals from possible distress by visitors represent an important task of zoological gardens. We investigated the effects of a new roughage feeding setup for zoo-kept domestic herbivores o...

Historically, giraffes (Giraffa spp.) in zoos are known to have a high prevalence of deaths associated with serous fat atrophy, which has been linked to the impression that as browsers, they are more difficult to feed appropriately compared to grazing ruminants. Therefore, one could expect zoohoused giraffes to be peculiar in that they might have,...