Effects of rearing on aggression and subordination in papio monkeys

The objective of this study is to assess the effects of short-term maternal deprivation (birth to 12 weeks) followed by peer group rearing on the development of aggressive and subordinate behaviors in papio monkeys (superspecies – Papio cynocephalus). Nursery reared monkeys (34 males and 30 females) were compared with mother-peer reared monkeys (11 males and 12 females) in late infancy (6 to 12 months of age) and at the end of their juvenile stage (36 to 42 months of age) in social groups composed of 75% nursery reared subjects and 25% mother reared subjects. Focal animal data were analyzed with a repeated measure ANOVA model. In general, the nursery reared infants tended to be less aggressive than mother-peer reared infants and performed less dominance behaviors, such as displace. Significant sex differences were present in the performance of aggressive (♂ > ♀) and subordinate (♂ > ♀) behaviors. Significant age differences were observed, with infants having consistently higher rates of performance.     

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.     

The ontogeny of sex differences in the behavior of patas monkeys

Many studies of sex differences in primates have been based on small experimental groups of peers in which only a limited range of social behavior could be expressed. In addition, the first few months of life are often the focus of such studies, with relatively little attention paid to older juveniles. In this study, 11 male and 9 female juvenile patas monkeys, living in a captive social group with all age-sex classes available, were observed between 1 and 4 years of age. A subset of seven patas monkeys was also observed between birth and 1 year of age. Here, we report the development of sex differences in independence, play, grooming, positioning behavior, and aggression over the juvenile period. Juvenile male patas monkeys played more and in longer bouts than females, but wrestling (rough-and-tumble play) was not more common among males. There were few differences in behaviors directed to male and female juveniles by other group members. Distinct differences emerged only in the behaviors of the juveniles themselves, with females being more active participants in social and aggressive interactions than males. In general, sex differences in patas monkeys show a mixture of patterns, some of which are predictive of adult sex differences and some of which appear to be specific to the particular demands of the juvenile period in this species     

Rearing condition and plasma cortisol in rhesus monkey infants

Previous studies comparing plasma cortisol levels in mother-reared and nursery-reared rhesus monkey infants under baseline and stress conditions have reported conflicting findings. Differences in subject age, procedures, and specific rearing history may account for many of the discrepant findings. In the present study, mother-reared infants from large social groups, peer-only reared animals, and infants reared with surrogates and limited peer contact were studied in different test conditions across the first 6 months of life. Infants were sampled under three conditions: following a neonatal assessment at Days 14 and 30, immediately upon capture on Day 60, and after 30-min isolation periods on Days 90, 120, and 150. Mother-reared infants exhibited higher cortisol levels on Days 14 and 30 than did both types of nursery-reared infants. In addition, Day 60 basal values of mother-reared infants were higher than those of both peer-reared and surrogate/peer-reared infants. However, on Days 90, 120, and 150, both mother-reared and peer-reared infants exhibited higher cortisol levels in response to separation and 30-min isolation than did the surrogate/peer-reared infants. These differences may reflect group-specific variations in physical environment, capture time, feeding regimen, or diurnal HPA axis rhythms. Am. J. Primatol. 46:311–321, 1998. © 1998 Wiley-Liss, Inc.     

Early behavioral development and temperamental traits in mother- vs peer-reared rhesus monkeys

Behavioral characteristics (“traits”) of 24 mother-reared and 24 nursery/peer-reared rhesus monkey infants were assessed via rating scales from the third through the seventh month of life while housed with their rearing partners, and from months 8–10 after all animals had been placed in novel peer groups. The animals were also tested at 8 months of age on the Bayley Scales of Infant Development adapted for nonhuman primates. During the early period effects noted were primarily developmental. Peer-reared animals were rated as increasingly less cautious and more attentive to the outside environment over time, while mother-reared infants declined in ratings of dependence on their mothers. All animals were rated as increasingly active and excitable, and less fearful, over time. For the period of months 8–10, peer-reared animals showed higher confidence ratings in month 10, and all animals showed a decline in attachment to cagemates. Mother-reared animals showed more hostility to the examiner during Bayley testing, whereas peer-reared animals showed more fear. Sex effects included greater ratings for independence from mothers, greater activity over both the early and later periods, greater excitability, greater attentiveness to the extra-cage environment, less cautiousness, and better performance on one Bayley problem for females.     

Infant stumptailed macaques reared with mirrors or peers: Social responsiveness,attachment, and adjustment

Comparisons of activity toward mirrors and peers in infant macaques being reared with one of these stimuli as the primary rearing partner revealed markedly greater social responsiveness to a fully accessible cagemate than to one's own reflection. Measures of exploration, aggression, and especially play all revealed the cagemate to be the more potent social stimulus. Mirror-reared infants given additional experience of a live peer behind a transparent partition were less responsive to the mirror than were infants with no social stimulation other than a mirror. In contrast, cagemate-directed behavior of peer-reared infants was not seriously affected by additional exposure to a mirror. A fully accessible peer also elicited more social responding than a peer behind a transparent partition, and infants with experience of both a live cagemate and mirrors were generally more responsive toward the former. Greater agitation in peer-reared than in mirror-reared stumptailed monkeys during separations from their rearing partners suggests that exposure to the physically accessible partner led to stronger attachments. Infants reacted positively to a moderately unfamiliar environment but showed behavioral disruption when placed in a very unfamiliar environment. Disruption was especially evident in peer-reared infants, in which exposure to the unfamiliar environment was compounded with the absence of the attachment figure. Mirror-rearing appeared to reduce the tendency toward ‘isolation syndrome’ behaviors compared to alone-rearing, and these behaviors appear to be less common in stumptailed than in rhesus macaques.     

Hunting strategies in wild common marmosets are prey and age dependent

We investigated the hunting strategies of wild common marmosets (Callithrix jacchus) to determine whether the strategies differed among animals of different age classes and/or prey type. The study was conducted in a fragment of Atlantic Rain Forest, situated 40 km from Recife (PE/Brazil). Twenty‐seven individuals from four social groups were observed. Captured prey items were divided into three categories. The hunting strategies of the common marmosets were ranked into four categories. The acquisition of larger prey (items more than 2.0 cm) involved the appropriate body movements and postures that concealed the approaching marmosets, whereas the acquisition of smaller prey (items under 2.0 cm) involved less concealing behaviors. Furthermore, adults and juveniles (age ≥5 months) were more capable of capturing larger prey than were younger (1–2 months) or older infants (3–4 months). Although older infants were successful in capturing certain prey, they often failed when they attempted to capture larger prey that jumped and/or used flight to escape. The results suggest that both the experience of the monkeys and escape behavior of the prey affect predation efficiency in wild common marmosets. Am. J. Primatol. 72:1039–1046, 2010. © 2010 Wiley‐Liss, Inc.     

The effects of rearing method on social behaviors of mentored,captive‐reared juvenile California condors

Puppet‐reared and parent‐reared captive‐bred California condor (Gymnogyps californianus) juveniles were studied before their release into the wild. Behavioral data were collected during social interactions within two cohorts of juveniles (N = 11) and their adult mentors (N = 5). The purposes of this study were to (1) document the social behaviors of mentored juvenile California condors, and (2) compare social behaviors for two different rearing methods (puppet‐reared versus parent‐reared) during two phases of the mentoring process (San Diego Wild Animal Park versus release sites). Of the 17 behaviors examined by 2 × 2 analyses of variance (ANOVAs), two significant interactions between the rearing method and mentoring phase were found: pulls feathers and feeds alone. For both behaviors, parent‐reared condors engaged in these activities more often at the zoo and less often at the release pens than did the puppet‐reared condors. The main effect of rearing was also significant for two behaviors: near others, and receives contact aggression from other. Parent‐reared birds were more likely to be near another bird and receive contact aggression, regardless of mentoring phase, than puppet‐reared birds. The effect size for 16 of the 17 behaviors was greater for the rearing method than for mentoring phase. Rearing method differences may persist long‐term, as parent‐reared adult mentors were significantly more aggressive than puppet‐reared adult mentors. Dominance relations were examined for both cohorts, with the first cohort exhibiting a strong linear relationship (h′ = 0.86, P = 0.018), whereas the second cohort exhibited a moderate but non‐significant linear hierarchy (h′ = 0.63, P = 0.21). The rearing method had no effect on dominance among the juveniles, but adults were probably dominant to juveniles (P = 0.052; the difference was nearly significant). Although social behaviors between the two rearing groups were similar in most respects, this study is the first to document measurable differences between puppet‐ and parent‐reared captive‐bred California condor juveniles. Zoo Biol 27:1–18, 2008. © 2007 Wiley‐Liss, Inc.     

Mirror reactions in a zoo colony of Cebus monkeys

The extensive research investigating the reactions of a number of species of nonhuman primates to their mirror images has revealed that monkeys have never been observed to react with self-directed behaviors, as have some species of higher apes. The intermittent exposure of captive Cebus monkeys to a mirror over a 5-week period produced species-specific social reactions to the mirror, supporting the suggestion that at least in some instances the monkeys were viewing their mirror image as a conspecific. The variability in the duration and expression of mirror-directed behaviors observed in the study appeared to be related to the age and past experience of the monkeys. The duration of mirror viewing of subadults was over twice that of the adults, while the young, hand-reared animals exhibited more manipulative and fewer social behaviors than did the young animals raised in the zoo. The average viewing time of the zoo colony decreased substantially over the course of the study but the monkeys were still spending an appreciable time at the mirror after 5 weeks.     

Persistent Effects of Peer Rearing on Abnormal and Species-Appropriate Activities but Not Social Behavior in Group-Housed Rhesus Macaques (Macaca mulatta)

Nursery rearing of rhesus macaques (Macaca mulatta) alters behaviors but may be necessitated by maternal rejection or death, for research protocols, or for derivation of SPF colonies. The Tulane National Primate Research Center maintains a nursery-reared colony that is free from 9 pathogens as well as a mother-reared colony free from 4 pathogens, thus affording an opportunity to assess the outcomes of differential rearing. Nursery-reared macaques had continuous contact with 2 peers and an artificial surrogate (peer rearing). Focal sampling (432 h) was collected on the behavior of 32 peer-reared and 40 mother-reared subjects (age, 1 to 10 y; immature group, younger than 4 y; adult group 4 y or older). All animals were housed outdoors in like-reared social groups of 3 to 8 macaques. Contrary to expectation, no rearing effects on affiliative or agonistic social behaviors were detected. Compared with mother-reared subjects, peer-reared macaques in both age classes had elevated levels of abnormal appetitive, abnormal self-directed, and eating behaviors and lower levels of locomoting and vigilance (highly alert to activities in surrounding environment); a trend toward reduced foraging was detected. Immature but not adult peer-reared monkeys demonstrated more enrichment-directed behavior and drinking and a trend toward more anxiety-related behavior and inactivity. No new rearing effects were detected in adults that had not been detected in immature subjects. Results suggest that modern peer-rearing practices may not result in inevitable perturbations in aggressive, rank-related, sexual, and emotional behavior. However, abnormal behaviors may be lifelong issues once they appear.Abbreviations: MR, mother reared; PR, peer rearedRearing history is an important consideration when addressing the needs of macaques in captivity. In breeding colonies, nursery rearing may be a necessary management intervention due to maternal incompetence or death and when a foster dam cannot be identified. In addition, nursery rearing may be required for specific types of research. Decades of research broadly indicate that a combination of an artificial surrogate, human interaction, and social contact with peers is the best way to rear macaques in the nursery, a strategy that will avoid the devastating effects of total-isolation rearing^12,19,20 and allow the animals to successfully integrate into and breed in larger social groups.³⁴ However, even with modern nursery-rearing practices, the behavioral and physiologic profiles of nursery-reared macaques differ from those of macaques that have been raised with their mothers in a social group. Behaviorally, nursery rearing is associated with an increased risk for developing repetitive stereotypies, self-biting, self-wounding, and noninjurious self-directed abnormal behavior.^{3,10,16,30,31,35,41} In addition, some evidence suggests that nursery rearing results in heightened anxiety^13,21,42 and lower levels of environmental exploration.⁶ With regard to social behavior, nursery-reared macaques show decreased levels of grooming, play, and social reciprocity, and the presence of companions does not appear to buffer them from stress.^26,42 In addition, nursery rearing is associated with increased fear and aggression.^27,44 Sexual and maternal deficits may occur as well.^15,17,18,38In addition to effects on behavior, physiologic changes have been identified in macaques reared in the nursery setting. Differential rearing affects brain architecture involved in cognition,³⁷ emotional processing²⁵ and vulnerability to adverse effects of stress.⁴⁰ Although evidence concerning rearing effects on the hypothalamic–pituitary–adrenal axis is equivocal, differences including reduced levels of oxytocin, norepinephrine, and homovanillic acid in the cerebrospinal fluid have been reported.^22,27,28,44 Studies have identified several indicators of immune system alterations in nursery-reared macaques, such as decreased proportions of cytotoxic and suppressor T cells, reduced natural killer cell activity, and increased lymphocyte proliferation.^9,29With regard to social management in the nursery, strategies fall into 2 main categories: peer rearing, involves continuous cohousing, whereas surrogate–peer rearing involves brief periods of cohousing of otherwise singly housed infants. Although infants in both rearing conditions may be provided an inanimate surrogate, surrogate–peer-reared infants are housed for the majority of the time with the inanimate surrogate only, with the intention that infants’ need for clinging to an attachment figure will be directed toward the surrogate, even when peers are present. However, this distinction is generalized, and both nursery-rearing categories may involve variations across facilities. Moreover, a subset of the literature differentiates between these housing conditions and compares them. In comparison with surrogate–peer rearing, peer rearing is associated with lower levels of stereotypic and self-injurious behavior, ^31,35,36 whereas surrogate-peer rearing appears to mitigate the increased anxiety observed in peer-reared subjects.^12,20,40 In addition, surrogate–peer-reared macaques show less social clinging, fear, and aggression and more exploration and play than do their peer-reared counterparts.^5,7,35,36Although the literature on the nursery rearing of macaques is extensive, many of the studies concerning the behavioral effects of rearing involve both infants and older subadults or evaluations of behavior indoors and under test conditions. Therefore these populations need to be characterized more thoroughly under the conditions in which they are housed. The relative costs and benefits of the 2 forms of nursery rearing may vary with time and housing condition, especially when the ultimate goal is to maintain the animals long-term and for breeding purposes. For example, nursery-reared macaques may be eventually housed in small outdoor groups, particularly as part of the process of deriving SPF colonies,³⁸ and the literature in the context of their behavior in a more naturalistic group setting is sparse.The question of which nursery rearing practice optimally equips macaques with species-normative behaviors to live in an outdoor group-housed situation is best assessed by comparing mother-reared, peer-reared, and surrogate–peer-reared subjects in similar physical and social conditions. However, even when all 3 categories of animals are unavailable, comparing mother-reared with peer-reared macaques is valuable for assessing the downstream consequences of nursery-management decisions. The objective of the current study was to characterize the behavior of peer-reared, outdoor group-housed rhesus macaques compared with that of mother-reared, outdoor group-housed subjects. Although we expect broad social and reproductive competence in these animals, we test the prediction that peer rearing results in significant perturbations in social behavior as well as heightened anxiety. Characterizing this population is necessary for determining its behavioral needs. If the long-term effects of rearing mimic signs of current reduced wellbeing, it is difficult to assess the need for intervention and the expected response to that intervention. This assessment will allow us to measure the cost of management decisions designed to mitigate rearing-related abnormal behaviors, to predict or interpret the behavior of breeding groups consisting of peer-reared macaques, and ultimately, to contribute to the literature that may guide our ability to make evidence-based decisions regarding different nursery-rearing strategies. Furthermore, this study uses subjects of widely varied ages in both rearing categories to gain information on the long-term stability of rearing differences with increasing age.     

Pair-rearing infant monkeys (Macaca nemestrina) using a “rotating-peer” strategy

Appropriate rearing conditions for captive primates are important for both research and breeding purposes. In an earlier study, pigtailed macaque infants that were pair-reared with a single continuous partner exhibited excessive social clinging and could not adapt to living in large social groups at 8–10 months of age. In the present study, eight macaques were pair-reared until they were 6 months old. Each member of an animal's four-monkey social group served as a home-cage partner. In an attempt to reduce excessive mutual clinging, the pairs were rotated every 2–3 days to increase the variability of social stimulation in the home cage. However, these infants developed abnormal social behaviors that were in some cases even more extreme than those exhibited by infants pair-reared with a single continuous partner. A second goal of this experiment was to study interlaboratory reliability for the development of social behavior. The animals were divided into two groups, one housed in a nursery and the other in a biological safety level 3 virus laboratory. Some differences were detected between the two groups, demonstrating the necessity of controls in biobehavioral developmental research. Am. J. Primatol. 41:141–149, 1997. © 1997 Wiley-Liss, Inc.     

Peer separation in infant chimpanzees,a pilot study

Seven nursery reared chimpanzees (Pan troglodytes), 7.5 to 10.5 months of age, were studied to determine the effects of a short period of separation from their peers on behavior and heart rate. The chimpanzees were separated from their mothers at birth, and reared in the nursery in a group living environment. The experiment encompassed a 13-day period, including 4 days of normative baseline, 5 days during which three of the infants were separated and housed in isolation while the other four controls remained together, and 4 days in which all of the animals were reunited. Six quantified behavioral observations and five heart rate measurements were obtained daily. Following separation, the isolated infants were behaviorally agitated, and exhibited increases in vocalizations, rocking and self-clasp behaviors, as well as changes in facial expression including cry face, whimper face and pout face. Time spent locomoting decreased in all seven animals during the separation period. Agitated behavior in the separated and isolated infants alternated with stationary withdrawn behavior. Individual differences were prominent. Heart rate was notable by the generally poorly developed circadian rhythmicity throughout the 13 day period; significant HR changes did not appear otherwise associated with separation. Day three of separation appeared to represent a point of transition with stereotyped motor behaviors developing in the three isolated infants and in one control infant.     

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.     

Playmate relationships among individuals of the Japanese monkey troop in arashiyama

Observations of play behavior were made on a troop of Japanese monkeys for five months. The troop consisted of 125 animals during the study period. Only 104 animals were observed playing with the troop members while the other 21 animals were never observed playing with other individuals. Two-member play was the most frequent. On the average, a monkey played with 20.7 individuals. A total of 6,068 play bouts were observed. The frequency of play appeared to be affected by age, sex, and degree of relatedness. One-year-old infant males played most with other members and the frequency of play decreased with age. Between monkeys whose disparity of age was less than two years, 5,763 bouts (95.0% of the total) were observed. Moreover, among sameaged monkeys who comprised 10.6% of the possible pair combinations, 2,739 play bouts (45.1%) were observed. Juvenile males played with same-sexed peers more than with opposite-sexed peers, whereas older juvenile females appeared to play with infants of both sexes. Individuals who were related and similarly-ranked tended to play together. There was no apparent preference for animals to play with the offspring of the highest-ranking female. Dominance rank of infnats and juveniles was primarily affected by rank of their mothers and to a lesser extent by play partners. Dominance rank of older juvenile males is more likely to be affected by play partners than females. It may be a critical time for males when they leave their natal troop and join a new troop. The timing of troop shifting by males seemed to be affected by the presence or absence of play-mates. For male Japanese monkeys, play is very important in developing social bonds. Play may act to perpetuate social bonds, enhance the chance of survival, and may contribute to their future reproductive success.     

The development of white adipose tissue. Effect of litter size on the lipoprotein lipase activity of four adipose-tissue depots, serum immunoreactive insulin and tissue cellularity during the first year of life in male and female rats.

(1.) Male and female rats reared in litters of four gained body weight more rapidly than animals reared in litters of 16. The differences were more marked in males than females and became less marked in both sexes with advancing age. (2.) The relative weights of the perigenital, perirenal, subcutaneous and intramuscular white-adipose-tissue sites in the animals from small litters indicated their relative obesity compared with animals from large litters. A sex-related difference in the distribution of adipose tissue between the four sites was seen in animals reared in litters of both four and 16. (3.) Although at 30 days of age all the animals had more numerous and larger fat-cells in their white-adipose-tissue depots than animals reared in large litters, the pattern of change thereafter was both site- and sex-specific. During the post-weaning period (30-300 days), although detailed differences were apparent between sites, a general pattern of increased cell size in males and increased cell numbers in females emerged as being the important determinants responsible for the differences in depot sizes seen when animals from litters of four and 16 were compared. (4.) Lipoprotein lipase activities, expressed as units/g fresh wt. of tissue, in the depots of animals reared in groups of four were unaltered compared with those reared in groups of sixteen during the post-weaning period (47-300 days of age), and enzyme activities expressed per depot merely reflected differences in tissue weights. (5.) Lipoprotein lipase activities per 10(6) cells were higher in males reared in fours compared with those reared in sixteens of equivalent age, but were unaltered for females. (6.) The persistent hyperinsulinaemia of animals reared in litters of four is discussed in relation to the observed differences in enzyme activity and white-adipose-tissue cellularity.     

Intimate social behavior in infant interactions in Cebus apella

The development and individual stability of three intimate social behaviors (Lipsmacking, Carrying Attempts, and Facial Inspection) were examined for 43 group-housed Cebus apella infants from birth to 2 years of age. Occurrence of these behaviors was scored from 10-min videotape samples recorded three times a week over that time. Frequency of Lipsmacking and Carrying Attempts by adult males, adult females, and juveniles were all highest in early months and decreased to low levels by the end of the first year. Facial Inspection of partners by infants, in contrast, first began at 3-4 months and increased over time, at least to adult males and juveniles. Correlational analyses indicated stable individual differences in these interactions with infants and outlined a relationship between these intimate behaviors and more general social patterns reported previously for these animals. Results suggest that adult males may play a special role in affording juveniles opportunities for social learning of foraging and manipulative skills.     

Social context and reaction to separation in peer-reared pigtail macaques: Some preliminary observations

The social environment affects both behavioral and physiological responses to separation from the mother. Less information is available on the impact of the social environment on the response to separation in peer-reared infant monkeys. This study reports the responses of peer-reared pigtail macaque infants to repeated separations, and the impact of social versus isolation housing during the separation. The responses of two pairs of monkeys were studied during four three-day separations. One of each pair was housed in isolation during the separation, and the other was with another pair of peers, with whom they had been living for one month prior to the separation. The isolation-housed peer responded to the separation with behavioral agitation, but no depression. The socially-housed peer's behavior did not differ from baseline during the separation. During successive reunions, all the separated monkeys, regardless of housing condition, exhibited declining levels of behaviors related to maintaining proximity to their attachment figure. Although the number of subjects is small, the results suggest that the presence of social support, in the form of a familiar peer, can ameliorate the response to separation, and that with repeated separations the responses of the monkeys changes significantly.     

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.