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.     

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.     

Rank,relationships, and responses to intruders among adult male vervet monkeys

We examined the influences of dyadic relationships among captive adult male vervet monkeys (Cercopithecus aethiops sabaeus) on behavior directed toward caged “intruder” males placed inside subjects' enclosures. Subjects were all 9 adult male residents from three stable social groups, each of which contained 3 adult males, at least 3 adult females, and their immature offspring. Every male was observed in two 3-hour sessions, each time with one of the 2 other adult males from his group. Observation sessions consisted of six consecutive 30-min stages in which group composition and the presence of the intruder were manipulated. All groups exhibited a stable, linear male dominance hierarchy prior to and throughout the study. In each group, there was one pair of males, when together, in which each member exhibited higher rates of intruder-directed approach and aggressive behaviors than when either animal was paired with the third male of his social group. Such pairs were also distinguished by high levels of within-pair agonistic interactions. The higher-ranking member of each dyad was the most aggressive male toward the intruder in his social group, although only one of these animals was the dominant male of his group. Mutual facilitation of aggression against intruding males is interpreted as cooperative behavior benefitting both males by increasing the likelihood of repelling a potential competitor for resident females. Such cooperation provides further evidence in nonhuman primates for cohesive male-male dyads between animals whose social interactions are characterized by agonism. © 1993 Wiley-Liss, Inc.     

Resting cortisol levels and the emergence of dominant status among male vervet monkeys

Resting serum cortisol was measured in adult male vervet monkeys (Cercopithicus aethiops sabaeus) in four different conditions: (1) among groups with unaltered group membership and established dominance hierarchies; (2) among groups from which the original dominant male had been removed and in which the remaining males competed for dominant status; (3) among newly formed groups of three unfamiliar males each of which had been the dominant male in his previous group; and (4) among groups from which a dominant male was temporarily separated and returned. In Condition 1, cortisol concentrations did not differ between dominant and subordinate males. The second condition showed that cortisol levels were highest among males who eventually emerged as the dominant male. In the third condition, however, cortisol levels did not differentiate eventually dominant from eventually subordinate males. In the last condition, cortisol levels were highest in the animals that became or remained dominant following reintroduction. These data indicate that cortisol concentration does not differ between dominant and subordinate males in stable groups and that cortisol rises during competition for dominance among familiar males.     

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.     

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.     

Genital signalling and the coexistence of male vervet monkeys (Cercopithecus aethiops pygerythrus)

To ascertain the social significance of male genital colouration two troops of vervets, one free-ranging and one caged, were observed. It was found that genital signals were associated with intermale agonism. It is suggested that this communicatory system regulates the behaviour of competitors and may thereby have facilitated the evolution of a multimale social system.     

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.     

The effects of temporary removal of the alpha male on the behavior of subordinate male vervet monkeys

The effects of temporary removal of the alpha male on the behavior of subordinate adult male vervet monkeys were evaluated. Twelve subordinate males from six captive multimale, multifemale vervet monkey groups were observed in two conditions: when all group members were present and when the alpha male was temporarily removed from each group. In the absence of the alpha male, subordinate males initiated more affiliative behavior and increased the amount of time spent in proximity to females but their rates of aggression were unaltered. Increased affiliative behavior was selectively directed to high-ranking females and their offspring. Under removal conditions, subordinate male behavior did not resemble that of alpha males in intact conditions: they differed in their proximity to and affiliative behavior towards other group members. In the absence of the alpha male, females increased their aggression towards subordinate males. These observations suggest that the presence of alpha males strongly inhibits subordinate males' behavior. When the constraints of the alpha male's presence are removed, subordinate males rapidly engage in behavior that may enhance their likelihood of attaining high rank. In combination with prior studies, the data also indicate that the behaviors involved in the maintenance of high rank by alpha males differ from those subordinates use to acquire dominance. Finally the current study supports the view that aggression by female vervets may be highly influential in determining male ascendency to dominant rank.     

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.     

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.     

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.     

Determinants of fecundity and reproductive success in captive vervet monkeys

Between 1975 and 1983, adult female vervet monkeys (Cercopithecus aethiops sabaeus) over 3.5 years of age, living in two undisturbed social groups in a captive colony in Sepulveda, California, have averaged 1.0 births per female year with a mean interbirth interval of 10.7 months. Increased fecundity did not result in decreased survival rates of offspring in this population. Fecundity was influenced by the mother's age and dominance rank. The primary factor in the age-fecundity relationship was the age at first birth, which varied from three to five years. High-ranking females contributed the most to the high rate of fecundity, with significantly shorter interbirth intervals, more births per female year, and more surviving infants compared to low-ranking females.     

Maternal protectiveness and response to the unfamiliar in vervet monkeys

Vervet monkeys (Cercopithecus aethiops sabaeus) show individual differences in approach-avoidance behavior when faced with an unfamiliar and potentially threatening situation. Prior research from our colony demonstrated that juveniles who had experienced high levels of early maternal protectiveness were more cautious in response to novelty, compared to juveniles who had had less protective mothers. The research reported here was designed to verify this result in a paradigm that experimentally varied maternal protectiveness through the introduction of new breeding adult males. Mothers responded to the presence of new males by increased maternal protectiveness toward infants born in the year following the introductions. Individual differences in response to the unfamiliar were later evaluated by measuring the latency to approach within 1 m of novel food containers placed into the home enclosure of four naturally composed social groups. Infants approached with the same latency and in the same order as their mothers. Juveniles approached sooner than, and independent of, their mother's current behavior, but their latency to approach could be predicted by the experimentally induced variation in maternal protectiveness they had experienced as infants. Immatures who had been born in New Male years, when maternal protectiveness was high, were more cautious and had significantly longer latencies to approach the novel stimulus compared to immatures who had been born in Resident Male years. © 1993 Wiley-Liss, Inc.