Vocal recognition in free-ranging vervet monkeys

Screams of free-ranging juvenile vervet monkeys were played to a group containing their mothers and two ‘control’ females who also had offspring in the group. Mothers and controls were separated from their offspring at the time. Mothers' responses showed significantly shorter latency and longer duration than controls'; mothers were also significantly more likely to approach the speaker. Playbacks significantly increased the probability that controls would look at the mother; a majority of controls did so without any apparent cue from the mother. Results demonstrate that adult female vervets can distinguish their offsprings' screams from those of other immatures, and they suggest that vervets are able to associate specific screams with specific individuals and these individuals with their mothers.     

Semen characteristics of vervet monkeys

Semen samples (91) from 47 vervet monkeys were collected by electroejaculation over a 2 year period. Seventy-eight of these were from 37 singly caged males of unknown fertility and 13 from 10 breeding males of known fertility. Mean values for semen characteristics of the singly caged males were: volume 0.45 ml, pH 7.8, concentration 184 x 10(6)/ml, forward progression rating 2.95 (scale 0-4), motility 55.4%, live 68% and abnormal morphology 3.5%. Mean values for semen characteristics for the breeding males were: volume 0.86 ml, pH 9.00, concentration 117.15 x 10(6)/ml, forward progression rating 3.00 (scale 0-4), motility 43.6%, live 53.3% and abnormal morphology 6%. Semen volumes in the singly caged males were lower than the volumes reported in other studies.     

Drinking competition in vervet monkeys

During a period of water shortage, adult female and adult male vervet monkeys (Cercopithecus aethiops) obtained water by different methods. Females drank from tree-holes within their normal home range, while males invaded the territories of neighbouring groups. Higher-ranking females had access to preferred tree-holes. The mortality rate was high in both sexes and was greater in low-ranking than in high-ranking animals.     

Psorergatic acariasis in vervet monkeys

7 cases of acariasis were discovered amongst a colony of vervet monkeys (Cercopithecus pygerythrus). Lesions were confined to palpebrae and periorbital areas. Skin scrapings and biopsies were taken and the parasite was identified as Psorergates cercopitheci. The skin biopsies showed that the parasite invaded the superficial epidermis only. Skin scrapings taken from other parts of the infested animals' bodies were all negative for mites. Several of the infested animals have had physical contact with conspecifics, the majority of which have remained uninfested. Topical treatment was effective and often eradicated the mite completely after only one treatment.     

Selective attention to philopatric models causes directed social learning in wild vervet monkeys

Human behaviour is often based on social learning, a mechanism that has been documented also in a variety of other vertebrates. However, social learning as a means of problem-solving may be optimal only under specific conditions, and both theoretical work and laboratory experiments highlight the importance of a potential model''s identity. Here we present the results from a social learning experiment on six wild vervet monkey groups, where models were either a dominant female or a dominant male. We presented ‘artificial fruit’ boxes that had doors on opposite, differently coloured ends for access to food. One option was blocked during the demonstration phase, creating consistent demonstrations of one possible solution. Following demonstrations we found a significantly higher participation rate and same-door manipulation in groups with female models compared to groups with male models. These differences appeared to be owing to selective attention of bystanders to female model behaviour rather than owing to female tolerance. Our results demonstrate the favoured role of dominant females as a source for ‘directed’ social learning in a species with female philopatry. Our findings imply that migration does not necessarily lead to an exchange of socially acquired information within populations, potentially causing highly localized traditions.     

The genetic consequences of primate social organization: a review of macaques,baboons and vervet monkeys

Primates, as long-lived, iteroparous, socially complex mammals, offer the opportunity to assess the effects of behavior and demography on genetic structure. Because it is difficult to obtain tissue samples from wild primate populations, research in this area has largely been confined to terrestrial and semi-terrestrial old world monkeys (e.g., rhesus and Japanese macaques, vervets and several subspecies of baboons). However, these species display a multi-male, multi-female social structure commonly found in many other primate and non-primate mammals. Electrophoretic analyses of blood proteins from individually recognized and/or marked wild Himalayan rhesus monkeys, themselves the subject of long-term behavioral and demographic research, have begun to reveal the genetic consequences of such phenomena as social group fission, malelimited dispersion, non-consanguineous mating patterns, and agonistically defined male dominance.Specifically, rhesus social groups, consisting primarily of clusters of maternal relatives, appear to be nonrandom samples of a population's genotypes and genes. The genetic effects of social group fission are highly dependent on each group's size, demographic structure, and average degree of relatedness. In all cases fission contributes to the degree of intergroup genetic differentiation. Male-limited dispersion appears both to retard genetic differentiation between social groups and to lead to mating patterns that result in an avoidance of consanguinity. Groups, therefore, appear to be genetically outbred.Comparing these results with studies of other free-ranging or wild cercopithecines allows several generalizations: (a) genetic variation seems to be evenly distributed throughout each local population of multi-male social groups; (b) social groups, however, because they contain clusters of relatives, are distinctive in their specific frequencies of genes; (c) the degree of genetic differentiation between a population's social groups, because of the effects of social group fission and non-deterministic forms of male dispersal, is somewhat greater than expected on the basis of migration rates alone; and (d) the asymmetrical pattern of dispersion with respect to sex effectively precludes inbreeding in any one social group or the population as a whole. These observations have important implications for understanding the unusually rapid rates of evolution among the primates.     

Anatomic brain asymmetry in vervet monkeys

Asymmetry is a prominent feature of human brains with important functional consequences. Many asymmetric traits show population bias, but little is known about the genetic and environmental sources contributing to inter-individual variance. Anatomic asymmetry has been observed in Old World monkeys, but the evidence for the direction and extent of asymmetry is equivocal and only one study has estimated the genetic contributions to inter-individual variance. In this study we characterize a range of qualitative and quantitative asymmetry measures in structural brain MRIs acquired from an extended pedigree of Old World vervet monkeys (n = 357), and implement variance component methods to estimate the proportion of trait variance attributable to genetic and environmental sources. Four of six asymmetry measures show pedigree-level bias and one of the traits has a significant heritability estimate of about 30%. We also found that environmental variables more significantly influence the width of the right compared to the left prefrontal lobe.     

Diagonal walking in captive infant vervet monkeys

The frequency of use of diagonal walking by three motorically immature vervet monkeys (Cercopithecus aethiops) is discussed. The subjects were housed at The Balcones Research Center (Austin, Texas) and ranged from 15–105 days of age. Mixed longitudinal data taken from film indicated that lateral walknig was the first gait employed by the infant vervets studied, but that diagonal walking completely replaced lateral walking by 81 days of age. These data were compared with those of captive infant Macaca mulatta, and feral infant Papio anubis. General agreement was found regarding onset and frequency of use of diagonal walking in the three genera.     

Alloparental care and kinship in captive social groups of vervet monkeys (Cercopithecus aethiops sabaeus)

Estimates of alloparental behavior on the basis of kinship and maternal qualities of permissiveness/restrictiveness were examined in vervet mother-infant pairs. Amounts of alloparenting were examined for the subgroup categories female siblings, juvenile females, subadult nulliparous females, adult females, males, and yearlings. Analysis of the six subgroups for months 1 through 6 revealed that the most alloparenting occurred in month 1 with siblings caretaking more than any other subgroup. By month 2 subadult nulliparous females were the most frequent caretakers. Correlations between kin alloparenting and maternal permissiveness/restrictiveness indicated that kinship was a better predictor of alloparenting than maternal qualities of permissiveness. Additionally, examination of the data on maternal behaviors towards related and unrelated individuals revealed significant differences by months.     

Early development of locomotor behavior in vervet monkeys

The locomotor development of three vervet infants across approximately the first 2 months of life is described. Fairly normal-looking walking movements (as compared to adults) were seen in all the animals by approximately 1 month of age and galloping was observed by 2 months. Early locomotor footfall patterns were often aberrant and bounding-type gaits were sometimes exhibited. Most of the symmetrical gaits observed were classifiable as lateral sequence. Across the 2-month period the animals showed decreased three- and four-foot support and improvements in joint angular displacement patterns. From their earliest locomotor movements the infants showed significant linear relationship between both cycle duration and swing and stance durations of the limbs. We suggest that locomotor control mechanisms are probably fairly mature at birth but that weight support and postural control problems explain the initial locomotor difficulties exhibited by these infants.     

Technical note: Urine collection from vervet monkeys by instrumental conditioning

Gang-caged adult male vervet monkeys were trained to urinate on demand into a plastic beaker by positive reinforcement (peanut rewards). The animals were not separated from their social group during training or sampling.     

Assessment of meaning and the detection of unreliable signals by vervet monkeys

Free-ranging vervet monkeys, Cercopithecus aethiops, who had learned to ignore playbacks of one type of call by an unreliable signaller subsequently also ignored playback of an acoustically different call by the same individual if the calls had similar referents. Such transfer did not occur if either the identity of the signaller changed or if the two calls had different referents. After repeatedly being played an intergroup call in the absence of other groups, vervets also ignored an acoustically different intergroup call given by the same individual. The monkeys did not transfer habituation, however, if the new call was given by a different individual. In tests where the referents of two calls were different, the monkeys also failed to transfer habituation across call types. Vervet monkeys who had learned to ignore an unreliable leopard alarm call did not later ignore an eagle alarm call, even when the signaller remained the same. Results suggest that vervets, like humans, process information at a semantic, and not just an acoustic, level.     

Selection of secondary growth areas by vervet monkeys (Cercopithecus aethiops)

Habitat selection by a group of vervet monkeys (Cercopithecus aethiops) living on the savanna peninsula of St. Kitts was investigated by the intensive sampling of 12 transects. The vervets exhibited nonrandom use of habitats. Examination of 20 ecological variables in each of the habitat types revealed that the vervets preferentially used areas of secondary growth characterized by high density and diversity of tall food plants. It is suggested that the preferential use of secondary growth habitat can be attributed to the fact that these areas have high levels of plant productivity and that they have a large proportion of their productivity available for consumption.     

Group extinction and fusion in free-ranging vervet monkeys

Three cases of group fusion were observed among vervet monkeys in Amboseli National Park, Kenya, during the 1984 drought. In all cases, group fusion involved the migration of at least two females into a small neighboring group. Following migration, the females' natal groups ceased to exist. Although migrants initially assumed low ranks, none received high rates of aggression, and two rose in rank 6 months after their arrival. Migrant females appeared to employ a number of “strategies,” including grooming, allomothering, participation in intergroup encounters, and the formation of coalitions against males and each other to hasten integration. Results suggest that the causes of male and female migration differ fundamentally, and that group fusion occurs primarily in response to the inability of small groups of females to compete successfully with other groups for resources.     

Voluntary consumption of substances of unknown palatability by vervet monkeys: a refinement

BACKGROUND: Pure compounds and herbal medicines, had to be administered orally to vervet monkeys for testing. A reliable method was sought to avoid daily gavaging. METHODS: Substances were incorporated into the maize meal based diet of this facility for voluntary consumption. Food intake was monitored. RESULTS: In all but one case, consumption of the treated food was in excess of 90%. In all cases, the purpose of the study was achieved. Habituation was usually only required to the vehicle, and was accomplished by incremental increases to the desired concentration. Aversion was overcome by the addition of a small amount of honey. Plasma concentrations of a compound metabolite could be measured in one case after gavage and food consumption, and were similar for both methods. CONCLUSION: The method enables reliable voluntary consumption of diverse substances. Since stressful gavaging is avoided, it is a valuable contribution to the 3Rs.     

Acute changes in social composition and agonistic behavior in male vervet monkeys (Cercopithecus aethiops sabaeus)

Among nonhuman primates the composition of social groups influences the interactions of group members. We assessed the effects of acute changes in social composition on behavior among 15 adult male vervet monkeys (Cercopithecus aethiops sabaeus). Subjects were observed in their basal social groups which comprised 3 adult males, 2–4 adult females, and offspring; and in two subgroups consisting of either two or three adult males. Agonism and vigilance increased in smaller groups relative to basal conditions, while subjects in two-male groups displayed more aggression than those in three-male groups. These findings suggest that, among male vervet monkeys, acute disruption of stable social groups increases aggressive behavior, and that the amount of agonism is influenced by the composition of the consequent subgroups. © 1992 Wiley-Liss, Inc.     

The ontogeny of social play in a feral troop of vervet monkeys (Cercopithecus aethiops sabaeus): The function of early play

We describe the ontogeny of social play over the first 30 weeks of age in a troop of feral vervet monkeys (Cercopithecus aethiops sabaeus) in Barbados. Play time increased rapidly for the first 10 weeks but remained relatively constant thereafter. The form of play changed with infant age; bouts became more frequent but of shorter duration. Play time, bout frequency, and bout duration at a given age differed between infants; younger infants altered their play patterns to complement those of older infants. All infants played more within their own year class than with older juveniles; play time increased with decreasing age difference between the infant and the play partner. Infants terminated a higher proportion of their play bouts the greater the age difference between themselves and their play partners. Preferred play partners are therefore individuals of similar age that will be similar in size and have matched motivation to play and form of play. Neither play time nor proportion of bouts initiated or terminated was correlated with the social rank of the play partner, which suggests that play is not directed toward individuals that may be high-value alliance partners. Maternal intervention in play occurred primarily when infants were<10 weeks old. It was not correlated with the age or social rank of the mother or with the age or social rank of her infant's play partner. Infants played more and terminated a lower proportion of their play bouts in the absence of their mothers than in their presence. Our results are consistent with the hypothesis that the primary function of early play is to enhance physical fitness and to develop coordination and other fighting skills, with minimal risk of injury.     

Species recognition by five macaque monkeys

Sixteen monkeys of five macaque species (Macaca fuscata fuscata, M. mulatta, M. radiata, M. nemestrina, andM. arctoides) pressed a lever to see a variety of pictures (35 mm slides) of seven macaque species including their conspecifics. The subjects were allowed to see the same picture for the duration of the lever press and were able to see the same picture repeatedly by pressing the lever within 10 sec after the previous release of the lever. When 10 sec passed after releasing the lever, the next picture was set on the slide projector. All monkeys exceptM. arctoides and two infantM. fuscata fuscata pressed the lever to see their conspecifics for the longest duration. For all of the adult subjects, a multivariate analysis of variance (MANOVA) based on the mean duration of lever pressing responses (D) and the mean interval between the responses (I) revealed that the data for conspecific stimuli were distributed at significantly different locations from those for at least one of six close species on a two-dimensional space constructed with D and I. These results suggest that adult macaque monkeys visually discriminate their conspecifics from close species based on the still images of them.     

Hepatic estrogen-binding proteins in male and female vervet monkeys

Hepatic cytosols from male and female vervet monkeys (Cercopithecus pygerythrus) were found to contain the same levels of high affinity estrogen-binding proteins. Multipoint saturation analyses revealed that male liver cytosols contain two distinctly different binding components: a high affinity (HAEB) and a low affinity estrogen binder (LAEB). Female livers appeared to contain only the HAEB. Sucrose density gradient (SDG) analyses, however, clearly established the presence of a 3.8 S as well as an 8.1 S estrogen-binding component in the hepatic cytosols of both sexes. The 3.8 S binding component appeared to be more prominent in male SDG profiles. Cytosols, prepared in the presence of sodium molybdate (cyt +) exhibited significantly lower (50%) levels of specific estrogen-binding than cytosols prepared in the absence of the oxyanion (cyt-). SDG analyses, however, indicated that in cyt+ the 8.1 S binding component was stabilized at the cost of the 3.8 S binder. This phenomenon was observed in both sexes. Large excess levels of cortisol did not have any effect on specific estrogen binding by hepatic cytosols. The hepatic estrogen-binding proteins displayed a lower relative binding affinity for diethylstilbestrol than for its native ligand and higher affinities for estriol and estrone than expected.