Captive Monkeys Research Articles

Occurrence and clinical significance of abnormal liver findings by ultrasound in captive owl monkeys.

Imaging diagnostic methods are essential for a complete understanding of the liver function and may aid in early detection of hepatic disorders. Sixty-nine owl monkeys were grouped in three age groups (AG): AG1 (<2years old, n=14), 2 (2-6years old, n=21), and 3 (>7years old, n=34). The animals were evaluated by ultrasound, liver function tests, and hemogram. The ultrasound revealed abnormal findings in the parenchyma ("starry sky" and steatosis) and/or in the gallbladder (cholelithiasis, septum, and wall edema) in 17 individuals, with higher incidence in AG3 individuals. Seven hepatic individuals showed alterations in the blood tests. Our study reported the occurrence of abnormal liver findings by ultrasound in owl monkeys and their associated clinical analyses. We recommend the regular use of ultrasound to evaluate liver condition in owl monkeys, particularly in old individuals.

Captivity and habituation to humans raise curiosity in vervet monkeys

The cognitive mechanisms causing intraspecific behavioural differences between wild and captive animals remain poorly understood. Although diminished neophobia, resulting from a safer environment and more “free” time, has been proposed to underlie these differences among settings, less is known about how captivity influences exploration tendency. Here, we refer to the combination of reduced neophobia and increased interest in exploring novelty as “curiosity”, which we systematically compared across seven groups of captive and wild vervet monkeys (Chlorocebus pygerythrus) by exposing them to a test battery of eight novel stimuli. In the wild sample, we included both monkeys habituated to human presence and unhabituated individuals filmed using motion-triggered cameras. Results revealed clear differences in number of approaches to novel stimuli among captive, wild-habituated and wild-unhabituated monkeys. As foraging pressure and predation risks are assumed to be equal for all wild monkeys, our results do not support a relationship between curiosity and safety or free time. Instead, we propose “the habituation hypothesis” as an explanation of why well-habituated and captive monkeys both approached and explored novelty more than unhabituated individuals. We conclude that varying levels of human and/or human artefact habituation, rather than the risks present in natural environments, better explain variation in curiosity in our sample of vervet monkeys.

Multi-Omics Analysis to Generate Hypotheses for Mild Health Problems in Monkeys.

Certain symptoms associated with mild sickness and lethargy have not been categorized as definitive diseases. Confirming such symptoms in captive monkeys (Macaca fascicularis, known as cynomolgus monkeys) can be difficult; however, it is possible to observe and analyze their feces. In this study, we investigated the relationship between stool state and various omics data by considering objective and quantitative values of stool water content as a phenotype for analysis. By examining the food intake of the monkeys and assessing their stool, urine, and plasma, we attempted to obtain a comprehensive understanding of the health status of individual monkeys and correlate it with the stool condition. Our metabolomics data strongly suggested that many lipid-related metabolites were correlated with the stool water content. The lipidomic analysis revealed the involvement of saturated and oxidized fatty acids, metallomics revealed the contribution of selenium (a bio-essential trace element), and intestinal microbiota analysis revealed the association of several bacterial species with the stool water content. Based on our results, we hypothesize that the redox imbalance causes minor health problems. However, it is not possible to make a definite conclusion using multi-omics alone, and other hypotheses could be proposed.

The potential interplay between the glandular microbiome and scent marking behavior in owl monkeys (Aotus nancymaae).

In mammals, scent marking behavior is a pervasive form of chemical communication that regulates social interactions within and between groups. Glandular microbiota consist of bacterial communities capable of producing chemical cues used in olfactory communication. Despite countless studies on scent marking in primates, few have examined the microbiota associated with glandular secretions. Nancy Ma's owl monkeys (Aotus nancymaae) are nocturnal, socially monogamous primates that frequently scent mark using their subcaudal glands. Previous analyses revealed that unique chemical signatures of Aotus may convey information about sex and age. We used positive reinforcement to sample the subcaudal glands of 23 captive owl monkeys to describe their glandular microbiomes and examine how patterns in these bacterial communities vary with age, sex, rearing environment and/or social group (pair identity). We coupled these analyses with behavioral observations to examine patterns in their scent marking behavior. We isolated 31 bacterial species from Phyla Firmicutes, Proteobacteria, and Actinobacteria, consistent with the dermal and glandular microbiomes of other primates. Several bacterial taxa we identified produce volatile organic compounds, which may contribute to olfactory communication. These bacterial communities are best predicted by an interaction between sex, rearing environment and pair identity rather than any of these variables alone. Within mated pairs of A. nancymaae, males and females scent mark their nest boxes at similar frequencies. In some pairs, rates of scent marking by males and females fluctuated over time in a similar manner. Pairs that had been together longer tended to exhibit the greatest similarities in their rates of scent marking. Together, these findings suggest that scent marking behavior and close social interactions with pair mates in Aotus may influence bacterial transmission and their glandular microbiomes. Chemical communication, including coordinated scent marking, may play a role in strengthening pair bonds, signaling pair status and/or in mate guarding in this socially monogamous primate.

The use of anogenital distance as a non-invasive predictor of seminal quality in captive squirrel monkey (Saimiri collinsi Osgood 1961).

Anogenital distance is considered a non-invasive measure to assess the development and functionality of sexual organs in different animal species. Hence, this measurement could potentially be used during the selection of non-human primates for reproductive biotechnology programs. The aim of this study was to assess the correlation between anogenital distance and reproductive parameters in captive Saimiri collinsi. Eight mature S.collinsi males were evaluated. Body weight, reproductive hormone levels, testicular volume, and seminal parameters were determined, and their relationship with anogenital distance measurements was assessed. Anogenital distance was correlated with seminal volume, sperm motility, vigor, and plasma membrane integrity, but not with body weight, reproductive hormones, and testicular volume. The determination of anogenital distance is a non-invasive method to predict seminal quality. This procedure has the advantage of providing andrologic information without a negative impact on animal welfare.

Hepatic lesions in captive owl monkeys (Aotus infulatus) with ultrasonographic "starry sky" liver.

The "starry sky" (SK) liver is ultrasonographic pattern characterized by multiple hyperechogenic foci in hepatic parenchyma. The study aimed to characterize the microscopic hepatic lesions in captive owl monkeys with SK liver. Thirty-seven clinically healthy owl monkeys had their liver scanned and 18 of them had liver biopsy. Animals with SK and peliosis hepatis (PH) were subjected to immunohistochemical and molecular screening for Bartonella spp. SK liver occurred in 59.4% (22/37) of the owl monkeys. Biopsied animals showed steatosis, hydropic degeneration, hemosiderosis, PH, and multifocal granulomatous hepatitis. Two monkeys had SK, granulomatous hepatitis, and PH which were negative for Bartonella spp. PH and granulomatous hepatitis associated with hepatocellular degenerative lesions may present as hyperechoic nodular liver lesions consisted of SK liver; therefore, concomitant occurrence of two lesions or more contributed to the hepatic SK pattern among owl monkeys and such cases might be clinically monitored.

Individualized Target Training Facilitated Transfer of Group Housed Capuchin Monkeys (Sapajus apella) to Test Cubicles and Discrimination of Targets on Computer Touch Screens.

Simple SummaryCoercion and non-voluntary procedures can cause fear, anxiety and maladaptive behaviors for captive animals, which makes animal husbandry and care more difficult and reduces animal welfare overall. Positive reinforcement training (i.e., using rewards for desired behaviors rather than punishment for undesirable behaviors) is shown to be beneficial in reducing animals’ fear responses and in encouraging voluntary cooperation across a wide range of species. This paper outlines two experiments in positive reinforcement training to understand the importance of individualized targets in facilitating the voluntary transfer of captive capuchin monkeys (Sapajus apella) from their group enclosure to individual test cubicles. Experiment 1, which assigned different colored and geometric targets to each animal, rewarded animals for touching and following their assigned target into their test cubicle. The animals rapidly acquired the ability to identify their target, ultimately allowing them to cooperate by moving from one space to another voluntarily. Experiment 2 rewarded animals for spontaneously identifying their assigned target among other animals’ targets and novel targets. The animals chose their target more often than predicted by chance, although they did make some errors.Animals in captivity often experience fear, anxiety and aggression during non-voluntary procedures, leading to adverse behaviors and ineffective outcomes for both animals and caretakers. Negative reinforcement and punishment, often due to ignorance regarding animal learning, can hurt animal welfare. However, voluntary participation through positive reinforcement training (PRT) can decrease stress related to these procedures and increase desired behaviors. Our goal was to demonstrate the positive effects of “target training” on animal welfare by training 10 captive capuchin monkeys (Sapajus apella) in two experiments designed to facilitate movement from a group home enclosure to a test cubicle. In Experiment 1, each monkey was assigned an individualized target (a unique shape/color combination). In daily training sessions, the animal was rewarded with a click-sounding stimulus and a food reinforcer for (a) touching the target, (b) following the respective target into a test cubicle, and (c) touching progressively smaller targets until progressing to digitized images on a computer touch screen. All 10 animals learned to approach and touch their individual physical target in one or two sessions and were able to successfully transition this behavior to an image of their target on a touch screen, although they made more errors with the touch screen. In Experiment 2, the animals were presented with other animals’ targets and novel targets. The seven animals in this experiment all touched their target at higher-than-chance rates in Trial 1 without explicit discrimination training, but only five reached the learning criteria for the task (>83% correct for three consecutive testing days. These results demonstrate that target training can make voluntary movement from group housing to test cubicles easier and benefit future animal care and procedures.

Profiling Humoral Immune Response Against Pre-Erythrocytic and Erythrocytic Antigens of Malaria Parasites Among Neotropical Primates in the Brazilian Atlantic Forest.

Human malaria due to zoonotic transmission has been recorded in the Atlantic Forest, an extra-Amazonian area in Brazil, which are a challenge for malaria control. Naturally acquired humoral immune response against pre-erythrocytic and erythrocytic antigens of Neotropical primates (NP) was evaluated here to improve the knowledge about the exposure of those animals to the malaria transmission and support the identification of the potential reservoirs of the disease in the Atlantic Forest. Blood samples of 154 monkeys from three areas of the Atlantic Forest were used to identify IgG antibodies against peptides of the repeat region of the major pre-erythrocytic antigen, the circumsporozoite protein (CSP), of Plasmodium vivax (PvCSP), Plasmodium brasilianum/Plasmodium malariae (Pb/PmCSP), and Plasmodium falciparum (PfCSP) by ELISA. Antibodies against erythrocytic recombinant antigens of P. vivax, Apical membrane antigen 1 (PvAMA-1), Erythrocyte binding protein 2 (PvEBP-2) and domain II of Duffy binding protein (PvDBPII) were also evaluated. Parameters, such as age, sex, PCR positivity, and captivity, potentially associated with humoral immune response were analyzed. Eighty-five percent of NP had antibodies against at least one CSP peptide, and 76% against at least one P. vivax erythrocytic antigen. A high percentage of adults compared to non-adults were seropositive and showed increased antibody levels. Neotropical primates with PCR positive for P. simium had a significantly higher frequency of positivity rate for immune response against PvEBP-2, PvDBPII and also higher antibody levels against PvDBPII, compared to PCR negative NPs for this species. Monkeys with PCR positive for P. brasilianum/P. malariae showed higher frequency of seropositivity and antibody levels against Pb/PmCSP. Levels of antibodies against Pb/PmCSP, PvEBP-2 and PvDBPII were higher in free-living than in captive monkeys from the same area. All Platyrrhine families showed antibodies against CSP peptides, however not all showed IgG against erythrocytic antigens. These findings showed a high prevalence of naturally acquired antibodies against CSP repeats in all studied areas, suggesting an intense exposure to infected-mosquitoes bites of NP from all families. However, mainly monkeys of Atelidae family showed antibodies against P. vivax erythrocytic antigens, suggesting blood infection, which might serve as potential reservoirs of malaria in the Atlantic Forest.

Lactobacillus nasalidis sp. nov., isolated from the forestomach of a captive proboscis monkey (Nasalis larvatus).

Three strains (YZ01T, YZ02 and YZ03) of Gram-stain-positive, facultatively anaerobic rods were isolated from the forestomach contents collected from a captive male proboscis monkey (Nasalis larvatus) at Yokohama Zoo in Japan. Phylogenetic analysis of the 16S rRNA gene sequences revealed that these strains belonged to the genus Lactobacillus. Based on the sequence similarity of the 16S rRNA gene, Lactobacillus delbrueckii subsp. indicus JCM 15610T was the closest phylogenetic neighbour to YZ01T. Sequence analyses of two partial concatenated housekeeping genes, the RNA polymerase alpha subunit (rpoA) and phenylalanyl-tRNA synthase alpha subunit (pheS) also indicated that the novel strains belonged to the genus Lactobacillus. The average nucleotide identity and digital DNA-DNA hybridization (dDDH) between L. delbrueckii subsp. indicus and YZ01T were 85.9 and 31.4 %, respectively. The phylogenetic tree based on the whole genomic data of strains YZ01T, YZ02 and YZ03 suggested that these three strains formed a single monophyletic cluster in the genus Lactobacillus, indicating that it belonged to a new species. The DNA G+C content of strain YZ01T was 51.6 mol%. The major fatty acids were C16 : 0 and C18 : 1 ω9c. Therefore, based on phylogenetic, phenotypic and physiological evidence, strains YZ01T, YZ02 and YZ03 represent a novel species of the genus Lactobacillus, for which the name Lactobacillus nasalidis sp. nov. is proposed with the type strain YZ01T (=JCM 33769T=DSM 110539T).

Aging-related Alzheimer's disease-like neuropathology and functional decline in captive vervet monkeys (Chlorocebus aethiops sabaeus).

Age-related neurodegeneration characteristic of late-onset Alzheimer's disease (LOAD) begins in middle age, well before symptoms. Translational models to identify modifiable risk factors are needed to understand etiology and identify therapeutic targets. Here, we outline the evidence supporting the vervet monkey (Chlorocebus aethiops sabaeus) as a model of aging-related AD-like neuropathology and associated phenotypes including cognitive function, physical function, glucose handling, intestinal physiology, and CSF, blood, and neuroimaging biomarkers. This review provides the most comprehensive multisystem description of aging in vervets to date. This review synthesizes a large body of evidence that suggests that aging vervets exhibit a coordinated suite of traits consistent with early AD and provide a powerful, naturally occurring model for LOAD. Notably, relationships are identified between AD-like neuropathology and modifiable risk factors. Gaps in knowledge and key limitations are provided to shape future studies to illuminate mechanisms underlying divergent neurocognitive aging trajectories and to develop interventions that increase resilience to aging-associated chronic disease, particularly, LOAD.

Monitoring the variation in the gut microbiota of captive woolly monkeys related to changes in diet during a reintroduction process

Microbiome is known to play an important role in the health of organisms and different factors such as diet have been associated with modifications in microbial communities. Differences in the microbiota composition of wild and captive animals has been evaluated; however, variation during a reintroduction process in primates has never been reported. Our aim was to identify changes in the bacterial composition of three individuals of reintroduced woolly monkeys (Lagothrix lagothricha) and the variables associated with such changes. Fecal samples were collected and the V4 region of the 16S rRNA gene was sequenced to determine gut microbial composition and functionality. Individual samples from released individuals showed a higher microbial diversity after being released compared to before liberation, associated with changes in their diet. Beta diversity and functionality analysis showed separation of samples from released and captive conditions and the major factor of variation was the moment of liberation. This study shows that intestinal microbiota varies depending on site conditions and is mainly associated with diet diversity. The intake of food from wild origin by released primates may promote a positive effect on gut microbiota, improving health, and potentially increasing success in reintroduction processes.

Male-Directed Object Use by Proceptive Female Bearded Capuchin Monkeys (Sapajus libidinosus) in Captivity

Some nonhuman primates use tools to modify the behavior of other animals in social contexts. For example, during their proceptive periods, female bearded capuchins (Sapajus libidinosus) in two wild groups throw stones and push branches toward males, which may function to draw male attention to the females. To further clarify the social and communicative relevance of this behavior, we recorded all occurrences of object use in a captive group (one adult male and four females) at Brasilia Zoo, during 963 h of observation. Additionally, we recorded the occurrence of typical proceptive behaviors and quantified behavioral changes of the male associated with throwing behavior. All females threw objects, such as stones and sticks, at the male (N = 205 events). One of the females also pounded objects near the male (N = 72). The two forms of object use were associated with female proceptivity. Male-directed throws increased the chances of the male changing his behavior, particularly by shifting his attention to the thrower, supporting the hypothesis that throwing at the male function as a communicative act. However, females also used aimed throwing in affiliative contexts (N = 2) and interactions with humans (N = 102) and other animals (N = 61). Thus, our results show that aimed throwing is a flexible behavior, elicited in multiple social contexts and for different purposes. Moreover, our study demonstrates that considering the effects of object use on the behavior of potential targets can help us to understand how primates use objects to mediate communication.

Effects of two dietary fiber levels on nutrient digestibility and intestinal fermentation products in captive brown howler monkeys (Alouatta guariba).

Herbivorous primates present a selective consumption profile and morphological adaptations to use the fibrous fraction of their diets. Brown howler monkeys (Alouatta guariba) are generalist herbivores; however, when kept under human care, they usually receive diets rich in fruits and with insufficient amounts of fiber. Thus, the objective of this study was to evaluate the effects of two levels of neutral detergent fiber (NDF) in howlers on apparent total tract digestibility coefficients (ATTDC), fecal consistency, and intestinal fermentation products. A group of 26 adult howler monkeys, 13 males and 13 females, were fed two diets formulated to have 33% or 40% NDF for 11 days, according to a randomized block design (N = 26). The block factor was the enclosures with one, two, or three individuals (each enclosure corresponded to an experimental unit), totaling in eight replicates per treatment. There were no differences in dry matter and nutrients intake between treatments (p > 0.05). The diet with 33% NDF resulted in higher (p < 0.05) ATTDC of crude proteinand crude energy. However, lower fecal concentrations of short-chain fatty acids (SCFA) and dry matter were observed in the treatment with 33% NDF in contrast to the 40% NDF group (p < 0.05). We recommend the inclusion of higher fiber levels (40% NDF) in the diet of howler monkeys since there is evidence of greater production of SCFA and improvement in fecal consistency.

Biochemistry, Doppler echocardiography, and electrocardiography evaluation in captive owl monkeys (Aotus sp).

The cardiovascular system of owl monkeys has been studied due to frequent postmortem findings of heart disease in asymptomatic animals. The silent aspect and the difficulty of early diagnosis intensify the importance of studying the cardiovascular system in this species. Echocardiogram evaluation was carried out on 60 animals, grouped into suspect or non-suspect of having heart diseases, and evaluated through electrocardiogram, hematology, and biochemical tests. Doppler echocardiography indicated two animals with suspicion of left ventricular hypertrophy and eight with dilated cardiomyopathy. Suspect animals had higher cardiac measurements and reduced shortening fraction. Troponin I was detectable in two animals (0.128ng/mL and 0.584ng/mL), and serum albumin concentration was significantly higher in non-suspect animals (P<.05). The importance of echocardiographic measurements of IVSd, IVSs, LVIDd, LVIDs, LVPWd, LVPWs, LA, EF, and FS in the cardiac evaluation of captive owl monkeys was evidenced.

Titi monkey neophobia and visual abilities allow for fast responses to novel stimuli

The Snake Detection Theory implicates constricting snakes in the origin of primates, and venomous snakes for differences between catarrhine and platyrrhine primate visual systems. Although many studies using different methods have found very rapid snake detection in catarrhines, including humans, to date no studies have examined how quickly platyrrhine primates can detect snakes. We therefore tested in captive coppery titi monkeys (Plecturocebus cupreus) the latency to detect a small portion of visible snake skin. Because titi monkeys are neophobic, we designed a crossover experiment to compare their latency to look and their duration of looking at a snake skin and synthetic feather of two lengths (2.5 cm and uncovered). To test our predictions that the latency to look would be shorter and the duration of looking would be longer for the snake skin, we used survival/event time models for latency to look and negative binomial mixed models for duration of looking. While titi monkeys looked more quickly and for longer at both the snake skin and feather compared to a control, they also looked more quickly and for longer at larger compared to smaller stimuli. This suggests titi monkeys’ neophobia may augment their visual abilities to help them avoid dangerous stimuli.

Monkeys fight more in polluted air

Air pollution is a global environmental problem, and its effects on human behavior, psychology, and health have been well studied. However, very few studies were done on if and how air pollution affects animal behavior, for example, social conflict. Many physiological and psychological evidences suggest a possible positive relationship between air pollution and animal social conflict, thus we established a multiple linear regression model using a captive monkey group to explore if monkeys behave more aggressively in polluted air. Our results confirmed that daily social fighting behaviors occurred more when air is polluted. Temperature has a nonlinear effect on monkey social conflict, with a fighting peak at 25–29 °C. To our knowledge, this is the first report that animal social conflict, like humans, is also affected by air pollution and temperature.

Analysis of fecal nutrients and particle size in captive proboscis monkeys (Nasalis larvatus) fed seasonal dietary foliage at a Japanese zoo.

One male and three female captive proboscis monkeys (Nasalis larvatus) were used as test animals to compare fecal nutrients after being fed seasonal foliage. Foliage and fecal samples were collected during three seasons (spring, summer, and winter). We analyzed crude ash (CA), ether extract (EE), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent lignin (ADL). In addition to the above components, for the fecal samples, we examined total fecal nitrogen (TFN), nitrogen in fecal NDF (NDF-N), metabolic fecal nitrogen (MFN), and particle size distribution (MPS). Seasonal differences in foliage components were observed, with NDF and ADF being lowest in spring (p < 0.05). Fecal NDF and ADF also tended to be lowest in spring. Further, the distribution of fecal particle size indicated that MPS tended to increase in winter. The mean fecal NDF content (47.4%) for all three seasons measured in this study was as much as 1.3 times lower than previously reported values in free-ranging specimens. These data provide useful information that can be used to find some suitable food items for the endangered highly folivorous monkeys in captivity.

Environmental factors associated With Toxoplasma gondii Exposure in Neotropical Primates of Costa Rica.

The apicomplexan parasite Toxoplasma gondii (T. gondii) has been found in more than 350 species of homoeothermic vertebrates in diverse climates and geographic areas. In most animals, T. gondii produces mild or asymptomatic infection. However, acute and hyperacute toxoplasmosis is associated with high mortality rates observed in Neotropical primates (NP) in captivity. These primates are distributed in 20 countries across the Americas, and although infection has been reported in certain countries and species, toxoplasmosis in the wild and its impact on NP population survival is unknown. Differences among species in exposure rates and disease susceptibility may be due in part to differences in host behavior and ecology. Four species of NP are found in Costa Rica, i.e., howler (Alouatta palliata), spider (Ateles geoffroyi), capuchin (Cebus imitator), and squirrel monkeys (Saimiri oerstedii). This study reports NP exposure to T. gondii using the modified agglutination test in 245 serum samples of NP (198 wild and 47 from captivity) from Costa Rica. Associations of serostatus with environmental (forest cover, annual mean temperature), anthropogenic (human population density), and biological (sex) variables in howler and capuchin monkeys were evaluated. The seroprevalence among wild NP was 11.6% (95% CI = 7.7–17.34), compared with 60% in captive monkeys (95% CI = 44.27–73.63), with significant differences between species (X2 = 20.072; df = 3, p = 0.000164), suggesting an effect of behavior and ecology. In general, antibody titers were low for wild NP (<1:128) and high for captive NP (>1:8192), suggesting higher exposure due to management factors and increased life span in captivity. Seropositivity in howler monkeys was positively related to forest cover and inversely related to annual rainfall. For capuchins, annual rainfall was inversely related to seropositivity. Surveillance of T. gondii exposure in NP in captivity and in the wild is required to understand drivers of the infection and develop novel strategies to protect them.

Use of Introduction Enclosures to Integrate Multimale Cohorts into Groups of Female Rhesus Macaques (Macaca mulatta).

Integrating animals into a new group is a challenge for both free-ranging and captive adult male rhesus monkeys (Macaca mulatta), and for females in groups receiving new males. To ensure the genetic viability of the population, however, male transfers must occur in both natural and captive settings. To facilitate the introduction of groups of adult males to adult females, we designed a new enclosure that is attached to the outdoor compound where females are housed. Here we describe the construction of 3 introduction enclosures, their use during 4 introductions of groups of adult males to adult females, a brief comparison of introduction success rates associated with the new introduction enclosures with those of our traditional male introduction method, and a critique by the various groups of staff members working with the new enclosures. Overall, the introduction enclosures benefitted both the macaques and the facility personnel and appear to be a useful enhancement to our process of integrating breeding groups.

Humeral fracture repair in an African green monkey (Chlorocebus sabaeus)

An approximately 16‐year‐old, 6.5‐kg entire male African green monkey (Chlorocebus sabaeus) was evaluated for acute‐onset soft‐tissue swelling and disuse of the left forelimb. Orthogonal radiographs of the humerus revealed a closed, complete, short oblique fracture of the distal one‐third humeral diaphysis. Open reduction and internal fixation (ORIF) was performed using a plate‐rod construct. Convalescence and proactive rehabilitation allowed for uneventful healing, with radiographic documentation of a bony union at the fracture site nine weeks postoperatively. Open fracture management in non‐human primates is uncommonly performed, and this case revealed some of the considerations and methods critical to ORIF of humeral fractures in captive monkeys.