Correlates of Male Consortship Rate in Free-Ranging Rhesus Macaques (Macaca mulatta)

Male–male competition for access to receptive females can take the form of nonrecurring fights and/or a sustained contest over mating opportunities. Male physical condition has been linked to dominance rank and reproductive success in species characterized by intrasexual fights for dominance and access to females. In group-living species characterized by endurance rivalry, however, factors contributing to male reproductive success are less well understood. In such species, particularly seasonally breeding ones with low sexual dimorphism and seniority-based rank, age and social factors other than rank may prove important. In the absence of genetic data, male mate guarding or consortship can serve as an indicator of male reproductive success. To evaluate the contribution of age and intragroup sociality to male consortship rate, I collected behavioral data during one nonmating and one mating season in two social groups of free-ranging rhesus macaques that experience no predation or food scarcity. Higher-ranking males, younger males, or males that exhibited lower rate of intrasexual aggression had higher consortship rates. Male–female dyads that groomed outside consortship did not form consortships as often as dyads that did not engage in nonconsort grooming. This is the first study to identify the significance of male–male aggression and male–female affiliation to male consortship rate in a species characterized by endurance rivalry, high male rank stability, and strong female mate choice. Social behaviors and male age may be particularly important in determining male reproductive success in populations experiencing high food availability and a lack of predation, which are typical of an increasing number of vertebrates in areas densely populated by humans.     

Extraintestinal Campylobacteriosis in Rhesus Macaques (Macaca mulatta)

Two cases of clinical disease associated with extraintestinal Campylobacter infection were recently encountered in rhesus macaques (Macaca mulatta). The first case was that of a 3-y-old, male, rhesus macaque experimentally infected with SIV, who presented with abdominal pain and a midabdominal mass and was euthanized. Pathology findings included an abscess within the median liver lobe, fibrinopurulent peritonitis, and intestinal serositis with isolation of Campylobacter fetus from the blood, liver, and the hepatic abscess. The second case was that of a 1-mo-old, female, rhesus macaque who died with no apparent history of illness. Gross pathology findings included thin body condition and diarrheic staining of the perineum; histologically, acute multifocal hepatitis with intralesional bacteria was noted. Campylobacter coli was isolated from the liver and colon. Extraintestinal Campylobacter infection is uncommon in humans, usually occurring in immunocompromised subjects and most commonly manifesting as bacteremia. Extraintestinal Campylobacter infections in animals are rare but have been associated with bacteremia and cholecystitis. The macaques presented here were either immunocompromised due to SIV infection (case 1) or more vulnerable due to young age (case 2). These factors likely contributed to the extraintestinal spread of Campylobacter.Campylobacter spp. are curved or spiral, gram-negative, microaerobic, typically motile bacteria with a single flagellum at one or both ends of the cell.²⁵ Campylobacter is one of the most common bacterial causes of gastroenteritis in humans worldwide.³ The Centers for Disease Control and Prevention estimate it to affect more than 1.3 million people in the United States each year.¹¹ Campylobacter spp. colonize the intestinal tract of primates, other mammals, birds, reptiles, and shellfish, but infection is not always associated with clinical signs of disease.^2,23 Contaminated or undercooked poultry represents the largest potential source of human infection.²² Campylobacteriosis is a zoonosis, and other significant sources of human infection include livestock, wildlife, pets, and contaminated water.²² The species most commonly isolated from humans and nonhuman primates are C. jejuni and C. coli; other species like C. fetus are less commonly found.^2,4,9,23 Extraintestinal campylobacteriosis in humans usually occurs in immunocompromised or elderly persons with underlying medical problems and most commonly manifests as bacteremia.²³ There have been a few reports of extraintestinal Campylobacter infections in animals, including bacteremia and cholecystitis in 2 dogs.^17,30     

Maternal Anxiety in Rhesus Macaques (Macaca mulatta)

Visual monitoring and scratching were used as behavioral indicators of maternal and social anxiety in small captive groups of rhesus macaques. Young infants were especially at risk from other group members during the first weeks of locomotion away from their mothers. Mothers received aggression from other individuals irrespective of their infants' presence or absence. The rate at which mothers scratched themselves increased significantly when their infants moved away from them and when the infants approached or were approached by individuals who frequently harassed them. The rate of maternal scratching and the rate of glancing at the infant and at other individuals when the infant was away decreased as infants grew older and became less vulnerable to harassment. In contrast, the rate of maternal scratching and visual monitoring of other individuals when the infant was in contact remained stable across the first 12 wk of lactation. The rate of maternal scratching increased when the mother-infant pair was in spatial proximity to the adult male or higher ranking adult females. Although visual monitoring and scratching showed a similar sensitivity to social variables, it is speculated that they might reflect different components of anxiety, namely, anticipation of danger and uncertainty due to motivational conflict. The results of this investigation indicate that a macaque mother's emotional reactivity to a perceived danger for herself and her infant can be measured quite accurately using the rates of visual monitoring and scratching and that the latter represent reliable tools to investigate the emotional correlates of maternal behavior in nonhuman primates.     

The Costs of Reproductive Success in Male Rhesus Macaques (Macaca mulatta) on Cayo Santiago

Sexual selection acts to increase the success of males possessing advantageous traits in competition over females. In primates, interspecific variability in social and mating systems creates highly variable selective pressures on males, changing the relative strength of both intra- and intersexual selection, and the relative degree of direct vs. indirect male–male competition. Rhesus macaques are an interesting species for studying intrasexual selection and male–male competition, because they exhibit relatively low (for Papionini) body and canine size dimorphism, and exhibit large testes, suggesting reduced direct competition and strong indirect competition. We have undertaken several studies of male rhesus macaques on Cayo Santiago, from analyses of long-term life-history data to shorter term projects that combined noninvasive measures of physiological markers such as concentrations of urinary C-peptide of insulin and androgen and glucocorticoid (GC) concentrations, with measures of behavior and of sexually selected signals (male red facial coloration). We here review these studies, combining data from short-term studies with long-term mortality data to present an integrated picture of both the short- and long-term gross costs of male mating competition. We find that males exhibit many signs of the costs of indirect competition, such as energetic consequences of reduced feeding and high copulation rates. During periods of more direct contest, such as during dominance instability, males are also characterized by high androgen and GC concentrations among high-ranking individuals. Consistent with relatively weak direct male–male competition, male red skin coloration appears to be more related to female choice (intersexual selection) than the signaling of dominance status (intrasexual selection). Forty-five years of life-history data show that male mortality is higher during the mating than the birth season, a pattern we hypothesize to be linked to the costs associated with mating activity. We finish by discussing unresolved issues, such as the costs of sperm competition and the data that are needed to address them.     

The Influence of Kinship on Familiar Natal Migrant Rhesus Macaques (Macaca mulatta)

In most primate species, females remain in the natal group with kin while males disperse away from kin around the time of puberty. Philopatric females bias their social behavior toward familiar maternal and paternal kin in several species, but little is known about kin bias in the dispersing sex. Male dispersal is likely to be costly because males encounter an increased risk of predation and death, which might be reduced by dispersing together with kin and/or familiar males (individuals that were born and grew up in same natal group) or into a group containing kin and/or familiar males. Here we studied the influence of kinship on familiar natal migrant rhesus macaques (Macaca mulatta) on Cayo Santiago, Puerto Rico, by combining demographic, behavioral, and genetic data. Our data suggest that kinship influences spatial proximity between recent natal immigrants and males familiar to them. Immigrants were significantly nearer to more closely related familiar males than to more distantly related individuals. Within a familiar subgroup, natal migrants were significantly closer to maternal kin, followed by paternal kin, then non-kin, and finally to males related via both the maternal and paternal line. Spatial proximity between natal immigrants and familiar males did not decrease over time in the new group, suggesting that there is no decline in associations between these individuals within the first months of immigration. Overall, our results might indicate that kinship is important for the dispersing sex, at least during natal dispersal when kin are still available.     

Stability and Durability of Intra- and Intersex Social Bonds of Captive Rhesus Macaques (Macaca mulatta)

Many social species maintain differentiated relationships with their group members. These social bonds may reflect short-term interactions satisfying immediate needs. Alternatively, individuals of some species may entertain stable and valuable bonds that last much longer than opportunistic interactions would predict. This claim is supported by recent research that revealed clear fitness benefits for long-lasting social bonds. Here, we investigated the stability and equitability of social relationships in captive rhesus macaques, measured using their proximity and grooming patterns over a 3-yr period. We show that, in general, proximity patterns of the whole group were stable over 3 yr. More specifically, each individual’s top two nonkin within and between sex relationships based on proximity were relatively stable and some of these relationships lasted the full 3 yr. Female grooming relationships within and between sex were also stable over 3 yr. Moreover, strong social bonds in females were not based on age similarity and were not sex specific, suggesting that a general underlying mechanism of social bonding in female rhesus macaques. In contrast, patterns of male grooming of other males and of females were relatively unstable and male social bonds were less equitable than those of females. The differences in stability of the relationships between the sexes may reflect the dispersal pattern of rhesus macaques, although we have limited data on non-natal males in our study. With these data we add to a growing body of literature describing the value and durability of relationships among primates and other species.     

Sneaky Monkeys: An Audience Effect of Male Rhesus Macaques (Macaca mulatta) on Sexual Behavior

Males and females have different sexual interests and subsequently may show conflicting sexual strategies. While dominant males try to monopolize females, promiscuity benefits females and subordinate males. One way to escape monopolization by dominant males is to copulate in their absence. We tested this inhibitory effect of males on the sexual behavior of their group members in captive group‐living Rhesus macaques. Copulations between females and nonalpha males almost exclusively took place when the alpha male was out of sight. Furthermore, the inhibiting effect was not unique for the alpha male. An upcoming nonalpha male also inhibited copulations of its group members, and three other nonalpha males inhibited female copulation solicitations. Females adjusted their behavior to the presence of bystander males, as they initiated and accepted initiations more often in absence than in presence of bystander males. Although not significant, in males, a similar pattern was found. The observed reduction in mating behavior in presence of bystander males is in accordance with an “audience effect,” in which the behavior is modulated in relation to the presence or absence of third parties. This audience effect may serve as an important mechanism to reduce (aggressive) interruptions of subordinate male copulations.     

Endometrial Decidualization and Deciduosis in Aged Rhesus Macaques (Macaca mulatta)

Superficial decidualization of the endometrial stroma is an essential feature of the implantation stage of pregnancy in rhesus macaques and other primates. Decidualization involves proliferation of the endometrial stromal cells, with differentiation into morphologically distinct decidual cells. Previous reports involving nonpregnant rhesus monkeys have described localized and widespread endometrial decidualization in response to administration of progesterone and synthetic progestogens. Ectopic decidua or ‘deciduosis’ describes the condition in which groups of decidual cells are located outside of the endometrium, most often in the ovaries, uterus and cervix but also in various other organs. In humans, most cases of deciduosis are associated with normal pregnancy, and ectopic decidua can be found in the ovary in nearly all term pregnancies. Here we describe pronounced endometrial decidualization in 2 rhesus macaques. Both macaques had been treated long-term with medroxyprogesterone acetate for presumed endometriosis, which was confirmed in one of the macaques at postmortem examination. In one animal, florid extrauterine and peritoneal serosal decidualization was admixed multifocally with carcinomatosis from a primary colonic adenocarcinoma. Cells constituting endometrial and serosal decidualization reactions were immunopositive for the stromal markers CD10, collagen IV, smooth muscle actin, and vimentin and immunonegative for cytokeratin. In contrast, carcinomatous foci were cytokeratin-positive. To our knowledge, this report describes the first cases of serosal peritoneal decidualization in rhesus macaques. The concurrent presentation of serosal peritoneal decidualization with carcinomatosis is unique.Abbreviations: GnRH, gonadotropin-releasing hormone; PAS, periodic acid–Schiff; SMA, smooth-muscle actinSuperficial decidualization of the endometrial stroma is an essential feature of the implantation stage of pregnancy in rhesus macaques and other primates.^13,27,29,37 This process typically begins, and is most prominent, adjacent to the spiral arteries, eventually expanding to affect the endometrium uniformly.³⁵ The endometrial stroma surrounds and supports the endometrial glands and is composed mainly of endometrial stromal cells and blood vessels.³⁵ Decidualization involves proliferation of the endometrial stromal cells, with differentiation into morphologically distinct decidual cells.^7,27,38 Endometrial stromal cells transform into large, polyhedral, cytoplasm-rich cells with large amounts of stored glycogen and are often binucleated or polyploid in character.^{6,13,27,30,35} Ultrastructurally, decidualized cells have numerous ribosomes, prominent rough endoplasmic reticulum and Golgi complexes, and cytoplasmic accumulation of glycogen and lipid droplets.^13,35 Consistent with their stromal origin, decidualized cells express mesenchymal immunohistochemical markers, such as vimentin, desmin, and muscle-specific actin.^{6,7,14,16,20,22}Initiation of decidualization by attachment of the blastocyst to the uterine epithelium depends on previous sensitization by progesterone secretion, after a brief priming by estrogen.^12,13,27 Estrogen and progesterone regulate a series of complex interactions at the interface between the developing embryo and the cells in the stromal compartment, leading to the formation of a differentiated maternal tissue (decidua) that supports embryo growth and maintains early pregnancy.²⁷ Postovulatory levels of circulating progesterone increase and help maintain the differentiation of decidual cells.^{7,13,33,37,38}Ectopic decidua or ‘deciduosis’ describes the condition in which groups of decidual cells reside outside of the endometrium, most often in the ovaries, uterus, and cervix; the fallopian tubes, peritoneum, omentum, diaphragm, liver, skin, spleen, appendix, abdominal–pelvic lymph nodes, renal pelvis, and lungs of women have also been reported as affected.^{6,14,18,20,22,28,29,38} In humans, most cases of deciduosis are associated with normal pregnancy, and ectopic decidua have been reported in the ovary in 90.5% to 100% of term pregnancies.^{6-8,14,20,22,28-30,38} Occasional cases in nonpregnant or postmenopausal women have been attributed to progesterone-secreting active corpora lutea, progesterone secretion by the adrenal cortex, trophoblastic disease, exogenous progestational agents, and pelvic irradiation.^{6-8,14,18,20,22,28,38} Deciduosis is usually an incidental finding that regresses postpartum within 4 to 6 wk; rarely, florid reactions have been reported to cause peritonitis, adhesions, hydronephrosis and hematuria, acute bowel obstruction or perforation (or both), abdominal pain mimicking appendicitis, massive and occasionally fatal hemoperitoneum, vaginal bleeding, and pneumothorax.^{6,7,14,18,20,22,28,29,31}Previous reports involving nonpregnant rhesus macaques have described localized and widespread endometrial decidualization in response to the administration of progesterone, synthetic progestogens, or progesterone-releasing bioactive intrauterine devices and intravaginal rings and have referred to these changes as ‘pseudodecidualization’ to indicate the absence of pregnancy in these animals.^12,33,35,37 In macaques given low (but superphysiologic) levels of progestogens, decidual changes have been noted in localized regions (around spiral arteries and underneath superficial epithelium), whereas high doses of progesterone or synthetic progestagens can cause a more pronounced and extensive reaction.³⁵In cynomolgus macaques, extrauterine decidual cell plaques are rare histologic findings in the subcoelomic mesenchyme of the ovarian cortex.^8,30 Despite the frequency of the condition in women, deciduosis is postulated to be a rarely documented lesion in primates because it is most often observed in conjunction with pregnancy, and pregnant cynomolgus macaques are seldom used in toxicity studies.⁸ Here we describe the pronounced endometrial decidualization of 2 rhesus macaques, one of which also had florid extrauterine and peritoneal decidualization that was admixed multifocally with carcinomatosis. Both macaques had been treated long-term with medroxyprogesterone acetate for presumed endometriosis, which was confirmed in one of the macaques at postmortem examination. To our knowledge, this report describes the first cases of peritoneal decidualization in rhesus macaques as well as the concurrent occurrence of carcinomatosis, endometriosis and peritoneal decidualization in a macaque. The extensive intermixing of the cell populations presented a diagnostic challenge at pathologic examination, and accurate diagnosis was achieved only through the use of multiple immunohistochemical markers.     

Sex Ratio, Conflict Dynamics, and Wounding in Rhesus Macaques (Macaca mulatta)

Rhesus macaques, like many other primates, live in stable, multi-male multi-female groups in which adult females typically outnumber adult males. The number of males in multi-male/multi-female groups is most commonly discussed in terms of mate competition, where the sex ratio is a function of an adult male's ability to monopolize a group of females. However, the relationship between sex ratio and group stability is unclear because the presence of many males may either reduce stability by increasing mate competition or may improve stability if adult males are key conflict managers. We investigated the relationship between sex ratio, male intervention behavior, and trauma in seven groups of captive rhesus macaques. Our results show that high-ranking adult males intervene twice as frequently as adult females (P<0.0001) and are about twice as successful (P<0.0001). Furthermore, the type of adult males present in the group affects the relationship between intervention behavior and rate of traumas: males must be unrelated to the highest-ranking matrilines. Groups with a lower ratio of females per male unrelated to the alpha and beta matrilines had better intervention success (P<0.04) and fewer traumas requiring veterinary care (P=0.003). We conclude that conflict management behavior by adult males, particularly those unrelated to the highest-ranking matrilines, is the mechanism by which sex ratio influences the frequency of traumas, and thus group stability. We therefore suggest that monitoring and managing the sex ratio of captive primate groups is one of many measurements to predict group stability.     

Alternative Activation of Macrophages in Rhesus Macaques (Macaca mulatta) with Endometriosis

Endometriosis is one of the most frequently encountered gynecologic diseases and a common cause of chronic pelvic pain and infertility. The pathophysiology of this syndrome can best be described as the presence of ectopic endometrium and a pelvic inflammatory process with associated immune dysfunction and alteration in the peritoneal environment. Macrophages play an important role in the progression and propagation of endometriosis. Alternative macrophage activation occurs in rodents and women with endometriosis but had not been examined previously in nonhuman primates. This case–control study aimed to characterize macrophage polarization in the ectopic and eutopic endometrial tissue of nonhuman primates with and without endometriosis. In addition, circulating cytokines in endometriosis cases and normal controls were investigated in an effort to identify serum factors that contribute to or result from macrophage polarization. Endometriosis lesions demonstrated increased infiltration by macrophages polarized toward the M2 phenotype when compared with healthy control endometrium. No serum cytokine trends consistent with alternative macrophage activation were identified. However, serum transforming growth factor α was elevated in macaques with endometriosis compared with healthy controls. Findings indicated that the activation state of macrophages in endometriosis tissue in nonhuman primates is weighted toward the M2 phenotype. This important finding enables rhesus macaques to serve as an animal model to investigate the contribution of macrophage polarization to the pathophysiology of endometriosis.Abbreviations: HLA, human leukocyte antigen; Iba1, ionized calcium binding adaptor molecule 1; M1, classically activated macrophage; M2, alternatively activated macrophage; sCD40L, soluble cluster of differentiation 40 ligand; TGF, transforming growth factor; VEGF, vascular endothelial growth factorEndometriosis is a common cause of chronic pelvic pain and infertility and affects more than 5.5 million women in North America alone.⁴¹ Although endometriosis is one of the most frequently encountered gynecologic health problems among women of reproductive age, the pathophysiology of this disease remains elusive due to its complexity and multifactorial etiology. The presence of functional endometrial glands and stroma outside the uterine cavity defines endometriosis. Currently, the most widely accepted theory for the origin of ectopic endometrial tissue is a combined effect of retrograde menstruation and associated implantation of endometrial fragments at an ectopic site. Progression of endometriosis lesions is thought to then be supported by peritoneal factors that allow cell adhesion and growth.⁴⁴ Although endometriosis is not a neoplastic disease, it exhibits aggressive features such as cellular proliferation, invasion, and vascular proliferation.¹² Strong evidence indicates that endometriosis involves a pelvic inflammatory process, with immune dysfunction and alteration in the peritoneal environment.^13,27 Numerous studies have demonstrated marked increases in macrophage populations and activity in the peritoneum of endometriosis patients.^6,54,59 Although macrophages are integral to homeostasis of the peritoneal environment, during endometriosis they mediate inflammation and facilitate the establishment and maintenance of the disease.Macrophages can be classified into 2 main populations: classically activated macrophages (M1), whose activating stimuli include IFNγ and LPS, and alternatively activated macrophages (M2), whose activating stimuli includes IL4, IL13, IL10, and transforming growth factor (TGF) β.⁵⁵ These polar phenotypes are not expressed together, but the activation state of tissue macrophages can change over time. This phenotypic switch is possible because macrophages retain plasticity, resulting in macrophage polarization that is transient and reversible.⁴⁰ A key component in determining the phenotype of the differentially activated macrophage is their response to microenvironmental signals, and this response allows for expression of a spectrum ranging from the M1 to M2 extremes.⁵¹ M1- and M2-activated macrophages perform different functions by producing pro- or antiinflammatory factors. M1 macrophages have enhanced endocytic functions and an enhanced ability to kill intracellular pathogens; they also secrete large amounts of proinflammatory cytokines such as IL1α, IL6, IL12, and TNFα.⁷ In contrast, M2 macrophages are involved in resolution of inflammation and promotion of tissue repair, and they secrete antiinflammatory and immunosuppressive cytokines including IL10 and TGFβ.³² M2 cells also express proangiogenic factors, such as coagulation factor XIII and vascular endothelial growth factor (VEGF) and have been associated with a high degree of vascularization in vivo.¹ The pathogenesis of endometriosis is therefore a likely combination of inappropriate or sustained polarization, leading to tissue damage (increased M1 response) and immune dysfunction (increased M2 response) and allowing for persistence of ectopic endometrial tissue.The use of animal models in endometriosis research is crucial. Work done with rodents involves the study of induced disease.⁵³ Despite this caveat, rodent models have been the basis for important contributions. Global macrophage depletion in a rat model of endometriosis effectively inhibits the initiation and growth of endometriosis implants.¹⁵ Attenuation of endometriosis has recently also been demonstrated in a mouse model of endometriosis.⁴ In that study, systemic depletion of macrophages was associated with failure of endometrial lesion development and defective angiogenesis of established lesions. Further evaluation of specific roles of differentially activated macrophages in that study⁴ showed that adoptive transfer of alternatively activated macrophages (M2) was associated with enhanced endometriosis progression. Conversely, adoptive transfer of inflammatory macrophages (M1) was associated with abrogated progression. In addition to evaluating murine lesions, the authors of the cited study⁴ investigated markers for alternative macrophage activation in women with endometriosis and matched controls which revealed increased expression of CD163 and CD206 (2 markers of M2 polarized macrophages) in endometriosis lesions as compared with disease-free peritoneum. Although many studies have been published about the pivotal role of macrophages in the pathophysiology of endometriosis, only a few have dealt with activation of the M1 and M2 macrophage phenotypes.^4,57 Furthermore, few studies have examined tissue infiltration of macrophages in eutopic endometrium of human subjects with endometriosis.^6,23 An exhaustive literature search failed to identify studies that investigate the role of M1 and M2 macrophage populations in eutopic endometrium.The current study uses rhesus macaques, which have been studied extensively in reproductive medicine.⁵⁸ Because spontaneous development of the disease requires menstrual shedding, endometriosis occurs naturally only in some nonhuman primate species, making development of lesions more comparable to the establishment of disease in humans.¹⁴ Compared with rodents, the nonhuman primate model of endometriosis is advantageous due to a close recapitulation of human disease and physiology. Work characterizing M1 and M2 macrophage activation in a species with spontaneous disease development may reflect a closer immunologic characterization to humans. In the current study, macrophage populations were evaluated in archival tissue collected from rhesus macaques with a diagnosis of endometriosis as confirmed by histologic examination. To characterize the phenotype of endometrial tissue macrophages in ectopic endometriosis lesions and eutopic endometrium of both cases and controls, immunohistochemistry was used to quantify cells expressing M1- and M2-specific markers. We hypothesized that endometriosis lesions and eutopic endometrium of rhesus macaques would be associated with a polarized macrophage infiltration consisting of increased numbers of M2 macrophages. This increase in M2 response may cause reduced immune clearance of ectopic endometrial cells, facilitating their implantation and growth. Further we speculated that M2 polarization would be associated with increased serum cytokines including IL10 and VEGF and decreased production of IL6, IL12, and TNFα. The lack of findings that support our hypotheses may suggest that the micro- or peritoneal environment is more important for lesion development or that another component of the systemic milieu is the determining factor in the development of endometriosis.     

Hematology and Culture Assessment of Cranially Implanted Rhesus Macaques (Macaca mulatta)

The use of percutaneous cranial implants in rhesus macaques (Macaca mulatta) has long been a valuable tool for neuroscience research. However, when treating and assessing these animals, veterinarians are required to make assumptions about diagnostic results due to a lack of research into how these implants affect physiology. Microbial cultures of cranial implant sites show an abundance of colonizing bacteria, but whether these microbes affect animal health and wellbeing is poorly understood. In addition, microbial antibiotic resistance can present significant health concerns for both the animals and the researchers. To help elucidate the relationship between percutaneous cranial implants and blood parameters, complete blood cell counts and serum chemistry results were assessed on 57 nonhuman primates at our institution from September 2001 to March 2017. Generalized estimating equations were used to compare the results before and after an animal''s first implant surgery. This modelling showed that cranial implants were a significant predictor of alterations in the number of neutrophils, lymphocytes, and red blood cells, and in the concentration of hemoglobin, alkaline phosphatase, creatinine, calcium, phosphorus, total protein, albumin, and globulin. Anaerobic and aerobic bacterial cultures were performed to identify bacteria associated with cranial implants. Staphylococcus spp., Streptococcus spp., and Corynebacterium spp. comprised the majority of the aerobic bacterial isolates, while Fusobacterium spp., Peptostreptococcus spp. and Bacterioides fragilis comprised the majority of anaerobic bacterial isolates. Using a Pearson r correlation for statistical analysis, we assessed whether any of these bacterial isolates developed antibiotic resistances over time. Cefazolin, the most frequently used antibiotic in monkeys in this study, was the only antimicrobial out of 41 agents tested to which bacteria developed resistance over time. These results indicate that percutaneous implants are associated with a generalized inflammatory state, multiple bacterial species are present at the implant site, and these bacteria may contribute to the inflammatory response.

Neuroscience research often employs in vivo analysis of neuronal distribution, activity, and function, all of which require visualization and manipulation of the brain in living animals. To achieve this, cortical structures are accessed by the placement of percutaneous implants that are anchored to the skull and outfitted with transcranial ports. Studies of the auditory system,^72,78 visual cortex,^20,22,46,54 motor cortex,^23,44 perception,⁷⁰ and optogenetics^23,80 have all benefitted from the use of these implants in multiple laboratory species. However, few studies have investigated the effects of these implants on the general physiology of research animals.³²Due to human similarities in neuroanatomy, physiology, social behavior, and cognition, rhesus macaques (Macaca mulatta) have proven invaluable in translational studies of cortical structures. This species has long been the recipient of percutaneous cranial implants²⁹ and therefore, has been the subject of many refinements in their construction to improve research outcomes.^{3,11,40,43,60} Traditionally, these implants are constructed out of titanium or titanium alloy hardware that is anchored in place with acrylic or bone cement. Recording chambers provide access points through craniotomy sites where devices are implanted into deeper structures of the brain. Titanium alloys have been shown to provide a good bone/implant interface through the development of titanium oxides;^17,32,59 however, these implants may leach ions into surrounding tissues, with unknown health or research implications.³² Acrylics provide a moldable and easily repairable substrate, but have poor biocompatibility.^5,53 Their addition to implants increases exposed tissue surface area, creating ideal environments for infectious agents to thrive.^2,43Cranial implants can develop complications, including inflammation and infections at skin margins and the bone/implant interface.³² Multiple species of bacteria, including Staphylococcus spp., Corynebacterium spp., Enterococcus spp., and Providencia rettgeri, have been recovered from the chambers and skin edges of cranial implants in rhesus macaques.^10,43,88 These infections may be due to manipulation and contamination of implants by the animals themselves. Chronicity of infections is also likely due to the inability to apply therapeutic agents to deeper regions of tissue shielded by the implant. Chronic pathology is evident in deeper structures at the neural-implant interface.⁶⁷ For example, sustained glial responses and neural degeneration have been identified at sites where electrodes and arrays contact brain tissue.^12,74Chronic inflammation has well-established effects on hematologic values, such as red and white blood cell counts, platelet numbers, and total protein measurements. Few studies are currently available that link chronic percutaneous implants to changes in hematology in rhesus macaques, requiring clinicians to use established reference intervals of nonimplanted animals when analyzing bloodwork. This requires assumptions about effects of implants on overall health; these assumptions may or may not be correct, but are the necessary basis for assessments and therapies. In this study, systemic physiologic changes were identified in clinically healthy, implanted animals to provide a framework for analysis of complete blood cell counts (CBC) and serum chemistry (CHEM) values for clinicians working with rhesus macaques with percutaneous implants. We also assess bacterial cultures taken from these implants to identify common contaminants and their antibiotic resistance profiles. We hypothesize that clinically healthy rhesus macaques with percutaneous implants have significantly different hematology profiles than those without implants, despite a lack of clinical signs. By understanding how implants and associated bacteria affect routine blood test results, observed changes can be better characterized as normal or abnormal, so that veterinary care can be tailored as needed. This important step will allow improved care and welfare of animals used in neuroscience research.     

Coat Color Variation and Pigmentation Gene Expression in Rhesus Macaques (Macaca mulatta)

Light-dark coat color variation is a common aspect of color diversity within and across mammalian taxa. This variation in pelage brightness is associated with aspects of evolutionary ecology, particularly for primates, but little is known about the genetic mechanisms underlying light-dark differences in pelage pigmentation. Previous work, focusing particularly on macaques (Genus Macaca), has found no clear relationship between color variation and coding sequences of key pigmentation genes. This suggests that other loci and/or gene regulatory differences underlie this variation and raises the question of how patterns of gene expression differ in light verses dark hair follicles. Here, we examine relative expression levels of pigmentation genes in hair follicles from free-ranging rhesus macaques (Macaca mulatta) showing stark light-dark coat color variation. We quantified the brightness (reflectance) of plucked hair tufts using a spectrophotometer. We extracted RNA from the follicles and used quantitative RT-PCR to measure the relative amounts of gene product (mRNA) for seven candidate pigmentation genes (MITF, MC1R, MGRN1, ATRN, SLC24A5, TYRP1, and DCT). Expression values were normalized with the house-keeping gene ACTB. All candidate genes were expressed at similar levels in dark, intermediate, and light hair, and thus, light-dark variation in macaque coat color is unlikely to be due to differences in the expression of these key pigmentation genes. This study represents the first examination of gene expression and natural color variation in a non-human primate population. Our results indicate that even in a system, like pigmentation, where a candidate-gene approach is promising, identifying important intra-specific gene regulatory differences remains challenging.     

Effect of Mating Activity and Dominance Rank on Male Masturbation Among Free‐Ranging Male Rhesus Macaques

The adaptive function of male masturbation is still poorly understood, despite its high prevalence in humans and other animals. In non‐human primates, male masturbation is most frequent among anthropoid monkeys and apes living in multimale–multifemale groups with a promiscuous mating system. In these species, male masturbation may be a non‐functional by‐product of high sexual arousal or be adaptive by providing advantages in terms of sperm competition or by decreasing the risk of sexually transmitted infections. We investigated the possible functional significance of male masturbation using behavioral data collected on 21 free‐ranging male rhesus macaques (Macaca mulatta) at the peak of the mating season. We found some evidence that masturbation is linked to low mating opportunities: regardless of rank, males were most likely to be observed masturbating on days in which they were not observed mating, and lower‐ranking males mated less and tended to masturbate more frequently than higher‐ranking males. These results echo the findings obtained for two other species of macaques, but contrast those obtained in red colobus monkeys (Procolobus badius) and Cape ground squirrels (Xerus inauris). Interestingly, however, male masturbation events ended with ejaculation in only 15% of the observed masturbation time, suggesting that new hypotheses are needed to explain masturbation in this species. More studies are needed to establish whether male masturbation is adaptive and whether it serves similar or different functions in different sexually promiscuous species.     

Hormonal Correlates of Maternal Style in Captive Macaques (Macaca fuscata and M. mulatta)

Previous studies on nonhuman primate maternal styles showed that variation in infant-directed behavior falls along two dimensions, traditionally labeled as protectiveness and rejection. We investigated maternal styles in rhesus (Macaca mulatta) and Japanese (M. fuscata) macaques living in analogous captive social groups, and correlated them with the levels of estrogen metabolites excreted in female feces during the perinatal period. We focally observed mother-infant pairs 3 hours per week during the first 12 weeks of infant life. We collected fecal samples twice a week from each mother, starting 4 weeks before delivery and ending 4 weeks after delivery. Three significant components were extracted by principal component analysis from 15 different infant directed behaviors, each reflecting a different aspect of mothering style: rejection is correlated with behavioral measures of maternal opposition to contact; protectiveness is correlated with maternal solicitude; and independence is correlated with time in contact, grooming and cradling. Levels of estrogen metabolites are significantly correlated to rejection but not to protectiveness or independence, indicating that, in nonhuman primates, individual endocrine changes related to maternal behavior might specifically affect the timing of contact interruption.     

南京红山森林动物园猕猴的社会玩耍行为

社会玩耍行为是灵长类动物的常见行为类型之一,作为种群数量最大的非人灵长类之一,猕猴(Macaca mulatta)的社会玩耍行为是它们日常生活的一部分。本研究利用红外摄像技术,对南京红山森林动物园猕猴冬季社会玩耍行为的基本特征进行了研究。研究记录了每一回合玩耍行为的发生时间、持续时间、参与对象年龄、参与个体数以及玩耍行为类型等行为参数。在持续10 d的视频中,共记录到猕猴的社会玩耍行为7 496次,其中触摸和抓打4 018次,追逐1 012次,撕咬和摔跤671次,其他53次,以及各种玩耍行为组合1 742次。利用单因素方差分析,发现猕猴的社会玩耍行为节律明显,两个玩耍高峰分别为08:30~09:30时和10:30~11:30时。利用Kruskal-Wallis检验及Mann-Whitney U两两比较法,发现参与个体数和玩耍行为类型对社会玩耍持续时间影响显著,在玩耍过程中,参与个体数越多,社会玩耍持续时间越长;组合类型的持续时间最长,其次是撕咬和摔跤,再次是触摸和抓打,最后是追逐。0~3岁的少年个体在玩耍行为中更常采用触摸和抓打类型,而亚成年及成年个体则倾向于选择追逐类型。该研究量化了猕猴社会玩耍行为的类别和影响因素,为动物园的猕猴管理和动物福利提供了数据支持。