Characteristics and regulation of the ovarian cycle in vervet monkeys (Chlorocebus aethiops)

This study was designed to evaluate the timecourse of ovarian and pituitary endocrine events throughout the menstrual cycle in the vervet monkey, and whether circulating luteinizing hormone (LH) or the uterus regulates the functional lifespan of the vervet corpus luteum. Daily saphenous blood samples were collected from adult females (1) during spontaneous menstrual cycles (n = 7), and (2) during cycles in which a gonadotropin-releasing hormone antagonist (acyline) was administered for 3 days at midluteal phase (n = 3), and (3) for 30 days following recovery from hysterectomy (n = 4). Estradiol (E) and progesterone (P) levels were assayed using electrochemoluminescent assays. Gonadotropin levels were measured by radioimmunoassay using reagents developed for the assay of follicle-stimulating hormone and LH in macaques. Spontaneous cycles exhibited a midcycle E rise (476+/-49 pg/ml), engendering an LH surge, 12+/-1 days after onset of menses, followed by a luteal phase with peak P levels of 4.7+/-0.9 ng/ml. Histologic evaluation of the ovaries at late follicular phase or early luteal phase revealed the presence of a single, large Graafian follicle or developing corpus luteum, respectively. Acyline treatment caused a significant (P<0.05) decline in P levels (2.9+/-0.5 vs 0.5+/-0.3 ng/ml, 0 vs 48 h post-treatment) and premature menstruation compared with untreated controls (P<0.05). Hysterectomy had no apparent effect on the monthly pattern or levels of circulating E or P. Thus, the characteristics and regulation of the ovarian cycle in vervets appear similar to those in women and macaques, with cyclicity dependent on pituitary gonadotropin hormones and independent of a uterine luteolytic factor.     

Hematological changes in vervet monkeys (Chlorocebus aethiops) during eight months' adaptation to captivity

This study investigated fluctuations in hematological values of 50 wild-caught vervet monkeys (African green monkeys, grivets, Chlorocebus aethiops) during habituation to captivity. The monkeys were categorized into four groups according to age and sex viz adult males, adult females, juvenile males, and juvenile females. The erythrocyte values were significantly higher (P<0.05) in the adult males than in the other animals. There was an increase in most of the erythrocyte parameters studied during the monitoring period with the most significant being hemoglobin, hematocrit, and mean corpuscular volume. However, the red cell distribution widths, which were higher in adult females, declined. The total white blood cell (WBC) counts, which were higher in adult females than in the other animals, were closely correlated with granulocytes counts. The WBC levels decreased in all the animals throughout the 8 months study, indicating gradually decreasing stress, but they were relatively stable in males. The platelet counts declined significantly (P<0.05) and at 8 months post capture the counts were higher in females than in males. The juvenile female platelet counts were relatively stable during the monitoring period. The maintenance of the monkeys on an improved stable diet and in environment-controlled housing combined with progressing psycho-physiological adaptation may be important factors for the gradual improvements of the hematological values recorded. There were wide variations in these between individual animals emphasizing the need for long adaptation combined with establishment of individual baseline values before experimental studies.     

Contact with human facilities appears to enhance technical skills in wild vervet monkeys (Chlorocebus aethiops)

Technical abilities of primates are typically tested in the laboratory. It has been argued that close contact between animals and humans may lead to an increase in skills due to an 'enculturation' of subjects. Here, we provide evidence that exposure to human facilities may improve wild vervet monkeys' technical skills in a social learning task using the 'artificial fruit' approach. Two of our 6 study groups had access to human facilities within their territories. Only members of these 2 groups were likely to open successfully 'artificial fruit' during their first attempt. Success appeared to be independent of individual sex or the type of task. Our results highlight the possibility that human enculturation may allow captive monkeys to acquire more technical skills than their wild counterparts, and we suggest that this possibility should be tested in further field experiments.     

Probable genetic origin for a large number of cataracts among captive-bred vervet monkeys (Chlorocebus aethiops)

During a period of 6 years, uni- or bilateral cataracts occurred in 55 captive-bred vervet monkeys, representing 27.6% of all offspring produced in that time. Fifty-eight percent of all cases were detectable only by ophthalmoscopy. A total of 30% of cases were offspring of wild-caught parents, 40% from first-generation captive-bred parents, 4% from second-generation captive-bred parents, and 26% from parents of which one was wild caught. Cataracts that could be observed macroscopically appeared at about 6-8 mo of age. A sample of juvenile vervet monkeys with cataracts and their parents had no antibodies against rubella virus, herpes simplex virus, or toxoplasma gondi, and all except two wild-caught breeding females had no antibodies against cytomegalovirus. Plasma vitamin D3 (25 [OH] D), calcium, phosphorus, and glucose concentrations of six cataract cases were comparable to a control group of healthy individuals. The exclusion of these extraneous factors, as well as the fact that the majority of all cases were related, was considered evidence of hereditary etiology. Males and females that had either produced offspring with cataracts or were related to individuals with cataracts were replaced. To date, 35 babies have been born, and no new cases have since occurred.     

Vitamin A toxicity in wild-caught African green vervet monkeys (Chlorocebus aethiops) after 2 years in captivity

Primate lab diets typically contain high vitamin A concentrations when compared with human recommended intakes. In this study, we analyzed the vitamin A contents of liver and serum from 13 adult female African green vervet monkeys (Chlorocebus aethiops). These monkeys were wild-caught and held in captivity for 2 y, during which time they consumed a standard primate diet. Liver vitamin A concentration (mean +/- 1 standard deviation) was 14.6 +/- 2.3 micromol retinol/g liver; subtoxicity in humans is defined as at least 1 micromol/g liver. The serum retinol concentration (0.93 +/- 0.21 microM) was not elevated. Hypertrophy and hyperplasia of hepatic stellate cells were present which, in conjunction with elevated hepatic vitamin A concentrations, are evidence of toxicity. Although the ramifications of chronically toxic vitamin A status in experimental monkeys have not been defined, this state may influence nonhuman primate research outcomes and confound data interpretation. The validity of bone mineral research using nonhuman primates is of greatest concern, in light of the association between vitamin A toxicity and compromised bone health.     

Steroid hormone influences on the mating behavior of vervet monkeys (Cercopithecus aethiops)

Eight ovariectomized female vervet monkeys (Cercopithecus aethiops) were tested in heterosexual and isosexual pairs, under estradiol and testosterone treatments. Pairs were tested under two different experimental situations in which the male was either restrained or left free. There were only small behavioral changes across the treatments, involving mainly male responses. Erection time, frequency of intromission, ejaculation, and olfactory investigation increased during estradiol treatment whereas during administration of testosterone erection time, the number of approaches, contacts, and olfactory investigations decreased. Female behaviors were relatively independent of hormone treatment showing only the disappearance of negative responses with estradiol and an increase of yawns with testosterone. Female behaviors were performed at a higher level with male partners than with other females, and the frequencies of spontaneous presents varied with the sex of partner. It is suggested that in vervet monkeys both estradiol and testosterone affect female attractivity, estradiol further influences receptivity, whereas proceptivity appears to be less directly involved in sexual interactions and more related to social context.     

Longitudinal stability in adult status hierarchies among vervet monkeys (Cercopithecus aethiops)

Status hierarchies were examined in a captive group over a 12-year period (1968–1979) to establish the stability and structure of vervet monkey dominance relationships. Dyadic records of spontaneous avoid, bite, chase, and supplant behaviors are summarized into a win/lose matrix to produce a rank order of status at the end of each calendar year. The 13,717 agonistic acts tabulated are drawn from both focal and ad lib data. Relative rank is computed by dividing the rank position of each individual by the number of individuals ranked for that year. Relative rank was found to be quite stable for adults of both sexes, although males were more variable than females. There was a strong matinrline effect on all captive born animals' rank position. No gender difference in rank was demonstrable. Infants were very subordinate at the end of their first year, but rose to positions near those of their mothers by the end of the fourth year. Presence or absence of canine teeth had no demonstrable effect on status. The results emphasize the relative importance of social learning in the establishment and maintenance of dominance relationships. The apparent gender difference in rank among wild living vervets is hypothesized to be a consequence of the male intergroup mobility. If a male is restrained from emigration, he is strongly affected by his mother's rank as he establishes his own dominance position in the troop.     

A genetic linkage map of the vervet monkey (Chlorocebus aethiops sabaeus)

The spectacular progress in genomics increasingly highlights the importance of comparative biology in biomedical research. In particular, nonhuman primates, as model systems, provide a crucial intermediate between humans and mice. The close similarities between humans and other primates are stimulating primate studies in virtually every area of biomedical research, including development, anatomy, physiology, immunology, and behavior. The vervet monkey (Chlorocebus aethiops sabaeus) is an important model for studying human diseases and complex traits, especially behavior. We have developed a vervet genetic linkage map to enable mapping complex traits in this model organism and facilitate comparative genomic analysis between vervet and other primates. Here we report construction of an initial genetic map built with about 360 human orthologous short tandem repeats (STRs) that were genotyped in 434 members of an extended vervet pedigree. The map includes 226 markers mapped in a unique order with a resolution of 9.8 Kosambi centimorgans (cM) in the vervet monkey genome, and with a total length (including all 360 markers) of 2726 cM. At least one complex and 11 simple rearrangements in marker order distinguish vervet chromosomes from human homologs. While inversions and insertions can explain a similar number of changes in marker order between vervet and rhesus homologs, mostly inversions are observed when vervet chromosome organization is compared to that in human and chimpanzee. Our results support the notion that large inversions played a less prominent role in the evolution within the group of the Old World monkeys compared to the human and chimpanzee lineages. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

Fire and home range expansion: A behavioral response to burning among savanna dwelling vervet monkeys (Chlorocebus aethiops)

The behavioral adaptations of primates to fire‐modified landscapes are of considerable interest to anthropologists because fire is fundamental to life in the African savanna—the setting in which genus Homo evolved. Here we report the behavioral responses of a savanna‐dwelling primate, vervet monkeys (Chlorocebus aethiops), to fire‐induced ecological change. Using behavioral and spatial data to characterize ranging patterns prior to and postburn and between burn and nonburn years, we show that these primates inhabiting small, spatially bound, riverine habitats take advantage of newly burned savanna landscapes. When subjects encountered controlled fires, they did not flee but instead avoided the path of the fire seemingly unbothered by its approach. After fire, the primates' home range expanded into newly burned but previously unused areas. These results contribute to understanding the response of non‐human primates to fire‐modified landscapes and can shed light on the nature and scope of opportunities and constraints posed by the emergence of fire‐affected landscapes in the past. Results also expose deficiencies in our knowledge of fire‐related behavioral responses in the primate lineage and highlight the need for further investigation of these responses as they relate to foraging opportunities, migration, resource use, and especially fire‐centric adaptations in our own genus. Am J Phys Anthropol 154:554–560, 2014. © 2014 Wiley Periodicals, Inc.     

Leptospires in vervet monkeys (Cercopithecus aethiops Sabaeus) on Barbados

Agglutinins to Leptospira were found at titers of greater than or equal to 1:100 in 150 of 501 (29.9%) vervet monkeys (Cercopithecus aethiops sabaeus) bled within 1 mo of capture in Barbados. Including a further 34 of 145 bled within 1 yr of capture, the seropositivity prevalence was 28.5%. A further 35 monkeys (5.4%) had traces of agglutinins or gave titers of 1:50. The proportion of seropositive adults (41.5%) was more than twice that of seropositive immature monkeys (17.6%). Among adults, 49.2% of males and 35.7% of females were seropositive, while among juveniles proportions of seropositive males and females were similar (17.8% and 17.4%, respectively). Seropositivity prevalences tended to increase in proportion to rainfall. In each of 165 of the 184 positive sera, a single serogroup predominated in the serological reactions. These serogroups were Ballum (61%), Icterohaemorrhagiae (16%), Autumnalis (15%), Pyrogenes, Panama, Pomona, Tarassovi and Canicola (8% altogether). In the other 19 positive sera no single serogroup predominated. Serial bleeding showed that vervet monkeys can retain naturally-acquired antibodies to Leptospira for at least 2.5 yr. The evidence suggests that vervet monkeys in Barbados are transmitting leptospiral infections among themselves independently of other groups of animals, and are not a major source of human leptospirosis.     

Decreased global DNA methylation in the white blood cells of high fat diet fed vervet monkeys (Chlorocebus aethiops)

Epigenetic mechanisms are associated with the development of many chronic diseases and due to their reversible nature offer a unique window of opportunity to reverse the disease phenotype. This study investigated whether global DNA methylation correlates with dysglycemia in the vervet monkey (Chlorocebus aethiops). Diet-induced changes in DNA methylation were observed where global DNA methylation was twofold lower in monkeys fed a high fat diet (n?=?10) compared to monkeys fed a standard diet (n?=?15). An inverse correlation was observed between DNA methylation, blood glucose concentrations, bodyweight, and age, although the association was not statistically significant. Consumption of a high fat diet is associated with the development of metabolic disease; thus, these results suggest the use of global DNA methylation as a biomarker to assess the risk for metabolic disease. Moreover, this study provides further support for the use of the vervet monkey as a model system to study metabolic diseases such as type 2 diabetes. Integration of altered DNA methylation profiles into predictive models could facilitate risk stratification and enable intervention strategies to inhibit disease progression. Such interventions could include lifestyle modifications, for example, the increased consumption of functional foods with the capacity to modulate DNA methylation, thus potentially reversing the disease phenotype and preventing disease.     

Pregnancy outcome in free-ranging vervet monkeys (Cercopithecus aethiops)

A preliminary assessment of individual female differences in conception rate and fetal wastage has been determined for a population of wild vervet monkeys (Cercopithecus aethiops). One of three troops of vervet monkeys, the subjects of a long-term behavioral study, was trapped and blood was obtained for electrophoretic analysis. Pregnant females exhibited a distinctive serum aminopeptidase phenotype allowing a conclusive determination of pregnancy. Of the seven females diagnosed as pregnant, three later gave birth. Of the females that aborted, two were nulliparous and one was very old. Studies of captive animals have indicated that age and rank may affect a female's ability to carry a fetus to term. These factors, rather than the trapping procedure, may have been responsible for most of the fetal loss in the trapped troop. A comparison of all three troops for a 3-year period indicated that there were fluctuations in yearly birth success of individual females, as well as a relatively high miscarriage rate. The results of this study indicate the advantages of obtaining joint behavioral and biological data.     

Serum aminopeptidases in pregnant vervet monkeys (Cercopithecus aethiops)

Two distinctive aminopeptidase isozymes have been identified in the serum of the vervet monkey. The l-methionine-sensitive cytosol aminopeptidase (AP; E.C. 3.4.11.1) is present in all samples, while the cystyl aminopeptidase (CAP; E.C. 3.4.11.3) isozyme, which is resistant to inhibition by 0.1 m l-methionine, is found only in the serum of pregnant females. The pregnancy-specific CAP isozyme appears in the serum between the fifth and the eleventh weeks of a nearly 22-week pregnancy. The overall aminopeptidase activity and the activity of the l-methionine-insensitive isozymes alone are both significantly greater in the serum of pregnant females than in nonpregnant females. Consequently, the presence of the cystyl aminopeptidase isozyme in the serum is a useful diagnostic indicator of pregnancy in the vervet monkey.     

Diet and dominance among female vervet monkeys (Cercopithecus aethiops)

Behavioral observations of free-ranging female vervet monkeys (Cercopithecus aethiops) suggest that priority of access to food enhances individual fitness. Seventeen adult females living in two social groups were observed for 26 months in the Samburu/Isiolo Game Reserves, northern Kenya. Priority of access to feeding and sitting sites was associated with significant differences in diet and reproduction. Food species distribution altered rank-related differences in diet. Rank-related differences in diet occurred when food items were clumped in distribution, but not when they were randomly distributed. The relation of individual food items to reproduction influenced rank-related differences in reproduction. Rank was significantly correlated with birth rate when a preferred food species was clumped in distribution.