Mineralized Trichobezoars in a Rhesus Macaque (Macaca mulatta).

A five-year-old female rhesus macaque (Macaca mulatta) presented with a thin body condition and multiple palpable mid-abdominal masses. Mineralized cecal trichobezoars were removed surgically. Thirteen months later, similar masses recurred and were confirmed with radiographs. This is the first case report of a mineralized cecal trichobezoar in a rhesus macaque.

Rhesus macaque personality, dominance, behavior, and health.

Previous studies of nonhuman primates have found relationships between health and individual differences in personality, behavior, and social status. However, despite knowing these factors are intercorrelated, many studies focus only on a single measure, for example, rank. Consequently, it is difficult to determine the degree to which these individual differences are independently associated with health. The present study sought to untangle the associations between health and these individual differences in rhesus macaques (Macaca mulatta). We studied 85 socially housed macaques at the Oregon and California National Primate Research Centers, and used veterinary records to determine the number of injuries and illnesses for each macaque. We measured personality using 12 items from a well-established primate personality questionnaire, performed focal observations of behaviors, and calculated dominance status from directional supplant data. All twelve personality questionnaire items were reliable and were used to represent five of the six personality dimensions identified in rhesus macaques-Dominance, Confidence, Openness, Anxiety, and Friendliness (also known as Sociability). Following this, we fit generalized linear mixed effects models to understand how these factors were associated with an animal's history of injury and history of illness. In the models, age was an offset, facility was a random effect, and the five personality dimensions, behavior, sex, and dominance status were fixed effects. Number of injuries and illnesses were each best represented by a negative binomial distribution. For the injury models, including the effects did improve model fit. This model revealed that more confident and more anxious macaques experienced fewer injuries. For the illness models, including the fixed effects did not significantly improve model fit over a model without the fixed effects. Future studies may seek to assess mechanisms underlying these associations.

Trauma rates and patterns in specific pathogen free (SPF) rhesus macaque (Macaca mulatta) groups.

There are some predictable patterns of trauma in captive rhesus macaque (Macaca mulatta) social groups. Several factors have been documented to contribute to these patterns, including group formation of unrelated animals, and the establishment of dominance ranks. Here, we report on how socially induced trauma in groups of rhesus monkeys is influenced by the breeding season, numbers of matrilines per group and matriline size. We analyzed 3 years of data collected from veterinary admittance logs for four groups in our specific pathogen free (SPF) breeding colony. Since the groups differed in time from formation, both the numbers of matrilines and the composition of those matrilines were different. Across the four groups, trauma rates were significantly higher during the fall breeding season than the spring and summer months when births occur. The group that was formed most recently, comprised of the greatest number of matrilines but fewest related animals, showed significantly higher rates of trauma than the older social groups. Further, the middle and lowest ranking families received signifincantly higher rates of trauma than the highest ranking families, suggesting a rank-related phenomenon. Additionally, there was a significant negative correlation between numbers of adult females in a matriline and rates of trauma observed in each matriline, but the numbers of adult females are significantly higher in the top ranked families compared to all of the other matrilines. These findings suggest that trauma rates increase during the breeding season and may be exacerbated in recently formed breeding groups that have smaller matrilines and reduced opportunities for social support to mitigate rank-related aggression. Management practices should be devised to ensure adequate matrilineal size to decrease rates of trauma in captive rhesus macaque groups.

Combination of kinematic analyses and diffusion tensor tractrography to evaluate the residual motor functions in spinal cord-hemisected monkeys.

BACKGROUND: Spinal cord injury (SCI) causes loss of locomotor functions. Nowadays, the relationship between the residual locomotion after SCI and the diffusion tensor tractography (DTT) results still remains unclear. METHODS: Four rhesus monkeys were suffered thoracic cord hemisection. Kinematic evaluation and DTT were performed prior- and post-SCI (6 and 12 weeks). The longitudinal changes of gait parameters and the DTT parameters were analyzed for the injury-contralateral hindlimb. The correlations between gaits and DTT parameters were also investigated. RESULTS: Almost gait parameters significantly changed after SCI, meanwhile, the caudal-rostral connection rate of DTT showed negative correlation with all gait parameters, demonstrating that the locomotor changes of the injury-contralateral hindlimb were associated with the ratio of residual fibers. CONCLUSIONS: The combinatory use of gait analysis and DTT has been demonstrated to be sensitive to locomotion changes after SCI, and may therefore have potential applications in the pre-clinical studies of SCI.

Reproductive consequences of a matrilineal overthrow in rhesus monkeys.

Matrilineal overthrows in macaque societies are rare but devastating events, often resulting in severe morbidity, mortality, and loss of individual and group fitness. The handful of documented macaque overthrows provides scant evidence to reveal the severity or longevity of reproductive consequences resulting from such violent events. We analyzed archival records from semi-free ranging rhesus monkeys, Macaca mulatta, across 6 years (55 ≤ N ≤ 107, from 2007 to 2012) during which time a matrilineal overthrow occurred (in 2009) to test the hypothesis that extremely violent interactions such as a matrilineal overthrow would significantly reduce reproductive fitness for the involved matrilines and for the troop collectively. The matrilineal overthrow resulted in a significant increase in infant loss for the population from the previous year (χ(2) = 8.117, df = 1, P = 0.004), as evidenced by the fact that in 2009, but not in other years, the proportion of infants lost was greater than the proportion of viable infants (χ(2) = 4.55, df = 1, P = 0.03). Moreover, the deposed matriline suffered 100% infant loss in 2009, a significant change from the previous year (χ(2) = 7.87, df = 1, P = 0.005) while the attacking matriline suffered 50% infant loss (also a significant change from the previous year; χ(2) = 4.44, df = 1, P = 0.035), with the uninvolved, lowest-ranking matriline showing no change in infant loss from the previous year (χ(2) = 0.008, df = 1, P = 0.93). The deposed matriline did not produce viable offspring again until 3 years later. We further found that rates of severe fighting (as indicated by the number of fight wounds requiring medical treatment) were positively correlated with infant loss across the 6 years of the study (r[s] = 0.943, P = 0.005). Our data indicate that extreme periods of intra-group conflict, such as the matrilineal overthrow, have marked short-term consequences for individual fitness, and may be extreme examples of the long-term influences that group violence exerts on the mean fitness within a primate troop.

Retrospective analysis of wound characteristics and tetanus development in captive macaques.

Traumatic wounds and access to outdoor enclosures containing soil contribute to development of tetanus in nonhuman primates. A retrospective, matched case-control study was conducted at a primate center to evaluate these factors by analysis of medical records of animals sustaining traumatic injuries during a 3-yr study period. Thirty-one macaques with traumatic injuries and a clinical diagnosis of tetanus were selected as cases, and 62 macaques with traumatic injuries and no diagnosis of tetanus were selected as controls. For an animal with injuries to the digits, the odds of developing tetanus were 9.6 times those of a similar animal without injuries to the digits (Odds Ratio [OR] = 9.55, 95% CI = 1.56-58.59); with injuries to the tail, the odds of developing tetanus were 8.0 times those of a similar animal without injuries to the tail (OR = 7.95, 95% CI = 0.82-77.04); and with injuries in more than one location, the odds of developing tetanus were 8.5 times those for a similar animal with injuries in just one location (OR = 8.45, 95% CI = 1.01-70.46). A nonhuman primate with injuries to the leg was less likely to develop tetanus than a similar nonhuman primate without injuries to the leg (OR = 0.19, 95% CI = 0.03-1.2). Results indicated that wound location is associated with development of tetanus infection in rhesus macaques. Identification of high-risk trauma cases will allow better allocation of wound management and tetanus prophylaxis in institutions, especially in those housing nonhuman primates outdoors.

Risk factors and remediation of self-injurious and self-abuse behavior in rhesus macaques.

Considered signs of decreased welfare--abnormal behaviors such as self-injury and self-abuse among nonhuman primates housed in the laboratory--may put into question the validity and reliability of scientific research using these animals as models. Providing environmental enrichment decreases the incidence of some undesirable behaviors but is often unsuccessful at ameliorating the most severe types of abnormal behaviors. To prevent such behaviors from developing, it is important to identify risk factors that provide insight into the causes of certain abnormal behaviors. This study confirmed previous research identifying nursery rearing, single housing, and time spent in single housing as important risk factors. Results also indicate that the number of cage relocations affects the development of these behaviors. In addition, this study presents new data on comorbidity of several abnormal behaviors and discusses possible reasons for these patterns.

The regional cortical basis of achromatopsia: a study on macaque monkeys and an achromatopsic patient.

Previous experiments have revealed total loss of colour vision following removal of all inferior temporal cortex, a condition akin to complete cerebral achromatopsia in humans. Whether less extensive ablation genuinely impairs colour perception without abolishing it or retards learning involving coloured stimuli is contested. We therefore tested macaque monkeys, with total removal of temporal areas TEO and TE but sparing rostral and perirhinal temporal cortex and the upper bank of the superior temporal sulcus. Compared with three monkeys with lateral parietal ablations, the monkeys with TEO/TE lesions were impaired at learning and retention of simultaneous two-choice colour discriminations and with a nine-choice oddity discrimination whether the coloured target was embedded among grey distracters of the same luminance or among isoluminant coloured distracters. However, their performance was superior to that of an achromatopsic human subject and to that previously measured in monkeys with much larger temporal lobe ablation. They were only mildly impaired at nine-choice oddity discrimination for grey stimuli where the grey target was brighter than the grey distracters. The impairment could be exacerbated or alleviated by altering the colour of the background of the displays and by static and dynamic luminance masking of the entire display in a manner that indicates that the colour deficit reflects a change in perception rather than a disorder of learning and memory. It resembles central dyschromatopsia in human subjects but falls short of achromatopsia.

Crowding stress and violent injuries among behaviorally inhibited rhesus macaques.

Environmental stressors and stable individual differences in human behavior have both been implicated etiologically in injuries. Because stress-related injuries are difficult to study experimentally in humans, the authors examined injury incidence in a troop of 21 male and 15 female free-ranging rhesus macaques (Macaca mulatta) before, during, and after a 6-month group confinement. Individual differences in behavioral inhibition to novelty were assessed, using multiple, quantified observations of behavior by 3 independent raters during 3 previous years. Incidence and severity of medically attended injuries were ascertained from veterinary records over a 2-year study period. A 5-fold increase in the incidence of injuries was documented during confinement stress, and an interaction was found between the stressor and behavioral inhibition in the prediction of injury incidence. Highly inhibited animals had significantly higher injury rates during confinement, compared with their uninhibited peers, but equal or lower rates in the low stress periods that preceded and followed confinement. Inhibited individuals appeared to have been specifically targeted for violence during the group stressor but were protected under normative, more predictable conditions.

Pair-housing rather than single-housing for laboratory rhesus macaques.

A total of 378 adult and juvenile rhesus macaques of both sexes were transferred from single- to isosexual pair-housing arrangements. The incidence of serious injury resulting from partner incompatibility was 0.8% during the first year after pair formation. It was concluded that pair-housing offers a safe option to address the animals' social needs in compliance with federal rules and professional standards.