Interspecific association between two primatespecies in an urban park / Associação interespecífica entre duas espécies de primatas em um parque urbano

As with Amazonian primates, mixed associations between species in the Atlantic Forest are also influenced by ecological factors. However, Atlantic Forest primates may face additional challenges, such as isolation pressures and fragmentation of forest habitats, which may increase the frequency of these arrangements. The main of this work is to report a sympatry with possible interaction between individuals of two species of primates of the Pitheciidae and Callitrichidae families: Callicebus nigrifrons (Spix 1823) and Callithrix aurita (É. Geoffroy Saint-Hilaire 1812) in an urban park in the south of the state of Minas Gerais. Individuals were observed interacting during foraging and displacement. The association of individuals of the two species can be explained by the low quality of the forest fragment, as it can increases the chances of obtaining food resources and configures a dilution strategy against predator attacks.

Assim como ocorre com os primatas amazônicos, as associações mistas entre espécies na Mata Atlântica também são influenciadas por fatores ecológicos. No entanto, os primatas da Mata Atlântica podem enfrentar desafios adicionais, como pressões de isolamento e fragmentação de habitats florestais, que podem aumentar a frequência desses arranjos. O objetivo deste trabalho é apresentar um relato de simpatia com possível interação entre indivíduos de duas espécies de primatas das famílias Pitheciidae e Callitrichidae: Callicebus nigrifrons (Spix 1823) e Callithrix Resumo aurita (É. Geoffroy Saint-Hilaire 1812) em um parque urbano no sul do estado de Minas Gerais. Foram observados indivíduos interagindo durante o forrageio e deslocamento. A associação de indivíduos das duas espécies pode ser explicada devido à baixa qualidade do fragmento florestal, pois pode aumentar as chances de obter recursos alimentares e configura uma estratégia de diluição de contra-ataques de predadores.

Deep learning detects subtle facial expressions in a multilevel society primate.

Facial expressions in nonhuman primates are complex processes involving psychological, emotional, and physiological factors, and may use subtle signals to communicate significant information. However, uncertainty surrounds the functional significance of subtle facial expressions in animals. Using artificial intelligence (AI), this study found that nonhuman primates exhibit subtle facial expressions that are undetectable by human observers. We focused on the golden snub-nosed monkeys (Rhinopithecus roxellana), a primate species with a multilevel society. We collected 3427 front-facing images of monkeys from 275 video clips captured in both wild and laboratory settings. Three deep learning models, EfficientNet, RepMLP, and Tokens-To-Token ViT, were utilized for AI recognition. To compare the accuracy of human performance, two groups were recruited: one with prior animal observation experience and one without any such experience. The results showed human observers to correctly detect facial expressions (32.1% for inexperienced humans and 45.0% for experienced humans on average with a chance level of 33%). In contrast, the AI deep learning models achieved significantly higher accuracy rates. The best-performing model achieved an accuracy of 94.5%. Our results provide evidence that golden snub-nosed monkeys exhibit subtle facial expressions. The results further our understanding of animal facial expressions and also how such modes of communication may contribute to the origin of complex primate social systems.

Mantled howler monkeys (Alouatta palliata) alter activity and spatial cohesion across a continuous forest and forest fragment in Costa Rica.

Habitat loss due to deforestation is a primary threat to global biodiversity. Clearing tropical rainforests for agriculture or development leads to forest fragmentation. Forest fragments contain fewer large trees and provide lower food availability for primates compared to continuous forests. Mantled howler monkeys (Alouatta palliata) inhabit fragmented rainforests and may need to alter their activity budgets and spatial cohesion to mitigate competition and conserve energy in fragments where food quality is lower. We compared howler monkey activity and spatial cohesion across a small forest fragment (La Suerte Biological Research Station, LSBRS) and a large, continuous forest (La Selva Research Station) in Costa Rica. We predicted that monkeys at LSBRS would rest more, feed more, travel less, and be less spatially cohesive compared to La Selva to contend with fewer resources in the small fragment. Using instantaneous scan sampling at 2-min intervals during 30-min focal samples, we recorded activity and the number of individuals within 5 m of the focal animal. We collected 1505 h of data from 2017-2024. Monkey activity and spatial cohesion differed significantly across sites. As predicted, monkeys at LSBRS spent more time feeding than at La Selva, but contrary to our predictions, they rested less and traveled more. The mean number of individuals within 5 m was significantly lower at LSBRS compared to La Selva. The ability to modify their activity and spatial cohesion in response to fragmentation provides insight into how primates can contend with fewer resources and higher competition in changing ecosystems worldwide.

Craniomandibular variation in the endemic Hispaniolan primate, Antillothrix bernensis.

Here we describe new fossil material of Antillothrix bernensis, a Pleistocene-Holocene primate taxon from Hispaniola. It is now represented by seven crania, five mandibles, and dozens of postcranial elements from several paleontologically rich cave systems. The five adult crania included here share a similar overall profile as well as specific features such as a deep depression at the glabella. The complete anterior dentition of Antillothrix can now be described for the first time; short canine crowns, in the apicobasal dimension, compare well with titi monkeys, but the new crania and mandibles lack the specialized tall-crowned incisors of the extant pitheciids. They do, however, have a diastema between the lateral maxillary incisors and canines, a feature not present in the previously known crania. The new mandibles deepen posteriorly and have a medial inflection of the mandibular ramus, as in some pitheciids, but also share with Xenothrix a significant vertical narrowing of the corpus under P4/M1 not observed among extant taxa. Two of the specimens, a cranium and a mandible that do not fit together, exhibit congenitally absent third molars-a rarity among extant, noncallitrichine taxa. There is an approximately 1-kg range in the estimated body mass among the full Antillothrix sample (from 2.4 to 3.4 kg), as well as a range of approximately 5 cm3 of endocranial volume (from 40 to 45 cm3). With these extended ranges from the new specimens, Antillothrix can no longer be described as a taxon with a brain size smaller than that expected for its body size. Neither of these ranges in the brain size or body size is large enough to indicate a substantial level of sexual dimorphism or to necessitate separating the sample into male and female individuals. Given this, and the similar canine sizes for all specimens where they are present, the sample is consistent with a morphologically variable but monomorphic species.

Evidence for interacting but decoupled controls of decisions and movements in non-human primates.

Many recent studies indicate that control of decisions and actions is integrated during interactive behavior. Among these, several carried out in humans and monkeys conclude that there is a co-regulation of choices and movements. Another perspective, based on human data only, proposes a decoupled control of decision duration and movement speed, allowing for instance to trade decision duration for movement duration when time pressure increases. Crucially, it is not currently known whether this ability to flexibly dissociate decision duration from movement speed is specific to humans, whether it can vary depending on the context in which a task is performed, and whether it is stable over time. These are important questions to address, especially to rely on monkey electrophysiology to infer the neural mechanisms of decision-action coordination in humans. To do so, we trained two macaque monkeys in a perceptual decision-making task and analyzed data collected over multiple behavioral sessions. Our findings reveal a strong and complex relationship between decision duration and movement vigor. Decision duration and action duration can co-vary but also "compensate" each other. Such integrated but decoupled control of decisions and actions aligns with recent studies in humans, validating the monkey model in electrophysiology as a means of inferring neural mechanisms in humans. Crucially, we demonstrate for the first time that this control can evolve with experience, in an adapted manner. Together, the present findings contribute to deepening our understanding of the integrated control of decisions and actions during interactive behavior.

No birth-associated maternal mortality in Japanese macaques (Macaca fuscata) despite giving birth to large-headed neonates.

Human fetuses at term are large relative to the dimensions of the maternal birth canal, implying that their birth can be associated with difficulties. The tight passage through the human birth canal can lead to devastating outcomes if birth becomes obstructed, including maternal and fetal death. Although macaques have to accommodate similarly large fetuses, relative to their maternal birth canals, it was not known whether macaque mothers face birth difficulties similar to humans. Based on 27 y of demographic data from a semi-free-ranging, closely monitored population of Japanese macaques (Macaca fuscata), we found no birth-associated mortality in macaques. This differs from the situation in many human populations. We suggest three nonmutually exclusive hypotheses to explain these observations. i) The macaque fetal skull is similarly flexible as the human fetal skull. ii) The macaque pelvis and connective tissue show greater flexibility during birth. iii) The interplay between macaque pelvic shape and birth dynamics is smoother and incurs fewer complications than in humans.

Domestic chicken predation and prey sharing by urban capuchin monkeys (Sapajus sp.).

Capuchin monkeys are omnivorous platyrrhines with a high frequency of faunivory and can survive in urban forest fragments. Predation of wild vertebrates (high-quality foods) by capuchin monkeys has been frequently reported in many species of Cebus and Sapajus. However, predation of domestic animals is unknown. We describe a rare episode of predation, consumption, and sharing of an adult domestic chicken (Gallus gallus domesticus) by individuals from a social group of robust capuchin monkeys (Sapajus sp.) living in a small urban park in the city of Foz do Iguaçu, southern Brazil. This relatively large prey is freely farmed at the study site. The capture, slaughter, preparation (removal of feathers from the body), and consumption of the prey by the capuchins lasted 22 min. The dominant adult male ate the chicken's head and tolerated the approach of two juveniles. The juveniles shared the remainder of the prey after the adult abandoned it. These juveniles scared other group members that approached the carcass. We recorded an opportunistic hunt for easily accessible domestic prey, a case of human resource use by urban primates that shared passively the atypical and valuable food. Though a rare event, the predation on a domestic animal indicates a potential source of conflict with humans that can have negative impacts on urban primates.

Monitoring of Leishmania infantum in captive non-human primates in Spain.

Cases of Leishmania infantum infection have recently been reported in non-human primates (NHPs) in Spain causing severe clinical disease in critically endangered orangutans (Pongo pygmaeus pygmaeus). The aim of this study was to determine exposure and risk factors associated with L. infantum infection in NHPs housed in zoos and wildlife rescue centers (WRC) in Spain. Between 2007 and 2023, sera from 252 NHPs belonging to 47 different species were collected at 15 centers. Indirect immunofluorescence was used to detect the presence of antibodies against L. infantum (cut-off ≥1:80). In addition, hair samples from 78 individuals were tested for Leishmania kDNA by real-time quantitative PCR (qPCR). Anti-Leishmania antibodies were detected in 4.0 % (10/252; 95 %CI: 1.6-6.4) of the NHPs tested at 26.7 % (4/15) of the centers sampled. Twenty-two NHPs were longitudinally sampled between 2010 and 2023: one ring-tailed lemur (Lemur catta) seroconverted and a seropositive orangutan increased antibody titers during the study period. Leishmania infantum kDNA was found in 62.8 % (49/78; 95 %CI: 52.1-73.6) of animals and at all centers sampled (100 %; 7/7). Phylogenetic analysis revealed high homology between the sequence obtained and strains previously isolated in humans, dogs and captive and free-living wildlife species in Spain. To the authors´ knowledge, this is the first report of Leishmania kDNA detection in NHP hair samples. The results indicate that hair samples could be a useful, non-invasive method of detection of L. infantum infection in these species. This is also the first large-scale survey of L. infantum conducted in NHP species in Europe. We report for the first time the presence of Leishmania kDNA in nine different NHP species belonging to the families Cercopithecidae, Lemuridae, and Hylobatidae, expanding the host range for this parasite. The main risk factors associated with L. infantum infection were: age (≥5 years old) and body size (large). Our results demonstrate widespread circulation of this parasite among NHPs housed in Spain, which could be of conservation and public health concern. Monitoring and control programs should be implemented in zoos and WRCs to minimize the risk of NHP exposure to L. infantum in endemic areas worldwide.

A 3D-Printed helmet for precise and repeatable neuromodulation targeting in awake non-human primates.

The application of non-invasive brain stimulation (NIBS) in non-human primates (NHPs) is critical for advancing understanding of brain networks and developing treatments for neurological diseases. Improving the precision of targeting can significantly enhance the efficacy of these interventions. Here, we introduce a 3D-printed helmet designed to achieve repeatable and precise neuromodulation targeting in awake rhesus monkeys, eliminating the need of head fixation. Imaging studies confirmed that the helmet consistently targets the primary motor cortex (M1) with a margin of error less than 1 mm. Evaluations of stimulation efficacy revealed high resolution and stability. Additionally, physiological evaluations under propofol anesthesia showed that the helmet effectively facilitated the generation of recruitment curves for motor area, confirming successful neuromodulation. Collectively, our findings present a straightforward and effective method for achieving consistent and precise NIBS targeting in awake NHPs, potentially advancing both basic neuroscience research and the development of clinical neuromodulation therapies.

Contributions and future potential of animal models for geroscience research on sensory systems.

Sensory systems mediate our social interactions, food intake, livelihoods, and other essential daily functions. Age-related decline and disease in sensory systems pose a significant challenge to healthy aging. Research on sensory decline in humans is informative but can often be difficult, subject to sampling bias, and influenced by environmental variation. Study of animal models, including mice, rats, rabbits, pigs, cats, dogs, and non-human primates, plays a complementary role in biomedical research, offering advantages such as controlled conditions and shorter lifespans for longitudinal study. Various species offer different advantages and limitations but have provided key insights in geroscience research. Here we review research on age-related decline and disease in vision, hearing, olfaction, taste, and touch. For each sense, we provide an epidemiological overview of impairment in humans, describing the physiological processes and diseases for each sense. We then discuss contributions made by research on animal models and ideas for future research. We additionally highlight the need for integrative, multimodal research across the senses as well as across disciplines. Long-term studies spanning multiple generations, including on species with longer life spans, are also highly valuable. Overall, integrative studies of appropriate animal models have high translational potential for clinical applications, the development of novel diagnostics, therapies, and medical interventions and future research will continue to close gaps in these areas. Research on animal models to improve understanding of the biology of the aging senses and improve the healthspan and additional research on sensory systems hold special promise for new breakthroughs.

Age-related physiological dysregulation progresses slowly in semi-free-ranging chimpanzees.

Background and objectives: Lifestyle has widespread effects on human health and aging. Prior results from chimpanzees (Pan troglodytes), one of humans' closest evolutionary relatives, indicate that these lifestyle effects may also be shared with other species, as semi-free-ranging chimpanzees fed a naturalistic diet show healthier values in several specific health biomarkers, compared with their sedentary, captive counterparts. Here, we examined how lifestyle factors associated with different environments affect rates of physiological aging in closely related chimpanzees. Methodology: We compared physiological dysregulation, an index of biological aging, in semi-free-ranging chimpanzees in an African sanctuary versus captive chimpanzees in US laboratories. If the rate of aging is accelerated by high-calorie diet and sedentism, we predicted greater age-related dysregulation in the laboratory populations. Conversely, if costs of a wild lifestyle accelerate aging, then semi-free-ranging chimpanzees at the sanctuary, whose environment better approximates the wild, should show greater age-related dysregulation. We further tested whether dysregulation differed based on sex or body system, as in humans. Results: We found that semi-free-ranging chimpanzees showed lower overall dysregulation, as well as lower age-related change in dysregulation, than laboratory chimpanzees. Males experienced lower dysregulation than females in both contexts, and the two populations exhibited distinct aging patterns based on body system. Conclusions and implications: Our results support the conclusion that naturalistic living conditions result in healthier aging in chimpanzees. These data provide support for the proposal that lifestyle effects on human health and aging are conserved from deeper into our evolutionary history.

Multimodal sexual signals are not precise indicators of fertility in female Kinda baboons.

Female fertility signals are found across taxa, and the precision of such signals may be influenced by the relative strength of different sexual selection mechanisms. Among primates, more precise signals may be found in species with stronger direct male-male competition and indirect female mate choice, and less precise signals in species with stronger indirect male-male competition (e.g. sperm competition) and direct female mate choice. We tested this hypothesis in a wild population of Kinda baboons in Zambia, combining data on female signals with reproductive hormones (estrogen and progesterone metabolites) and intra- and inter-cycle fertility. We predicted that Kinda baboons will exhibit less precise fertility signals than other baboon species, as they experience weaker direct and stronger indirect male-male competition. The frequency of copulation calls and proceptive behavior did not vary with hormones or intra- or inter-cycle fertility in almost all models. Sexual swelling size was predicted by the ratio of estrogen to progesterone metabolites, and was largest in the fertile phase, but differences in size across days were small. Additionally, there was variability in the timing of ovulation relative to the day of sexual swelling detumescence across cycles and swelling size did not vary with inter-cycle fertility. Our results suggest that female Kinda baboon sexual swellings are less precise indicators of fertility compared to other baboon species, while signals in other modalities do not reflect variation in intra- and inter-cycle fertility. Female Kinda baboon sexual signals may have evolved as a strategy to reduce male monopolizability, allowing for more female control over reproduction by direct mate choice.

Gastrointestinal Parasites in Non-Human Primates in Zoological Gardens in Northern Italy.

Non-human primates (NHPs) host a variety of helminth and protist parasites that are able to cause infection in humans. Gastrointestinal parasites in NHPs living in two zoological gardens of Northern Italy were studied. An total of 96 faecal pools were collected from 26 groups of NHPs. The mini-Flotac method was applied to fecal samples to detect gastrointestinal helminthiases, while the detection of the protists Cryptosporidium spp., Blastocystis sp. and Giardia duodenalis was performed by targeting SSU rRNA through nested PCR and real-time PCR; they were further studied by sequencing the same gene for Blastocystis and ßgiardine and triosephosphate isomerase (TPI) genes for Giardia. Twenty-two out of the 96 examined fecal pools (22.9%) were positive for one or more helminth species, including Hymenolepis diminuta, Trichurid, Capillariid and Strongylid eggs. All samples were negative for Cryptosporidium spp., while 16/26 (61.5%) animals were positive for G. duodenalis in the real-time PCR; the sequences obtained assigned them all to sub-assemblage BIV. Blastocystis sp. was detected in 22/26 of the NHPs (84.6%); molecular analyses attributed the isolates to ST 4, allele 92. Analyses of the feces of sympatric rats revealed the presence of the same allele, as well as of Hymenolepis diminuta eggs, raising concern about their role as parasite reservoirs in the facilities.

Commentary: Early-in-life Isoflurane Exposure Alters Resting-State Functional Connectivity in Juvenile Non-human Primates - a Role for Neuroinflammation?

The concern about anesthesia-induced developmental neurotoxicity (AIDN) in infants and young children arises from animal studies indicating potential long-term neurobehavioral impairments following early-in-life anesthesia exposure. While initial clinical studies provided ambiguous results, recent prospective assessments in children indicate associations between early-in-life anesthesia exposure and later behavioral alterations. Ethical constraints and confounding factors in clinical studies pose challenges in establishing a direct causal link and in investigating its mechanisms. This commentary on a recent study in non-human primates (NHPs) focuses on exploring the role of neuroinflammation and alterations in brain functional connectivity in the behavioral impairments following early-in-life anesthesia exposure. In juvenile NHPs, chronic astrogliosis in the amygdala correlates with alterations in functional connectivity between this area with other regions of the brain and with the behavioral impairments, suggesting a potential mechanism for AIDN. Despite acknowledging the study's limitations, these findings emphasize the need for further research with larger cohorts to confirm these associations and to establish a causal link between the neuroinflammation and the behavioral alterations associated with early-in-life anesthesia exposure.

Evaluating Methods for the Prediction of Cell Type-Specific Enhancers in the Mammalian Cortex.

Identifying cell type-specific enhancers in the brain is critical to building genetic tools for investigating the mammalian brain. Computational methods for functional enhancer prediction have been proposed and validated in the fruit fly and not yet the mammalian brain. We organized the 'Brain Initiative Cell Census Network (BICCN) Challenge: Predicting Functional Cell Type-Specific Enhancers from Cross-Species Multi-Omics' to assess machine learning and feature-based methods designed to nominate enhancer DNA sequences to target cell types in the mouse cortex. Methods were evaluated based on in vivo validation data from hundreds of cortical cell type-specific enhancers that were previously packaged into individual AAV vectors and retro-orbitally injected into mice. We find that open chromatin was a key predictor of functional enhancers, and sequence models improved prediction of non-functional enhancers that can be deprioritized as opposed to pursued for in vivo testing. Sequence models also identified cell type-specific transcription factor codes that can guide designs of in silico enhancers. This community challenge establishes a benchmark for enhancer prioritization algorithms and reveals computational approaches and molecular information that are crucial for the identification of functional enhancers for mammalian cortical cell types. The results of this challenge bring us closer to understanding the complex gene regulatory landscape of the mammalian brain and help us design more efficient genetic tools and potential gene therapies for human neurological diseases.

Ventral frontostriatal circuitry mediates the computation of reinforcement from symbolic gains and losses.

Reinforcement learning (RL), particularly in primates, is often driven by symbolic outcomes. However, it is usually studied with primary reinforcers. To examine the neural mechanisms underlying learning from symbolic outcomes, we trained monkeys on a task in which they learned to choose options that led to gains of tokens and avoid choosing options that led to losses of tokens. We then recorded simultaneously from the orbitofrontal cortex (OFC), ventral striatum (VS), amygdala (AMY), and mediodorsal thalamus (MDt). We found that the OFC played a dominant role in coding token outcomes and token prediction errors. The other areas contributed complementary functions, with the VS coding appetitive outcomes and the AMY coding the salience of outcomes. The MDt coded actions and relayed information about tokens between the OFC and VS. Thus, the OFC leads the processing of symbolic RL in the ventral frontostriatal circuitry.

Evaluating Thermal Infrared Drone Flight Parameters on Spider Monkey Detection in Tropical Forests.

Geoffroy's spider monkeys, an endangered, fast-moving arboreal primate species with a large home range and a high degree of fission-fusion dynamics, are challenging to survey in their natural habitats. Our objective was to evaluate how different flight parameters affect the detectability of spider monkeys in videos recorded by a drone equipped with a thermal infrared camera and examine the level of agreement between coders. We used generalized linear mixed models to evaluate the impact of flight speed (2, 4, 6 m/s), flight height (40, 50 m above ground level), and camera angle (-45°, -90°) on spider monkey counts in a closed-canopy forest in the Yucatan Peninsula, Mexico. Our results indicate that none of the three flight parameters affected the number of detected spider monkeys. Agreement between coders was "substantial" (Fleiss' kappa coefficient = 0.61-0.80) in most cases for high thermal-contrast zones. Our study contributes to the development of standardized flight protocols, which are essential to obtain accurate data on the presence and abundance of wild populations. Based on our results, we recommend performing drone surveys for spider monkeys and other medium-sized arboreal mammals with a small commercial drone at a 4 m/s speed, 15 m above canopy height, and with a -90° camera angle. However, these recommendations may vary depending on the size and noise level produced by the drone model.

SARS-CoV-2 infection perturbs the gastrointestinal tract and induces modest microbial translocation across the intestinal barrier.

SARS-CoV-2 infects via the respiratory tract, but COVID-19 includes an array of non-respiratory symptoms, among them gastrointestinal (GI) manifestations such as vomiting and diarrhea. Here we investigated the GI pathology of SARS-CoV-2 infections in rhesus macaques and humans. Macaques experienced mild infection with USA-WA1/2020 and shed viral RNA in the respiratory tract and stool, including subgenomic RNA indicative of replication in the GI tract. Intestinal immune cell populations were disturbed, with significantly fewer proliferating (Ki67+) jejunal B cells in SARS-CoV-2-infected macaques than uninfected ones. Modest translocation of bacteria/bacterial antigen was observed across the colonic epithelium, with a corresponding significant increase in plasma soluble CD14 (sCD14) that may be induced by LPS. Human plasma demonstrated significant decreases in interleukin (IL)-6 and sCD14 upon recovery from COVID-19, suggesting resolution of inflammation and response to translocated bacteria. sCD14 significantly positively correlated with zonulin, an indicator of gut barrier integrity, and IL-6. These results demonstrate that GI perturbations such as microbial translocation can occur in even mild SARS-CoV-2 infections and may contribute to the COVID-19 inflammatory state.IMPORTANCEThis study investigates gastrointestinal (GI) barrier disruption in SARS-CoV-2 infections and how it may contribute to disease. We observed bacteria or bacterial products crossing from the colon interior (the lumen) to the lamina propria during SARS-CoV-2 infection in macaques. Bacteria/bacterial products are tolerated in the lumen but may induce immune responses if they translocate to the lamina propria. We also observed a significant increase in soluble CD14, which is associated with an immune response to bacterial products. In addition, we observed that humans recovering from COVID-19 experienced a significant decrease in soluble CD14, as well as the inflammatory marker interleukin (IL)-6. IL-6 and sCD14 correlated significantly across macaque and human samples. These findings suggest that SARS-CoV-2 infection results in GI barrier disruption that permits microbial translocation and a corresponding immune response. These findings could aid in developing interventions to improve COVID-19 patient outcomes.

Analysis of mortality in François' langurs (Trachypithecus francoisi) managed care in Trachypithecus francoisi rare animal breeding Center in Wuzhou, Guangxi, China: a 16-year review.

In managed care settings, primates are susceptible to a variety of health complications. A comprehensive understanding of the causes of mortality and their association with management practices is essential for enhancing the welfare of managed care populations such as François' langurs (Trachypithecus francoisi). However, literature addressing prevalent diseases or causes of death in such settings remains limited among François' langurs in managed care. To address this knowledge gap, we conducted an analysis of mortality causes in François' langurs (n = 97) who died of natural causes during a 16-year period (2007-2022) at the Trachypithecus francoisi Rare Animal Breeding Center in Wuzhou, Guangxi, China. Morphological diagnosis and organ system and etiological evaluations were performed. François' langurs were divided into six age-range groups, following previous studies: infant (≤ 1 year old), juvenile (1 to 2 years), sub-adult (2 to 4 years), adult (4 to 10 years), middle-aged (10 to 15 years), and geriatric (> 15 years). Results revealed that the primary causes of mortality in managed care François' langurs were pneumonia (n = 11, 12.22%), neoplasia (n = 7, 7.78%), ileus (n = 7, 7.78%), senility (n = 6, 6.67%), gastroenteritis (n = 6, 6.67%), cardiac disease (n = 5, 5.56%), hemorrhage (n = 5, 5.56%), intestinal adhesion (n = 4, 4.44%), and renal abscess (n = 4, 4.44%). The gastrointestinal system was most frequently implicated in deaths, followed by the respiratory system (n = 17, 18.89%), multisystem disease (n = 16, 17.78%), and cardiovascular system (n = 15, 16.67%). Regarding etiology, infectious or inflammatory (n = 32, 35.56%) and physiological factors (n = 17, 18.89%) were identified as the leading contributors to the high mortality rate. It is imperative for managers to recognize the distinct risk profiles associated with different age groups. Specifically, pneumonia was the principal cause of death in infant and juvenile langurs, while renal disease, neoplasia, gastroenteritis, and intestinal obstruction were the primary causes of death in adult and middle-aged François' langurs and advanced age and cardiac disease were the main causes of death in geriatric langurs.

Why non-human primates are needed in stroke preclinical research.

Numerous seemingly promising cerebroprotectants previously validated in rodents almost all have failed in stroke clinical trials. The failure of clinical translation strikes an essential need to employ more ideal animal models in stroke research. Compared with the most commonly used rodent models of stroke, non-human primates (NHPs) are far more comparable to humans regarding brain anatomy, functionality and pathological features. The aim of this perspective was to summarise the advantages of NHPs stroke models over rodents, discuss the current limitations of NHPs models, and cast an outlook on the future development of NHPs in stroke preclinical research.