Intraspecies variation in dominance style of Macaca fuscata

Knowledge of intraspecific variation is important to test the evolutionary basis of covariation in primate social systems, yet few reports have focused on it, even in the best-studied species of the Macaca genus. We conducted a comparative study of the dominance styles among three provisioned, free-ranging groups of Japanese macaques at Shodoshima Island, Takasakiyama Mountain and Shiga Heights, and collected standard data on aggressive and affiliative behavior during a period of 5 years. Our data in the Takasakiyama and Shiga groups support previous studies showing that Japanese macaques typically have despotic social relations; nevertheless, our data in the Shodoshima group are inconsistent with the norm. The social traits of Shodoshima monkeys suggested that: (1) their dominance style is neither despotic nor tolerant but is intermediate between the two traits; (2) some measures of dominance style, e.g., frequency and duration of social interactions, covary as a set of tolerant traits in Shodoshima monkeys. This study suggests broad intraspecific variation of dominance style in Japanese macaques as can be seen in some other primate species.     

Sequential analysis of the social behavior of infants in groups of Japanese monkeys (Macaca fuscata fuscata)

We employed techniques of behavioral entropy to carry out a quantitative analysis of sequences of behavioral patterns evident in the interaction between infants and other members of a group of Japanese monkeys (Macaca fuscata fuscata). The group concerned included examples both of monkeys in captivity and in the wild state. The results were examined as a function of the animal age and environmental differences (cage-field). An example is given to illustrate the use of information theory. Findings partially confirmed that the variability of social behavior decreases as the age of the animals increases.     

Dihydrotestosterone propionate effects on dominance and sexual behaviors in gonadectomized male and female rhesus monkeys.

One triad of male and two triads of female gonadectomized rhesus monkeys were observed as social groups assembled for repeated hour-long sessions. Social relationships were measured in terms of aggressive behavior between the members of each group in order to determine the dominance hierarchical order. Sexual performance was assessed for each male, before and after castration, in tests with an estrogen-stimulated ovariectomized female. Similar measures were made when the same female was periodically introduced to the all-male triad. When dihydrotestosterone propionate (DHTP) was administered for a period of 6 weeks to the middle-ranking member of each group, social status changes occurred in two groups, one male and one female, resulting in the elevation of the treated monkeys to the highest rank in the dominance hierarchy. In the other female group, aggressive behavior was increased with DHTP treatment of the middle-ranking female. Somatic effects, particularly a gain in body weight, occurred in all treated animals. Yawning behavior also increased significantly in those animals receiving DHTP. The latter two effects returned toward pretreatment levels following the cessation of hormone injection; however, changes in dominance hierarchy persisted to the end of the experiment, 6 weeks following the last DHTP treatment.     

Social organization of captive monandrous squirrel monkey groups (Saimiri sciureus).

1 adult male and 4 adult female squirrel monkeys were observed together as a group, isolated from all other monkeys. 3 of the 4 females were deafened for a previous experiment. Deafening, however, had no apparent, permanent effect on social behavior. Social dominance hierarchy was evaluated in a variety of situations. The results were compared with those of a similar set of observations on the females prior to the introduction of the male. Before the male was introduced, the dyadic interactions involving food stealing, body grasping, and sexual behaviors were indicative of a female linear rank order. After the male was introduced, the rank order among the females generally remained intact, with the male becoming the highest ranking member in the group. The noteworthy exception to the stability involved the highest ranking female, whose position in the hierarchy was threatened. Heterosexual interactions predominated. Homosexual behavior was also observed, although appreciably reduced in frequency as compared to the all-female group situation. A similar rank order hierarchy was observed in a second group of squirrel monkeys comprised of 1 adult male and 4 adult females. None of these monkeys was deaf.     

The use of redirection in a captive group of Japanese monkeys

The present study was chiefly focused on nonadult animals of a captive group of Japanese monkeys housed at the Rome Zoo. Over a five month-period, during 1 hr daily observations, threats, chases, physical assaults, submissions, and flights showed by each participant to agonistic interactions were recorded. Sex differences in the behavioral responses to received aggression, in the distribution of threats or attacks in dyadic interactions and in the second dyads of redirections, in the dominance relationship between actor and target in dyadic interactions and in the second dyads of redirections, emerged. The results stressed the short term functional implications of redirection behavior and suggested more long term functional implications to be effective in the female redirection behavior.     

Effects of orbitofrontal lesions on social behavior in a confined group of stump-tail macaques (Macaca speciosa)

We grouped 14 stump-tail macques, five males and nine females, and observed social behavior before subjecting four of them to resection of orbitofrontal cortex. Four monkeys also received control lesions of superior temporal cortex and the remaining animals served as unoperated controls. Observations of social behavior continued after surgery on the following behavior: Joining, grooming, self-grooming, threat, aggression, and presenting (total hours of observation equaled 154). Monkeys with orbitofrontal lesions showed decreases in threat and aggression but only one such monkey fell in dominance. Control (operated and unoperated) monkeys displayed little change in these behaviors. Monkeys with orbitofrontal lesions also increased joining and self-grooming but showed a decrease in grooming of others. Presenting did not change. The role of orbitofrontal cortex in modulating different aspects of social interaction is emphasized by these results. However, in primates this area of the frontal lobes appears to have its major influence in the emotional loading of such complex behaviors.     

Squirrel monkey dominance and social behavior as related to group size and group structure

Adult male and female squirrel monkeys were tested in nonsocial adaptation and pairwise and triad social situations differing in sex composition. Social behaviors, nonsocial behaviors, and dominance hierarchies were observed during social testing. Dominance hierarchies were similar in groups differing in size and social structure. Nonsocial behaviors decreased in females and submissive animals paired with males or dominant monkeys. Aggressiveness between females decreased and the beginnings of coalitions between females were observed in the presence of a male. The social behavior patterns, but not dominance hierarchies, are consistent with behaviors observed in larger groups of squirrel monkeys.     

Effect of unknown relationships on linearity, steepness and rank ordering of dominance hierarchies: simulation studies based on data from wild monkeys

The presence of unknown dyadic relationships is a common problem in constructing dominance hierarchies for groups of social animals. Although previously acknowledged, the influence of unknown relationships on hierarchy measures like linearity and steepness has not been studied in detail. Using real data-sets from four groups of wild monkeys, we illustrate how unknown relationships affect linearity and steepness of hierarchies and the consistency of rank ordering based on de Vries’ I&SI method. Monte Carlo simulations revealed significant negative linear relationships between the proportion of unknown relationships and both linearity and steepness. These simulations over-estimated steepness and linearity indices relative to additional real-data input matrices. Rank orders became inconsistent at 26–38% unknown relationships, depending on the group. Group size and the specific input matrix substantially affected how much unknown relationships influenced steepness and linearity, the values of these indices and the point at which rank order became inconsistent. We recommend caution in characterizing the dominance structure of a group with many unknown relationships, and in drawing conclusions about hierarchy linearity and steepness based on few input matrices, especially if they contain many unknown relationships. Quantitative characterizations of hierarchies are perhaps best viewed as a somewhat fluid range rather than fixed values.     

Laboratory methods for the assessment of social dominance among captive squirrel monkeys

The utility of various techniques for assessing dominance relations within captive primate groups has been repeatedly debated. The present research compared status rankings derived from observations of spontaneous agonism with rankings based on success in experimental competitions within two groups of captiveSaimiri. Observation of social agonism revealed stable dyadic dominance relations in both groups. Status rankings derived from the competitive Water Dominance tests were neither temporally stable nor concordant with observational rankings. Thus the utility of the Water Dominance test as an index of dominance among captive squirrel monkeys seems questionable. Results are discussed in terms of ecological factors in group adaptation which lead to species-specific differences in the relationship between social conflict and competition.     

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.     

An ecological study of troop fissions of Japanese monkeys (Macaca fuscata yakui) on Yakushima Island,Japan

Wild, habituated, Japanese monkeys were observed from 1975 to 1979 on Yakushima Island, Southern Japan. The monkey troops had a continuous distribution in a warm temperate forest. Demographic data on local populations was collected. The population density was 33 animals/km². The growth rate of the studied troop was 3.0% per year. A significant correlation between home range areas (R) and troop size (P) was found (r=0.955,p<0.005), using anR-P equation,R=1.84P. One troop split into three troops through two successive fissions. Twenty-one intertroop encounters were observed. Five types of encounters were distinguished. The encounters were apparently territorial defence. Increases in birth rate and socionomic sex ratio after the fissions were prominent. The following four factors had a direct effect upon the dispersion of the troops after fission: (1) dominance relation between the fission troops; (2) social pressure of the neighbors; (3) troop's attachment to its home range; and (4) structure of the environment. The home range of Japanese monkeys is a territory, and territoriality is a population regulating mechanism which serves to reduce competition for food.     

The influence of rank on affect perception by pigtailed macaques (Macaca nemestrina)

Previous studies of affect perception in nonhuman primates have involved young animals and/or manipulations of early experience. Based upon data suggesting that middle-ranked monkeys in small social groups show patterns of behavior different from their low- or high-ranked counterparts, the current study examined the role of social rank in affect perception by normally reared, adult female pigtailed macaques. Employing color videotapes as the presentation medium, we observed animals as they watched unfamiliar animals display social (aggressive or submissive) or nonsocial behavior. Virtually all threats were recorded as the subjects watched the submissive presentations, and most submissive signals occurred while watching aggressive behavior tapes. Middle-ranked monkeys were most attentive during all presentations, and levels of disturbance behavior were related to rank of the watcher and type of presentation observed. The results suggest that dominance status is an influence in the process of affect perception.     

Social organization and social behavior in two subspecies of squirrel monkeys (Saimiri sciureus).

Social organization and social behavior were examined in two subspecies of squirrel monkeys which differ markedly in the degree of sexual dimorphism. The Bolivian squirrel monkeys, the subspecies with greater sexual dimorphism, manifested a sexually segregated form of social organization, while the social organization of the Guyanese monkeys was sexually integrated. Dominance relationships were found to reflect these patterns of sexual segregation or integration; in the Bolivian social groups separate linear dominance hierarchies were established within each sex while the Guyanese monkeys established a single linear hierarchy which included both males and females. Relationships between males and females in the two subspecies appear to be regulated by two distinct mechanisms, dominance in the Guyanese monkeys and sexual segregation in the Bolivians.     

A Novel Method of Assessing Dominance Hierarchies Shows Nuance,Linearity and Stability in the Dinosaur Ant Dinoponera quadriceps

Many social species with relatively simple societies have dominance hierarchies of individuals, with dominant individuals achieving fitness and subordinate individuals either queuing to obtain fitness or achieving only indirect fitness by helping relatives. Assessing the dominance hierarchy in a social group is generally based upon observing dyadic interactions as and when they occur spontaneously within the whole‐group setting. However, this method can be very time‐consuming because many dyads interact only very rarely, necessitating either extremely long observation periods or many dyadic relationships being unresolved. Here, we report an alternative method using the queenless dinosaur ant Dinoponera quadriceps, which lives in colonies containing tens of individuals. We removed all individuals from their nest and observed the dominance behaviours expressed in isolated dyadic interactions for every pairwise combination of individuals. Individuals showed a classic dominance behaviour in this setting, and the rapid nature of the assay allowed us to observe every dyadic relationship on a weekly basis over 4 weeks. The dominance hierarchies based on these isolated dyadic interactions correlated well with those produced by the conventional method of colony observations. They showed the hierarchies to be highly linear and stable, and also revealed that dominance relationships may extend further down the hierarchy than previously thought. Although highly manipulative, the isolated dyadic interaction method works well and will likely make more feasible the study of other social species in which pairs of individuals can be isolated together.     

Mirror guided behavior in Japanese monkeys (Macaca fuscata fuscata)

Two male Japanese monkeys were trained to use a mirror to reach an object that could not be seen directly. Training to use a mirror in this way proceeded, step-by-step, from reaching a piece of apple to key-tracking. In Experiment 1 the monkeys were trained to use the mirror to locate a desired object, a piece of apple in a box facing the mirror, which could be seen only by looking into the mirror. The apple, once located, however, could be grasped without further reference to the mirror. This behavior is referred to as mirror mediated object discrimination. In subsequent experiments the monkeys could not reach the goal object except by observing it and his hand movement in the mirror. In Experiment 2 the target was a piece of apple visible in the mirror, in Experiment 3 an illuminated key and in Experiment 4 a series of keys which were illuminated sequentially. Mirror guided behavior such as shown in Experiment 2, 3, and 4 has not previously been demonstrated in monkeys.     

The role of play in social organization: Comparative observations on squirrel monkeys (Saimiri)

Various functional theories of play stress that social play is essential for the practice and learning of sex roles, dominance relationships, troop culture, integration of individuals into the troop structure, the control of aggression, etc. Data on squirrel monkeys (Saimiri) in natural environments indicate that social interaction and troop integration can develop in various manners in the absence of social play.Comparative observations were made on squirrel monkeys in a seminatural environment in Florida and 43 natural environments in Panama, Colombia, Peru, and Brazil. There was a broad range of variance in the data on ecology, troop size, troop cohesiveness, average individual distances, frequency of play, etc. In some environments, individuals in the infant and juvenile age classes engaged in social play for approximately 1.5 to 3 hours a day. However, in one environment, not a single incidence of social play occurred during 261 hours of close range observation. The troops in which no play occurred were very cohesive (i.e., they seldom fragmented), and the animals traveled at close individual distances. Agonistic interactions were not uncontrolled. Copulations were observed; and 85 percent of the adult females were accompanied by infants, which indicates a normal rate of reproductive success for the species.Data are presented on friendly, aggressive, sexual, and spacing behavior in squirrel monkeys. These data indicate that (1) social play is not necessary for the development and/or learning of an adaptive modicum of social interaction patterns and troop cohesion, but (2) the opportunity to play provides learning experiences in which young animals can develop more complex, varied social interaction patterns and stronger habits for engaging in frequent social exchanges.     

Proximity structure in a captive colony of Japanese monkeys (Macaca fuscata fuscata): An application of multidimensional scaling

Spatial proximity was used to investigate the social structure of a group of 14 Japanese macaques (Macaca fuscata fuscata) living in Cavriglia Park (Arezzo, Italy). Instantaneous sampling was used to collect data. From April 1984 to March 1985, 273 hr of observation were accumulated. Time spent in proximity by any two monkeys was transformed into a similarity index. Two triangular matrices were created with these indices (one for the non-breeding and the other for the breeding season) and submitted to nonmetric multidimensional scaling (MDS). During the non-breeding season proximity proved closely related to hierarchical relationships and the existence of two real social classes was suggested. Tendency to loneliness was associated in this period with old age in females and low rank in both females and males. Moreover, socially stable versus socially unstable animals had different spacing patterns. Almost the same central-peripheral structure was outlined in both seasons, consistently with a stableoikia hypothesis for this group under these conditions. During the breeding season social organization was influenced by individual sexual interest. A male spacing pattern emerged, probably in correlation with female homosexuality, which played a preeminent role in the sexual context. The relative loneliness of sexually immature individuals was evident in this season.     

Asymmetry and Dimensions of Relationship Quality in the Japanese Macaque (<Emphasis Type="Italic">Macaca fuscata yakui</Emphasis>)

Cords and Aureli (2000) proposed that relationship quality can be described by three components, i.e., value, security, and compatibility, based on the benefits social partners receive from their relationship and on how likely it is for them to maintain a stable friendly relationship over time. We aimed to examine whether this 3-components structure can describe social relationships and to investigate the degree of asymmetry of social relationships. We used the Japanese macaque as our model species, as group members may form strong social relationships with one another. We collected 359.2 h of focal samples, on 21 monkeys, and ran a principal component analysis (PCA) on dyadic scores for 9 variables measuring social relationships, e.g., grooming or aggression. This PCA gave 3 components. However, a second PCA run on scores per individual, i.e. for each variable and dyad we obtained 1 score for the actor and 1 for the receiver of behavior, gave a 5-component structure. We interpreted this result as evidence of the asymmetric nature of social relationships, in terms of the frequency and type of behavior exchanged between social partners, in the Japanese macaque. This interpretation was confirmed by the low correlation coefficients between behaviors given and received within a dyad. Overall these results provide mixed support for the 3-components structure predicted by Cords and Aureli (2000). They also show that social relationships may be largely asymmetric and that this asymmetry should be considered in studies on social behavior.