Gestation length in rhesus macaques (Macaca mulatta)

We describe some of the sources of variation in gestation length among rhesus macaques. the data were obtained from the timed-mating breeding program at the California Regional Primate Research Center (CRPRC). Information about approximately 700 pregnancies that resulted in spontaneous vaginal deliveries of liveborn young is presented. The average length of these pregnancies was 166.5 days. In this population, older females with higher parities had significantly longer pregnancies and significantly heavier infants than other females did. Other factors, including infant sex, month of conception, maternal reproductive history, and paternal identity, had no consistent effect upon gestation length.     

High-resolution chromosomes of rhesus macaques (Macaca mulatta)

Late-prophase high-resolution chromosomes were successfully cultured for 22 of 27 Macaca mulatta samples. Twelve of the successful cultures were adequate for karyotyping high-resolution spreads. High-resolution chromosome technique provides an important contribution to primate genetics because it can be used to identify chromosomal anomalies undetected in metaphase spreads and may be useful for paternity exclusion analysis.     

Endocranial suture closure in rhesus macaques (Macaca mulatta)

Endocasts from skulls of 330 rhesus monkeys (Macaca mulatta) of known age are scored for closure of nine bilateral and three unilateral sutures or segments of sutures. A variety of tests reveals a strong relationship between age and stages of suture closure, although increasingly broad confidence intervals prevent sutures from being very useful for precisely aging older macaques. The order in which endosutures begin to close, as well as that in which closure is finally achieved, is determined for macaques, and these sequences compared to those for endosutures of humans (Todd and Lyon, 1924). The basilar suture is the earliest to close, while the masto-occipital and rostral and caudal squamosal sutures achieve closure quite late in both species. On the other hand, humans and macaques differ in their schedules for the sphenofrontal suture and in the initiation of closure for the rostral portion of the squamosal suture. Two sutures close significantly sooner on the right than on the left side (the rostral squamosal and masto-occipital) and asymmetry favoring closure of the right lateral lambdoid suture also approaches significance at the 0.05 level. No sutures close significantly sooner on the left side. It is suggested that macaque sutures may close from the inside out, that endosutures are more sensitive than ectosutures for detecting sequences in which cranial sutures begin to close, and that directional asymmetries in suture closure of macaques may be related to minor asymmetries in brain/skull shape (petalias).     

Systemic arteriopathy in SIV-infected rhesus macaques (Macaca mulatta)

BACKGROUND: Severe disseminated vasculopathy was observed in two simian immunodeficiency virus (SIV)-infected rhesus macaques (Macaca mulatta). These animals developed clinical signs of AIDS, including lymphadenopathy, weight loss, diarrhea and collapse. RESULTS AND DISCUSSION: Grossly, both animals showed emaciation, lymphadenopathy, vegetations on the mitral valve, renal infarcts and a dilated intestine; one animal had multifocal hemorrhages in multiple organs. Histologically, both cases had disseminated arteriopathy characterized by intimal thickening and fibrosis with varying degrees of vasculitis. The lesion was prominent in the kidney, intestine, pancreas, liver, heart, lymph nodes, spleen and testis. Occasional venules had intimal thickening. Both cases had cytomegalovirus (CMV) infection with intranuclear inclusions, CMV antigen and nucleic acid; some inclusions were observed in endothelial cells within some of the vascular lesions in one of the two. These data suggest that CMV caused the unusual lesions.     

Ecology of rhesus macaques (Macaca mulatta) in northwest Pakistan

The feeding ecology of rhesus monkeys,Macaca mulatta, was studied between 1978 and 1981. The study site, located in the Murree Hills of northwestern Pakistan, supported a mixed coniferous-deciduous forest community and was characterized by a high degree of human disturbance. We used a linear transect method to sample the species composition and structure of the vegetation. Comparison of these data with historical records showed that the forest has undergone major changes in the last hundred years. Data on feeding behavior were collected through on-the-minute focal animal sampling. The monkeys spent about 45% of the day feeding. Their preferred foods were grass, clover, and other ground herbs that occur in the disturbed sites. Fruit accounted for less than 9% of feeding records. The rhesus monkey may be pre-adapted to living in disturbed-site, forest-edge communities. The evolutionary history of Macaca mulatta may be tied closely to the disappearance of forest and the spread of meadows and savannahs over the last million years.     

Umbilical cord hypercoiling in two rhesus macaques (Macaca mulatta)

Obstruction of umbilical blood flow is a common cause of death in fetal nonhuman primates, but cord accidents have not been reported in the macaque. We describe two cases of cord accident in rhesus macaques (Macaca mulatta) resulting in fetal death at approximately 110 and 50 days of gestation, respectively.     

Multiple sirehood in free-ranging twin rhesus macaques (Macaca mulatta)

Rhesus macaque females regularly copulate with a number of partners, and produce a single offspring per reproductive cycle in over 99% of cases. We used genotyping of 10 STR markers to determine paternity in the Cayo Santiago population of rhesus macaques. About 1,500 monkeys have been analyzed to date, with their marker genotypes entered into a computerized database. These data enable us to report the first documented case in any cercopithecine nonhuman primate species of the production of twin offspring sired by different males.     

Consortships and conceptions in captive rhesus macaques (Macaca mulatta)

A captive group of rhesus macaques (Macaca mulatta) was observed during the breeding season to determine if consortship behavior, rather than promiscuous matings, resulted in higher reproductive success for either partner. The 38 adult females in this group were observed “in consort” with the 5 adult or 4 subadult males on 179 occasions. Most of these consortships were short-term, lasting less than one day. Six females engaged in consortships with one male that spanned more than three days, but the majority of these long-term associations did not result in a pregnancy with that male. The term “consortship” has been traditionally accepted as a specific nonhuman primate mating pattern, but the exact nature of this behavioral pattern and its evolutionary importance have been less clearly understood. Consort behavior could be considered a precursor to a monogamous mating system if long-term exclusive sexual associations resulted in higher reproductive success for the participants. But this study demonstrates that for rhesus macaques, who exhibit both consort behavior and more promiscuous matings, there is no clear reproductive advantage to long-term consortships. In light of the inconsistent use of the term consortship, the possible adaptive significance of an exclusive male-female sexual association for the evolution of human mating patterns needs to be reevaluated.     

Genetic characterization of rhesus macaques (Macaca mulatta) in Nepal

Indian-origin rhesus macaques (Macaca mulatta) have long served as an animal model for the study of human disease and behavior. Given the current shortage of Indian-origin rhesus, many researchers have turned to rhesus macaques from China as a substitute. However, a number of studies have identified marked genetic differences between the Chinese and Indian animals. We investigated the genetic characteristics of a third rhesus population, the rhesus macaques of Nepal. Twenty-one rhesus macaques at the Swoyambhu Temple in Kathmandu, Nepal, were compared with more than 300 Indian- and Chinese-origin rhesus macaques. The sequence analyses of two mitochondrial DNA (mtDNA) loci, from the HVS I and 12 S rRNA regions, showed that the Nepali animals were more similar to Indian-origin than to Chinese-origin animals. The distribution of alleles at 24 short tandem repeat (STR) loci distributed across 17 chromosomes also showed greater similarity between the Nepali and Indian-origin animals. Finally, an analysis of seven major histocompatibility complex (MHC) alleles showed that the Nepali animals expressed Class I alleles that are common to Indian-origin animals, including Mamu-A*01. All of these analyses also revealed a low level of genetic diversity within this Nepali rhesus sample. We conclude that the rhesus macaques of Nepal more closely resemble rhesus macaques of Indian origin than those of Chinese origin. As such, the Nepali rhesus may offer an additional resource option for researchers who wish to maintain research protocols with animals that possess key genetic features characteristic of Indian-origin rhesus macaques.     

Abundance of introduced rhesus macaques (Macaca mulatta) in central Florida

Biological Invasions - Introduced non-human primates threaten native ecosystems and have the potential to transmit diseases to humans and native wildlife, but primate population management is...     

Metagenomic comparison of the rectal microbiota between rhesus macaques(Macaca mulatta) and cynomolgus macaques(Macaca fascicularis)

Rhesus macaques(Macaca mulatta) and cynomolgus macaques(Macaca fascicularis) are frequently used in establishing animal models for human diseases. To determine the differences in gut microbiota between these species, rectal swabs from 20 rhesus macaques and 21 cynomolgus macaques were collected, and the microbial composition was examined by deep sequencing of the 16 S rR NA gene. We found that the rectal microbiota of cynomolgus macaques exhibited significantly higher alpha diversity than that of rhesus macaques, although the observed number of operational taxonomic units(OTUs) was almost the same. The dominant taxa at both the phylum and genus levels were similar between the two species, although the relative abundances of these dominant taxa were significantly different between them. Phylogenetic Investigation of Communities by Reconstruction of Unobserved States(PICRUSt) showed significant differences in the functional components between the microbiota of the two species, in particular the lipopolysaccharide(LPS) synthesis proteins. The above data indicated significant differences in microbial composition and function between these two closely related macaque species, which should be taken into consideration in the future selection of these animals for disease models.     

Behavioral predictors of pairing success in rhesus macaques (Macaca mulatta)

Pair housing is one of the most important components of behavioral management for caged macaques; however, it can result in aggression and injury if partners are incompatible. Knowing when to proceed and when to stop social introductions can be challenging, and can have consequences for the partners. We examined whether behavior early in social introductions predicted success (i.e., partners remained cohoused with full contact for at least 28 days) in 724 female–female and 477 male–male rhesus macaque pairs. We took cage side one–zero focal observations on pairs during the first 2 days of full contact, recording social and aggressive behaviors. The majority of pairs (79.6% of female and 83.0% of male) were successful. The most common behaviors exhibited by pairs during these observations were maintaining proximity, tandem threats, and anxiety. Mounting was also relatively common in male pairs. Grooming and close social contact (e.g., touching) were not common in our study. Several behaviors observed on Day 1 significantly predicted pairing success. For females, these included proximity, tandem threat, rump present, mount, and groom. Day 1 predictors of success for male pairs included proximity, tandem threat, rump present, mount, and social contact. Fewer behaviors predicted success on Day 2. Maintaining proximity on Day 2 predicted success for both sexes, but tandem threat predicted success only for females. Behaviors that predicted incompatibility for females on Day 1 included displace, grimace, threat, bite, and other aggressive contacts. Day 1 predictors of separation for male pairs were displaced, grimace, and abnormal behavior. The only Day 2 behavior that correlated with incompatibility was grimace, which was predictive for males. Interestingly, aggression did not predict incompatibility for male pairs. Identifying behaviors exhibited by monkeys early in the pair introduction that are predictive of long-term compatibility can shape pairing decisions, reducing later stress and potential injury.     

Estradiol increases somatomedin-C concentrations in adolescent rhesus macaques (Macaca mulatta)

Estradiol (E2) may enhance somatomedin-C (Sm-C) secretion during puberty in female rhesus monkeys. The present study evaluated the importance of age and acute changes in E2 on Sm-C secretion. Intact (INT) females at their first ovulation (age 3.5 yr; n = 6) had higher levels of Sm-C across the ovulatory cycle than did intact adults (ADT) (n = 5). Levels of Sm-C were similar for both groups during the follicular and luteal phases despite higher follicular phase levels of E2. Young, ovariectomized, E2-treated (E2OVX) females (age 3.5 yr; n = 5; E2 = 50 pg/ml) had higher basal levels of Sm-C than did either age-matched ovariectomized (OVX) females (n = 3), ovariectomized adults (OXA), or E2-treated ovariectomized adults (E2A) (E2 = 100 pg/ml). When ovariectomized groups were given E2 to induce ovulatory increases, no changes in serum Sm-C occurred. Comparisons among age-mates revealed that basal levels of Sm-C were similar between INT and E2OVX, yet these levels were higher than those for OVX. Sm-C levels were similar among all adult groups. Serum growth hormone (GH) was highest in E2OVX, next highest in INT and OVX, and lowest in all adults. Higher Sm-C levels in young animals are, thus, related to these age differences in GH concentrations and are further enhanced by basal levels of E2 and not by acute changes in this steroid. Low Sm-C secretion in adults is associated with low GH levels. Thus, the facilitory effect of basal E2 on Sm-C release is observed during conditions when basal GH levels are elevated, a situation normally limited to adolescence.     

Early predictors of self-biting in socially-housed rhesus macaques (Macaca mulatta)

The development of self-biting behavior in captive monkeys is little understood and poses a serious risk to their well-being. Although early rearing conditions may influence the expression of this behavior, not all animals reared under similar conditions self-bite. The purpose of this study was to examine the effects of three rearing conditions on biting behavior and to determine whether early infant behavior can predict later self-biting. The subjects were 370 rhesus macaques born at the National Institutes of Health (NIH) Animal Center between 1994 and 2004. They were reared under three conditions: mother-reared in social groups (n=183), peer-reared in groups of four (n=84), and surrogate-peer-reared (n=103). Significantly more surrogate-peer-reared animals self-bit compared to peer-only or mother-reared animals. There was no sex difference in self-biting, but this result may have been affected by a sex bias in the number of observations. The durations of behaviors exhibited by the surrogate-peer-reared subjects were recorded in 5-min sessions twice a week from 2 to 6 months of age while the animals were in their home cages and play groups. In the play-group situation, surrogate-peer-reared subjects who later self-bit were found to be less social and exhibited less social clinging than those that did not self-bite. Home-cage behavior did not predict later self-biting, but it did change with increasing age: surrogate clinging and self-mouthing decreased, while environmental exploration increased. Our findings suggest that surrogate rearing in combination with lower levels of social contact during play may be risk factors for the later development of self-biting behavior.     

Oral papillomas and papilliform lesions in rhesus macaques (Macaca mulatta)

Oral papillomas in two male rhesus macaques that were diagnosed morphologically as filiform and squamous types are described. Two additional macaques had oral papilliform lesions consistent histologically with papillary hyperplasia. Immunohistochemistry, along with electron microscopy and PCR assays, failed to demonstrate evidence of papillomavirus in any of the tumors; however, such results are often lacking when suspect oral lesions in humans and other species are assessed. Other potential causes of the papillary masses include chronic irritation and perhaps a genetic susceptibility. Benign tumors of the oral epithelium in macaques have not been reported previously; they appear to be rare and of variable clinical significance.     

Normative nerve conductions in the tail of rhesus macaques (Macaca mulatta)

BACKGROUND: The aim of this study was to test the feasibility of using the tail of Macaca mulatta for neurophysiological testing of the peripheral nervous system. METHODS: Motor and sensory nerve conduction studies (NCS) of the tail were obtained by surface stimulation and recording. The technique utilized was novel. Unlike other NCS obtained from other peripheral nerves, this technique did not require any special neurophysiological expertise. RESULTS: The latency of the motor and sensory response was 2.5 +/- 0.71 and 1.1 +/- 0.27 ms respectively. The amplitude of the motor and sensory response was 8.1 +/- 5.1 mV and 14.6 +/- 9.4 microV respectively. Similar to human beings, there was a statistically significant relationship between age and motor amplitude, motor latency and sensory latency. CONCLUSIONS: Based on our results, a relatively simple, reproducible neurophysiological monitoring technique of the peripheral nervous system is possible.     

中国猕猴生态学研究进展

中国的灵长类学研究始于19世纪中期之后,而兴盛于20世纪80年代至今。猕猴（Macaca mulatta）是世界及中国分布最为广泛的一种非人灵长类动物,在中国境内分布于17个省（市、区）,已被列为国家二级重点保护野生动物。迄今为止,学者们已对猕猴进行了包括地理分布、种群动态、食性、社会生态、保护生态等多方面的研究。本文拟对国内有关猕猴生态学方面的研究工作进行回顾与综述,以期通过对以往工作的汇总,梳理关于猕猴的研究线索与动态,并对今后的研究有所启示。