Hierarchical organization of rhesus macaque behavior

Primatologists, psychologists and neuroscientists have long hypothesized that primate behavior is highly structured. However, fully delineating that structure has been impossible due to the difficulties of precision behavioral tracking. Here we analyzed a dataset consisting of continuous measures of the 3D position of fifteen body landmarks from two male rhesus macaques (Macaca mulatta) performing three different tasks in a large unrestrained environment over many hours. Using an unsupervised embedding approach on the tracked joints, we identified commonly repeated pose patterns, which we call postures. We found that macaques' behavior is characterized by 49 distinct identifiable postures, lasting an average of 0.6 seconds each. We found evidence that behavior is hierarchically organized, in that transitions between poses tend to occur within larger modules, which correspond to intuitively identifiably actions; these actions are in turn organized hierarchically. Our behavioral decomposition allows us to identify universal (cross-individual and cross-task) and unique (specific to each individual and task) principles of behavior. These results demonstrate the hierarchical nature of primate behavior and provide a method for the automated "ethogramming" of primate behavior.

Nutrient digestibility of fishmeal rations in primates

The results of the study on effects of fishmeal on nutrient digestibility and intake in primates are given in the paper. Fishmeal is a feeding stuff, manufactured from fish, marine mammals, invertebrates not suitable for human consumption and by-products of their processing. Fishmeal nutrient composition includes natural substances and minerals, including phosphorus, calcium, iodine, selenium, several essential amino acids, as well as vitamins А, D and В complex. Fishmeal is known to be rich in digestible energy and proteins. One kilogram of fishmeal contains 700 grams of raw protein and up to 15 MJ of digestible energy. It should be noted that fishmeal is easily digested by animals. Nevertheless, there is a lack of data in publications on use of fishmeal as high protein feed in rations of primates. In this regard, the aim of the study was to analyze the effects of fishmeal on digestibility of mixed feed nutrients in male rhesus-macaques and to use the obtained results for understanding of prospects of fishmeal further use for feeding primates. The chemical composition and nutritional value of the total mixed ration was determined. The economic effectiveness of the fishmeal use in the rations of primates was calculated. Based on the experimental data, it was established that the inclusion of fishmeal (18% out of total) into the diet contributes to the improvement of feed intake in experimental primates and reduces the costs of complete granular feed.

Improved Training and Semen Collection Outcomes Using the Closed Box Chair for Macaques

Collaborative semen collection in monkeys is a valuable tool in research, animal collection management, and conservation efforts. To obtain samples, monkeys are often restrained in open restraint chairs (ORC) with the “pole and collar” technique. While commonly used, this restraint is not tolerated by all individuals; some become anxious or aggressive towards the poles and people. In an effort to refine this procedure and improve welfare of the monkeys, we examined the use of a “closed box chair” (CBC), a clear, plexiglass box in which the monkey is trained to sit for sperm collection. The CBC does not require pole and collar, and although legs are secured, the arms and neck are not restrained. The use of CBCs has increased in recent years; however, there are few studies demonstrating its effects on scientific outcomes. We used positive reinforcement techniques to train 34 adult male rhesus macaques (Macaca mulatta) to provide semen samples using either the ORC or the CBC. While all CBC monkeys (n = 14) were reliably trained for this procedure, only 75% of ORC (n = 20) males completed the training (p = 0.04). It took significantly less time to train animals in the CBC than the ORC (201.0 vs. 412.4 min; p <0.001). In a controlled subset, males restrained with ORC (n = 7) produced a significantly lower ejaculatory volume than those collected by CBC (n = 10) (297.6 µL vs 522.1 µL respectively; p = 0.04) and had a lower concentration of sperm (186.0 × 106/mL vs 367.5 × 106/mL respectively; p = 0.017), although there were no differences with respect to sperm motility (p = 0.15). Our data suggest the closed box chair technique reduces stress on the animals while enhancing semen quality, supporting the use of the CBC as an important refinement.

Environmental Effect of HV Towers at the Cerebellum and Cognitive Impairments in the Monkey

Today, living or working of people in the vicinity and even under the high-voltage lines is a pernicious environmental hazard to humans. The male rhesus monkey is used to investigate the effects of fields produced by high-voltage towers. In this study, the function and level of effect in rhesus monkeys' brain have been investigated in cerebellum's cognitive, biological and structural perspective. Two monkeys have been used, one as a control and the second under test. The monkey under test was subjected to a simulated HV electrical field of 3 kV/m for 4 hours a day for a one month. Behavioral tests were performed using a device designed and built for this purpose. Concentration analysis of adrenocorticotropic hormones (ACTH) and inspection of glucocorticoid receptor gene's (GR) expression were performed by the RT-PCR method. Changes in cerebellar anatomy with MRI images were examined. All tests were performed before and after the test period and were compared with the control monkey. Cognitive tests showed a significant reduction for the monkey that was exposed to a high-voltage electrical field in the first week after field imposition compared with the same time before. Also, the expression of the GR gene was decreased and the concentration of ACTH hormone in plasma was increased. Surveying the level of cerebral MRI images did not show any difference, but hemorrhage was evident in a part of the cerebellum. The results of cognitive, biological and MRI tests in the tested monkey showed a decrease in the visual learning and memory indices.

The Effect of 12 Hz Extremely Low-Frequency Electromagnetic Fields on Visual Memory of Male Macaque Monkeys

Introduction: Today, humans leave in a world surrounded by electromagnetic fields. Numerous studies have been carried out to discover the biological, physiological, and behavioral effects of electromagnetic fields on humans and animals. Given the biological similarities between monkeys and humans, the goal of the present research was to examine Visual Memory (VM), hormonal, genomic, and anatomic changes, and changes of the amygdala function in the male rhesus macaques who exposed to extremely low-frequency magnetic fields (ELF/MF). Materials and methods: Four male Rhesus Macaques (Macaca mulatta) were used. For the behavioral tests the animals were needed to be fasting for 17 hours, and for the behavioral tests such as visual memory, cooperation of the animal was necessary. Using the radiation protocol, two of the monkeys were exposed to 12-Hz electromagnetic fields with a magnitude of 0.7 microtesla (electromagnetic radiation) four hours a day for a month. Before and after the exposure, a visual memory test was conducted using a coated device (visible reward) on a movable stand. Ten mL of blood was obtained from the femoral artery of the monkeys and half of it was used to examine cortisol serum levels using MyBioSource kits (made in the USA). The other half of blood samples were used to extract lymphocytes for assaying expressions of Glucocorticoid Receptor (GR) genes before and after radiation using the PCR method. Anatomic studies of the amygdala were carried out based on pre- and post-radiation Magnetic Resonance Imaging (MRI). Findings: Research results indicated that visual memory in male primates increased significantly at the 12Hz frequency. Hormonal analysis at the 12Hz frequency showed a decrease in cortisol serum levels. However, visual memory and serum cortisol levels did not change considerably in male primates in the control group. There was no considerable amygdala volumetric difference at the 12 Hz frequency. The expression of the GR genes decreased at 12Hz compared to the control group. Conclusion: In short, these results indicated that ELF may have a beneficial value for memory enhancement as indicated by the fact that exposure to the 12 HZ ELF can enhance visual memory. This may be due to a decrease in plasma cortisol, and/or expression of GR genes. Moreover, direct involvement of the amygdala in this regard cannot be recommended.