Under conditions of dietary sodium (Na+) excess, the kidneys may fail to adequately excrete Na+, potentially compromising blood pressure homeostasis. Body tissues, such as skin, can offer sites of short-term extrarenal Na+ storage and previous research has shown that this can help guard against hypertension in small mammals (e.g., rodents). Large mammals have relatively greater Na+ storage potential, but whether extrarenal Na+ storage occurs for this group is unknown. Here, we report preliminary evidence of extrarenal Na+ storage in cattle. We provided a large pulse-dose of NaCl to four cattle (body mass: 720 kg) and measured excretion of Na+ and potassium (K+) in urine and faeces for a period of 7-days. Following NaCl administration, Na+ excretion spiked in both urine and faeces for 48 h before returning to baseline measurements. After 96 h, however, Na+ excretion increased again; a consistent physiological phenomenon across all individuals studied. We did not observe a pattern in urinary K+ excretion, indicating that the mechanism of Na+ storage does not appear to involve exchange for K+. However, faecal K+ excretion was reciprocal to that of Na+, presumably reflecting exchange of Na+/K+ across the walls of the large intestine. We infer that during the initial period of Na+ stress, short-term extrarenal Na+ storage occurred and the stored Na+ was later released only when the body had returned to Na+ homeostasis. Additional experiments are required to understand how patterns of Na+ regulation changes across body sizes and the specific body compartments involved. Cattle may be a useful model system for examining the impact of high Na+ intake in mammals larger than humans.

The assimilation, retention, and release of nutrients by animals fundamentally shapes their physiology and contributions to ecological processes (e.g., zoogeochemistry). Yet, information on the transit of nutrients through the bodies of large mammals remains scarce. Here, we examined how sodium (Na), a key element for animal health and ecosystem functioning, travels differently through fecal and urinary systems of cows (Bos taurus) and horses (Equus ferus caballus). We provided a large dose of Na and compared its timing of release in feces and urine to that of nonabsorbable markers. Na excretion by urine occurred approximately twice as fast as excretion by feces, yet both were shorter than indigestible particle markers. These differences correspond to rapid absorption of Na in the upper gastrointestinal tract and transport by blood to the kidneys (urine Na excretion) or resecretion of Na into the lower intestinal tract (fecal Na excretion). Interestingly, for cows, we found a second peak of Na excretion in urine and feces > 96 h after dosage. This result may indicate that surplus Na can be rapidly absorbed and stored in specific body cells (e.g., skin), from which it is later released. Using a propagule dispersal model, we found that the distance of cattle- and horse-driven nutrient dispersal by urine was 31% and 36% less than the fecal pathway and 60% and 41% less than the particle marker pathway, which is commonly used to estimate nutrient dispersal. Future physiological and zoogeochemical studies should resolve different pathways of nutrient retention and release from large mammals.

White rhinos (WR, Ceratotherium simum) are grazers and black rhinos (BR, Diceros bicornis) are browsers; this difference has been related to BR being more challenging in terms of husbandry. Previous reports indicated that BR in zoos often receive diets with a higher proportion of easily digestible compounds compared to other rhino species. Additionally, BR are susceptible to iron overload disorder (IOD). We compared the feeding methods and recommendations, and sampled diets and feces of 117 WR and 82 BR across 41 European zoos. The few available data for free-ranging animals were also incorporated. The percentage of forage in the total estimated dry matter intake was 93% for WR and 77% for BR, matching fecal parameters indicating a higher diet digestibility in BR. BR received higher levels of (pelleted) compound feeds and produce than WR. Nevertheless, dietary fiber levels were similar to that reported for free-ranging specimens in both species. Zoo diets were higher in several minerals (Na, P, Cu, Zn) than natural diets. However, zoo BR received diets with similar iron content to that described in free-ranging BR diet items and fecal iron levels were not higher than those in the few samples of free-ranging BR available, suggesting that iron levels in zoo BR diets are not overly excessive. Consequently, IOD appears to be more complex, associated with iron bioavailability and possibly non-dietary causes. Grass hay was used in 100% of WR and 36% of BR (all BR facilities used lucerne hay). BR feces had levels of abrasive silica comparable to those of free-ranging WR and much higher than free-ranging BR, matching reports of excessive tooth wear in adult BR. Browse provision for BR could not be quantified but appeared low in general; no alternative forages (like sainfoin) were fed. Efforts to consistently provide high amounts of browse to BR must be increased and forage should be low in iron and abrasive silica.

Nutritional ecology is vital to understanding food selection in chimpanzees (Pan troglodytes). However, there are knowledge gaps for chimpanzees in savanna landscapes concerning the nutrients of their foods as well as their daily energy and macronutrient intakes. The aims of this study are to (1) examine how adult male chimpanzees in a semiarid savanna select their foods and (2) compare chimpanzee foods between the savanna and forest. We conducted full-day focal follows to observe food processing behavior (87 days) and comprehensively measure daily food intake (25 days). We sampled 49 plant and four insect species to estimate their energy and macronutrient contents. Food consumption correlated positively with its profitability (caloric yield per hour) but was not associated with food abundance or distribution. Daily intakes of metabolizable energy and of water-soluble sugars were higher in the baobab (Adansonia digitata) season than in the non-baobab season and social rank boosted sugar intakes, suggesting that high-sugar foods are prized by Fongoli chimpanzees. In support of the idea that a scarcity of ripe fleshy fruits is an environmental pressure at Fongoli, chimpanzees commonly ingested unripe fruit and seeds, mostly of nonfleshy types, potentially for their protein content or as moderate sources of sugar, fat, and water. Our study indicates that the savanna is not a low-protein habitat and suggests ways that chimpanzees-and potentially early hominins-have adapted to meet daily nutritional requirements in a savanna environment.

The European roe deer (Capreolus capreolus) is unique among artiodactyls for undergoing embryonic diapause, a 4-5 months period of reduced embryonic development at the blastocyst stage. However, our knowledge of the reproductive physiology and endocrinology of the seasonal roe deer, particularly regarding embryo development and diapause, remains limited. Addressing this knowledge gap is crucial and necessitates further advancements in reproductive technologies. Here, this case report documents the first successful artificial insemination resulting in a pregnancy and live birth in this species, marking a significant breakthrough in its reproductive management. The timing of artificial insemination was assessed through careful behavioral observations of the time of mating by a vasectomized teaser buck. Cervical insemination was then performed using frozen-thawed sperm collected earlier from a fertile buck. DNA sequencing of the progeny, the parents and non-related individuals in the herd confirmed the parent-offspring relationship between the fawn and the sperm donor buck. While this study serves as a proof of concept, it also identifies potential areas for enhancement, such as improving estrus detection methods, sperm handling techniques, and the insemination procedure itself. This research paves the way for advanced reproductive strategies in roe deer and potentially other species with similar reproductive characteristics.

The aim of the study was to determine long-term effects of a hay- or concentrate-based diet in sheep. Twenty-four lambs (12 male/12 female; 7-14 days of age) were randomly divided into two groups, i.e. control (C) and high-starch (HS), and kept in four group pens (2 pens/treatment). HS group were fed ad libitum concentrate mixture, while C group meadow hay with up to 150 g/day/animal of concentrate mixture. Both treatments were fed milk replacer (MR) for 6 weeks and experimental solid feeds for 4 additional weeks after weaning (stage 1). From week 11 onwards, both groups were transitioned to a forage-based diet and continued for 5 months (males) and 7 months (females; stage 2). Thereafter, animals were placed in individual pens for measuring voluntary dry matter (DM) intake, digesta retention, and DM digestibility (stage 3), and subsequently challenged with a high-starch diet (stage 4). Body weight (BW) did not differ between treatments (P = 0.16) but was numerically greater for HS group during the weaning transition (group x time interaction; P < 0.01). Plasma glucose was higher for HS in month 1 and 2, plasma cholesterol and serum non-esterified fatty acids (NEFA) lower for HS in month 2, and serum NEFA was higher for HS in month 4 of the study (group x time interaction; P < 0.01). Furthermore, plasma glucose and cholesterol and serum NEFA were lower for HS in month 6 of the study (group x time interaction; P < 0.01). In stage 1, C spent more time eating solid feed and ruminating, and HS walking, standing, licking salt lick and performing abnormal behaviors (P < 0.01). In stage 2, C spent more time standing and HS walking, ruminating and licking salt lick (P <= 0.03). DM intake and BW did not differ between treatments in stage 3 (P >= 0.35). Fluid and small particle retention time in the reticulorumen of ewes tended to (P <= 0.10) and large was longer for C (P = 0.04). In stage 4, rumen pH of males was lower for HS (P = 0.01). Whereas feeding a high-starch diet early in life had no long-term effects on DM intake or BW, it did have long-term impacts on blood parameters, selected behaviors, rumination, and digesta retention. Furthermore, the diet provided early in life influenced the ruminal response to a high-starch diet later in life. However, not all observed differences between C and HS were consistent between ewes and rams.

Pathogens often occur at different prevalence along environmental gradients. This is of particular importance for gradients of anthropogenic impact such as rural-urban transitions presenting a changing interface between humans and wildlife. The assembly of parasite communities is affected by both the external environmental conditions and individual host characteristics. Hosts with low body weight (smaller individuals or animals with poor body condition) might be more susceptible to infection. Furthermore, parasites' mode of transmission might affect their occurrence: rural environments with better availability of intermediate hosts might favour trophic transmission, while urban environments, typically with dense definitive host populations, might favour direct transmission. We here study helminth communities (141 intestinal samples) within the red fox (Vulpes vulpes), a synanthropic host, using DNA metabarcoding of multiple marker genes. We analysed the effect of urbanisation, seasonality and host-intrinsic (weight, sex) variables on helminth communities. Helminth species richness increased in foxes with lower body weight and in winter and spring. Season and urbanisation, however, had strong effects on the community composition, i.e., on the identity of the detected species. Surprisingly, transmission in two-host life cycles (trophic transmission) was more pronounced in urban Berlin than in rural Brandenburg. This disagrees with the prevailing hypothesis that trophically transmitted helminths are less prevalent in urban areas than in rural areas. Generally, co-infestations with multiple helminths and high infection intensity are associated with lighter (younger, smaller or low body condition) animals. Both host-intrinsic traits and environmental drivers together shape parasite community composition and turnover along urban-rural gradients.

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 particles and fluids is called the 'selectivity factor' (SF) and is a species-specific characteristic, studied in tragulids, giraffids and bovids, but not in many cervid species. Recently, it has been suggested that a high SF might also serve to wash digesta clean of external abrasives prior to regurgitation for rumination. In this study, we measured SF and passage kinetics (using a liquid marker and markers of different particle size, fed with the diet) in a capreoline deer, the southern pudu (Pudu puda, n = 5, 10.3 ± 2.9 kg, kept at two zoos) and a cervine deer, the Reeves's muntjac (Muntiacus reevesi, n = 6, 11.0 ± 1.7 kg, kept at a research facility). The relative daily dry matter intake (38 ± 3 g/kg0.75 for pudu and 76 ± 5 g/kg0.75 for muntjac) was higher, and the mean retention times (MRT) correspondingly shorter (e.g., MRT small particles in the total digestive tract 39 ± 8 h for pudu and 15 ± 2 h for muntjac), in the muntjac. The SF for small particles/liquid in the reticulorumen were, however, similar for both species, at 1.47 ± 0.21 for pudu and 1.66 ± 0.20 for muntjac, indicating a 'moose-type' physiology for both, irrespective of their different phylogenetic origin. To date, SF recorded in bovids attain distinctively higher values than the few reported for cervids. This situation reflects the degree of hypsodonty (tooth crown height) attained by these taxa, which is higher in bovids than in cervids. Together, constraints in hypsodonty as well as SF might limit cervids to more mesic habitats without distinct loads of external abrasives (such as dust or grit) on their food. In both species, some animals showed the typical ruminant pattern of a longer MRT for large than for small particle markers, but in some animals, this difference was not evident. This may be due to variable degrees of marker chewing during ingestion.

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-pregnant sheep (74 ± 10 kg) were fed a hay-only diet in a 3 × 3 Latin square design with oral doses of 0, 2.5 and 5 mg pilocarpine/kg body weight and day. Measurements included feed and water intake, MRT of liquid and particulate phases in the reticulorumen (RR) and total gastrointestinal tract (GIT), ruminal microbial yield (via urinary purine bases and metabolic faecal nitrogen), total tract methane emission, apparent nutrient digestibility and rumen fluid parameters. Data were investigated for linear and quadratic effects using orthogonal polynomial contrasts. The MRT of liquid and small particles in the RR and total GIT, and the short-chain fatty acid concentration in rumen fluid, linearly declined with increasing pilocarpine dosage, while no quadratic relationship was detected. Intake of feed DM and water, apparent nutrient digestibility, methane yield and microbial yield were not affected by pilocarpine. When combining the sheep data with that of a similar experiment in cattle, we found that the MRT of the liquid phase was positively associated with estimated NDF digestibility and with methane production per digested NDF, but was not associated with microbial yield or the ratio of acetate to propionate. The ratio between MRT of the particulate and the liquid phase was smaller for sheep than that for cattle, and was not affected by treatment. Differences in this ratio might explain why species reacted differently to the saliva-inducing agent, which might help to explain the discrepancy between species in the effect of induced saliva flow on digestive parameters.

Wildlife parasite communities are important for an OneHealth approach. The external environment impacts host-associated communities directly and via the hosts. Hosts in poor body condition are more susceptible to infection and parasite mode of transmission will affect occurrence: rural environments with better availability of intermediate hosts favour trophic transmission, while urban environments, often with dense host populations, favour direct transmission. We here study helminth communities within their synanthropic red fox (Vulpes vulpes) hosts (155 intestinal samples) using DNA metabarcoding of multiple marker genes (18S rRNA, 28S rRNA, COI). Controlling for sampling bias by incorporating DNA quantity and quality into models, we analysed the effect of environmental (urbanisation, seasonality) and host-intrinsic (weight, age, sex) variables on helminth communities. Helminth diversity was increased in younger hosts, in foxes with lower body weight and in those found in winter and spring. Host intrinsic drivers had smaller effects on the composition of the community, which was impacted by urbanisation, dependent on parasite transmission mode: surprisingly, transmission in two-host lifecycles was more pronounced in urban Berlin than in rural Brandenburg. Our results disagree with the prevailing hypothesis that trophically transmitted helminths are less prevalent in urban areas than in rural areas. Environmental drivers, i.e. urbanisation, affected each helminth species in the community differently, and we cannot generalise from helminth traits to their occurrences in urbanised areas. Finding co-infestations with multiple helminths and high infection intensity associated with poor body condition, however, might be relevant for a OneHealth approach.

Abstract 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 (6.81 kg dry matter/day) of grass hay. Passage markers representing the liquid (Co‐EDTA) as well as the particulate digesta phase (Yb—undefined; Cr mordanted fibre 1−2 mm; Ce‐mordanted fibre 8 mm) were given as a pulse‐dose into the cannula to measure their mean retention times (MRT). The MRTs were compared by repeated‐measurements analysis of variance. The MRT in the hindgut was 22.2 ± 2.4 h for Co, 25.0 ± 3.4 h for Yb, 26.2 ± 1.6 h for Cr and 26.3 ± 1.5 h for Ce. Whereas differences between the particle marker MRTs were not significant (p adj. > 0.05), significant differences were observed between the solute marker Co and each of the particle markers Cr and Ce (p adj. < 0.009). The results confirm the well‐known significant, albeit small, difference in MRT in horses between the fluid and the particle digesta phase, and corroborate another recent study that used a combination of whole, marked hay and individual marker analysis in different particle size fractions of the faeces, which also did not detect a selective retention of any particle size class.

Spatial and temporal variability in the availability of food resources will lead to variation in a species’ diet, which can then influence patterns of space use, sociality, and life history characteristics. Despite such potential impacts, little information is available about dietary variability for some species with large geographical ranges. Here we quantify the diet and nutritional content of plants consumed by western lowland gorillas (Gorilla gorilla gorilla) in Loango National Park, Gabon over a 2.6 year period and make comparisons with two study sites located 800 km away. The major foods consumed by the Loango gorillas differed greatly from the other two study sites, but gorillas at all three locations spent a similar proportion of feeding time consuming herbaceous vegetation and tree leaves (~ 50%) and fruit (35%). The Loango gorillas spent approximately 10% of feeding time eating nuts, which were not consumed at the other two study sites. Gorillas at those sites spent about 5% of feeding time eating insects, which were not consumed by Loango gorillas. Even though the species composition of the diet differed among the three sites, the nutritional composition of the major food items differed very little, suggesting that western gorillas consume foods of similar nutritional values to meet their dietary needs. This study shows the flexibility of diet of a species with a wide geographic distribution, which has implications for understanding variation in life history characteristics and can be useful for conservation management plans.

Studying species interactions and niche segregation under human pressure provides important insights into species adaptation, community functioning and ecosystem stability. Due to their high plasticity in behaviour and diet, urban mesocarnivores are ideal species for studying community assembly in novel communities. We analysed the spatial and temporal species interactions of an urban mesocarnivore community composed of the red fox Vulpes vulpes and the marten Martes sp. as native species, the raccoon Procyon lotor as invasive species, and the cat Felis catus as a domestic species in combination with human disturbance modulated by the SARS-CoV-2 lockdown effect that happened while the study was conducted. We analysed camera trap data and applied a joint species distribution model to understand not only the environmental variables influencing the detection of mesocarnivores and their use intensity of environmental features but also the species' co-occurrences while accounting for environmental variables. We then assessed whether they displayed temporal niche partitioning based on activity analyses, and finally analysed at a smaller temporal scale the time of delay after the detection of another focal species. We found that species were more often detected and displayed a higher use intensity in gardens during the SARS-CoV-2 lockdown period, while showing a shorter temporal delay during the same period, meaning a high human-induced spatiotemporal overlap. All three wild species spatially co-occurred within the urban area, with a positive response of raccoons to cats in detection and use intensity, whereas foxes showed a negative trend towards cats. When assessing the temporal partitioning, we found that all wild species showed overlapping nocturnal activities. All species displayed temporal segregation based on temporal delay. According to the temporal delay analyses, cats were the species avoided the most by all wild species. To conclude, we found that although the wild species were positively associated in space, the avoidance occurred at a smaller temporal scale, and human pressure in addition led to high spatiotemporal overlap. Our study sheds light to the complex patterns underlying the interactions in a mesocarnivore community both spatially and temporally, and the exacerbated effect of human pressure on community dynamics.

Frugivorous primates have developed several strategies to deal with wild fruit scarcity, such as modifying their activity budget or enlarging their diet. Agricultural expansion threatens primate habitats and populations (e.g., disease transmission, agrochemical exposure), but it also increases crop feeding opportunities. We aimed at understanding whether maize presence close to the natural habitat of chimpanzees, a threatened species, would lead to significant behavioral modifications. We monitored 20 chimpanzees over 37 months in Kibale National Park, Uganda, with maize gardens at the forest edge. Based on focal nest-to-nest data, we analyzed their diet, activity budget, and energy balance depending on wild fruit and maize availability. We found that the Sebitoli area is a highly nutritive habitat for chimpanzees, with large and caloric wild fruits available all year long. The chimpanzees opportunistically consume maize and exploit it by resting less during maize season. However, no significant variation was found in daily paths and energy expenditures according to maize availability. No behavioral or energy modification was observed regarding wild resources either. Despite the availability of nutritious domestic resources, chimpanzees still exploit wild fruits and do not limit their movements. Thus, their contribution to seed dispersal and forest regeneration in this area is not affected.

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 saliva stimulant in cattle to investigate the effect of different individual chewing behaviour on fluid and particle MRT with a consistent diet. Four non-lactating cattle (670-850 kg body mass [BM]) were used in a 4 × 4 Latin square design, treated with the saliva stimulant pilocarpine in dosages of 0, 1, 2.5 and 5 mg/kg BM per day. The cattle were fed hay with dry matter intake (DMI) assigned according to their metabolic body weight. MRT in the whole gastrointestinal tract (GIT), the reticulorumen (RR) and the distal tract were measured using Co-EDTA, Cr-mordanted fibre and La-mordanted fibre as markers representing fluid, small particles (2 mm) and large particles (1 cm), respectively. The chewing behaviour was measured via noseband pressure sensor and expressed as chewing frequency (chews per time) and chewing intensity (chews per DMI), both for total chewing (ingestion plus rumination) and rumination chewing alone. The animals differed considerably in chewing behaviour and MRT measures. BM did not show a significant effect on chewing behaviour and MRT measures, though it tended to negatively correlated to total chewing intensity. Chewing intensity exerted a significant negative influence on MRT of fluid and particles in the RR, which was not the case for chewing frequency. Chewing frequency showed a significant relationship with MRT of large particles in the GIT. We suggest that chewing behaviour could influence MRT in two ways: (i) by affecting saliva production via the masticatory-salivary reflex and subsequently, the fluid inflow to the RR; (ii) by contributing to particle size reduction. Should the link between chewing behaviour and MRT be corroborated in larger studies, chewing measures, with their large interindividual variation, could emerge as an easy-to-measure proxy for MRT characteristics.

The inactivation of ancestral protein-coding genes (gene loss) can be associated with phenotypic modifications. Within placental mammals, repeated losses of PNLIPRP1 (gene inhibiting fat digestion) occurred preferentially in strictly herbivorous species, whereas repeated NR1I3 losses (gene involved in detoxification) occurred preferentially in strictly carnivorous species. It was hypothesized that lower fat contents of herbivorous diets and lower toxin contents of carnivorous diets cause relaxed selection pressure on these genes, resulting in the accumulation of mutations and ultimately to convergent gene losses. However, because herbivorous and carnivorous diets differ vastly in their composition, a fine-grained analysis is required for hypothesis testing. We generated a trait matrix recording diet and semi-quantitative estimates of fat and toxin consumption for 52 placental species. By including data from 31 fossil taxa, we reconstructed the ancestral diets in major lineages (grundplan reconstruction). We found support that PNLIPRP1 loss is primarily associated with low levels of fat intake and not simply with herbivory/carnivory. In particular, PNLIPRP1 loss also occurred in carnivorous lineages feeding on a fat-poor diet, suggesting that the loss of this gene may be beneficial for occupying ecological niches characterized by fat-poor food resources. Similarly, we demonstrated that carnivorous species are indeed less exposed to diet-related toxins, suggesting that the loss of NR1I3 and related genes (NR1I2 and UGT1A6) resulted from relaxed selection pressure. This study illustrates the need of detailed phenotype studies to obtain a deeper understanding of factors underlying gene losses and to progress in understanding genomic causes of phenotypic variation in mammals.

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 animals, we applied a saliva stimulant, pilocarpine, to modify liquid flow rate in cattle. Four non-lactating cows (750 ± 71 kg) were fed forage only (restricted to constant intake) in a 4 × 4 Latin square design with oral doses of 0, 1, 2.5 and 5mg pilocarpine/kg body weight and day. We quantified feed and water intake, ruminal and total tract mean retention time (MRT) of solute and particle markers, ruminal microbial yield (via urinary purine bases or metabolic faecal nitrogen), CH4 emission, digestibility, chewing behaviour, reticular motility and rumen fluid parameters. The effect of induced saliva flow was evident by visibly increased salivation and water intake. Increasing the pilocarpine dosages resulted in a linearly decreased MRT of fluid and small particles (p < 0.001 and p< 0.05, respectively) and methane yield as related to digested DM (p < 0.05), the latter at a magnitude of 5%. No effect of treatment was found on ruminal microbial yield estimated via purine derivates. Metabolic faecal N as an indicator of microbial growth linearly correlated with pilocarpine dosages (p < 0.05). No significant relationship was found between pilocarpine dosages and large particle MRT, nutrient digestibility, ruminal pH and short-chain fatty acids. In conclusion, different from some in vitro studies, there was little indication of a reciprocal effect of CH4 and microbial biomass production in cows fed a forage-only diet.

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 other hand, reports on relatively small salivary glands, susceptibility to negative effects of tannins, and a putative absence of tannin-binding salivary proteins would suggest the greater kudu to be an exceptional browser with a 'cattle-type' digestive physiology. We measured MRT in four zoo-kept greater kudu females, which resulted in a MRTparticleRR/MRTfluidRR ratio between 1.07-1.43, well within the range of 'moose-type' ruminants and similar to eland (Taurotragus oryx). In this regard, consistent morphophysiological studies on greater kudu are required to resolve the seemingly contradictory findings in this species.

Abstract Numerous studies have examined whether the primary and/or secondary sex ratio in mammals, including humans, deviates from an equilibrium of 1:1. Although effect size in the sex ratio variation is expected to be low, a large sample size allows the identification of even small deviations from parity. In this study, we investigated whether the sex ratio of roe deer (Capreolus capreolus) offspring at birth approaches parity, using a large data set from roe deer offspring tagged in Baden‐Württemberg (Germany, 1972–2019, N = 12,437). In addition, a systematic re‐analysis of available data on the secondary sex ratios of roe deer was conducted to test whether our finding withstood the accumulation of further data. The null hypothesis that the sex ratio of roe deer (prenatal sex ratio and sex ratio at birth) approaches parity was rejected. Moreover, the secondary sex ratio of roe deer offspring deviated from the male‐biased mean for relatively cold or warm weather conditions during autumn and winter. Our study provides strong evidence for a male‐biased sex ratio in a large herbivore and weak evidence for variations in the secondary sex ratio owing to environmental conditions. The pattern is highly relevant in the context of climate change and its impact on the population dynamics of large herbivores.

Background Animal personality has emerged as a key concept in behavioral ecology. While many studies have demonstrated the influence of personality traits on behavioral patterns, its quantification, especially in wild animal populations, remains a challenge. Only a few studies have established a link between personality and recurring movements within home ranges, although these small-scale movements are of key importance for identifying ecological interactions and forming individual niches. In this regard, differences in space use among individuals might reflect different exploration styles between behavioral types along the shy-bold continuum. Methods We assessed among-individual differences in behavior in the European hare (Lepus europaeus), a characteristic mammalian herbivore in agricultural landscapes using a standardized box emergence test for captive and wild hares. We determined an individuals' degree of boldness by measuring the latencies of behavioral responses in repeated emergence tests in captivity. During capture events of wild hares, we conducted a single emergence test and recorded behavioral responses proven to be stable over time in captive hares. Applying repeated novel environment tests in a near-natural enclosure, we further quantified aspects of exploration and activity in captive hares. Finally, we investigated whether and how this among-individual behavioral variation is related to general activity and space use in a wild hare population. Wild and captive hares were treated similarly and GPS-collared with internal accelerometers prior to release to the wild or the outdoor enclosure, respectively. General activity was quantified as overall dynamic body acceleration (ODBA) obtained from accelerometers. Finally, we tested whether boldness explained variation in (i) ODBA in both settings and (ii) variation in home ranges and core areas across different time scales of GPS-collared hares in a wild population. Results We found three behavioral responses to be consistent over time in captive hares. ODBA was positively related to boldness (i.e., short latencies to make first contact with the new environment) in both captive and wild hares. Space use in wild hares also varied with boldness, with shy individuals having smaller core areas and larger home ranges than bold conspecifics (yet in some of the parameter space, this association was just marginally significant). Conclusions Against our prediction, shy individuals occupied relatively large home ranges but with small core areas. We suggest that this space use pattern is due to them avoiding risky, and energy-demanding competition for valuable resources. Carefully validated, activity measurements (ODBA) from accelerometers provide a valuable tool to quantify aspects of animal personality along the shy-bold continuum remotely. Without directly observing-and possibly disturbing-focal individuals, this approach allows measuring variability in animal personality, especially in species that are difficult to assess with experiments. Considering that accelerometers are often already built into GPS units, we recommend activating them at least during the initial days of tracking to estimate individual variation in general activity and, if possible, match them with a simple novelty experiment. Furthermore, information on individual behavioral types will help to facilitate mechanistic understanding of processes that drive spatial and ecological dynamics in heterogeneous landscapes.