Effects of Tourist and Researcher Presence on Fecal Glucocorticoid Metabolite Levels in Wild, Habituated Sulawesi Crested Macaques (Macaca nigra)

Ecotourism managers and researchers often assume that apparently habituated primate groups no longer experience adverse consequences of prolonged exposure to tourists or researchers. We examined the effects of tourists and researchers on fecal glucocorticoid metabolite output (FGCM) in three critically endangered, wild crested macaque (Macaca nigra) groups in Tangkoko Nature Reserve, Sulawesi, Indonesia. We assayed FGCM from 456 fecal samples collected from thirty-three adults. Tourists can walk through and among macaque groups freely. Hence, we examined the possible effects of tourists both (1) in the reserve when away and not interacting with the study groups and (2) when they were present within the macaque groups. Generalized Linear Mixed Model (GLMM) analysis indicated that when tourists were present in the forest, but not directly among the macaques, FGCM levels in the macaque tourism groups were higher in months with more tourists. When tourists were among the macaque groups, some female macaques experienced rises and subsequent postexposure decreases in FGCM levels, consistent with predictions for acute stress. Male FGCM levels increased with tourist numbers within the group. Nevertheless, they were not significantly different from levels during undisturbed or postexposure conditions. FGCM responses related to researchers in groups varied by group, sex, and tourist presence. However, the temporal patterning of FGCM responses showed little evidence of chronic stress from tourism at this site.

Cortisol metabolites vary with environmental conditions, predation risk, and human shields in a wild primate, Cercopithecus albogularis

Environmental challenges are often associated with physiological changes in wildlife that allow animals to maintain homeostasis. Among these, scarcity in resources, and risks from predators, competitors, and humans can all result in psychological and physiological stress. Yet, for habituated species, it is not clear whether this relationship with humans still holds to a lesser degree or is outweighed by the benefits of human presence - such as serving as a buffer from competitors or predators. We investigated how human presence and environmental challenges such as resource availability, weather, predation, and competition may be associated with variation in fecal cortisol metabolite levels (FCMs) in a group of samango monkeys (Cercopithecus albogularis) in the Soutpansberg Mountains, South Africa. FCMs can often broadly track environmental challenges and perturbations. Initially, we employed an exploratory analysis comparing candidate models representing biological hypotheses and found that those incorporating information on human presence had less weight than models for food availability, thermoregulation, and water scarcity. When we examined a subset of the data that included information on intergroup competition and predator alarm calls, we found that FCMs were higher on the day following potential predator encounters but not competitive interactions. As observer numbers increased, responses to predators flattened, indicating that the presence of several humans might deter predators and/or affect samangos' perception of danger - yet we could not distinguish between these possibilities. Together, these results suggest that ecological perturbations track with FCMs in this study population and challenge long-held assumptions that human presence has negligible effects on habituated study animals.

Monkey business: A girl's once strange dream

For close to 50 years, my research has focused on social relationships and social structure, particularly in macaques, and has been marked by a gradual broadening of scope. Supported by open-minded parents, I followed a once unconventional path into field primatology largely by ignoring distinct gender-based ideas about appropriate occupations for women that were prevalent when I was a child. Later, as Robert Hinde’s PhD advisee, I benefited enormously from his mentoring and from the transformative experience he provided. I began by examining infant social development in free-ranging rhesus monkeys and the integration of infants into the kinship and dominance structures of their groups. I gradually branched out to look at (1) kinship and dominance in additional age classes and macaque species, (2) additional aspects of social structure (reciprocity, agonistic support, tolerance, cooperation, conflict management), (3) mechanisms and organizing principles (e.g., attraction to kin and high rank, intergenerational transmission, demography, reciprocity, social style, time constraints) and (4) evolutionary underpinnings of social relationships and structure (e.g., parental investment, kin selection, socioecology, phylogeny, biological markets). For much of this journey, I have been accompanied by talented PhD students who have enriched my experience and whom I am now proud to call colleagues and friends. It is gratifying to realize that my career choice is no longer considered as unconventional as it once was.

Female preferences for male golden snub-nosed monkeys vary with male age and social context

Age is a key factor affecting sexual selection, as many physical and social traits are age-related. Although studies of primate mate choice often consider particular age-related traits, few consider the collective effects of male age. We tested the hypothesis that female golden snub-nosed monkeys Rhinopithecus roxellana prefer prime aged males (10–15 years) over younger and older males. We examined a habituated, provisioned troop during a 3-year study in the Qinling Mountains, China. Prime age males were more likely to be resident males of 1-male units (OMUs) than males of other ages. Since females are free to transfer between OMUs, the number of females per OMU can be indicative of female preferences. We examined the number of females per OMU, and found that it increased with resident male age up to 7–8 years, and declined after 12 years, such that prime age resident males had more females than other resident males. Females also initiated extra-unit copulations with high-ranking prime age males at significantly higher rates than with other males. Nevertheless, females tended to transfer from OMUs with high-ranking, older resident males to those with low-ranking, younger resident males. Thus, females appear to use different strategies when choosing social mates and extra-unit mates (i.e., different social contexts). We speculate that females may perceive early signs of aging in males and trade off the benefits and costs of high rank versus male senescence. This study lays the groundwork for future studies that examine possible direct and indirect benefits of such strategies.

Anthropogenic influences on primate antipredator behavior and implications for research and conservation

Predation risk affects prey species' behavior, even in the absence of a direct threat, but human-induced environmental change may disturb ecologically significant predator-prey interactions. Here, we propose various ways in which knowledge of antipredator tactics, behavioral risk effects, and primate-predator interactions could assist in identifying human-caused disruption to natural systems. Using behavior to evaluate primate responses to the ongoing environmental change should be a potentially effective way to make species conservation more predictive by identifying issues before a more dramatic population declines. A key challenge here is that studies of predation on primates often use data collected via direct observations of habituated animals and human presence can deter carnivores and influence subjects' perception of risk. Hence, we also review various indirect data collection methods to evaluate their effectiveness in identifying where environmental change threatens wild species, while also minimizing observer bias.

Time matching between grooming partners: Do methodological distinctions between short versus long-term reciprocation matter?

Primatologists have long focused on grooming exchanges to examine aspects of social relationships, co-operation, and social cognition. One particular interest is the extent to which reciprocating grooming partners time match, and the time frame over which they do so. Conclusions about time matching vary across species. Generally, researchers focus on the duration of pauses between grooming episodes that involve a switch in partner roles and choose a cut-off point to distinguish short from longer-term reciprocation. Problematically, researchers have made inconsistent choices about cut-offs. Such methodological variations are potentially concerning, as it is unclear whether inconsistent conclusions about short-term time matching are attributable to species/ecological differences, or are due in part to methodological inconsistency. We ask whether various criteria for separating short versus long-term reciprocation influence conclusions about short-term time matching using data from free-ranging rhesus ( Macaca mulatta) and captive-crested macaques ( Macaca nigra). We compare several commonly used cut-offs to ones generated by the currently preferred approach-survival analysis. Crested macaques displayed a mild degree of time matching regardless of the cutoff used. For rhesus macaques, whereas most cut-offs yielded similar degrees of time matching as the one derived from survival analysis, very short ones significantly underestimated both the degree of time matching and the influence of rank distance on time matching. Although researchers may have some flexibility in their choice of cut-offs, we suggest that they employ caution by using survival analysis when possible, and when not possible, by avoiding very short time windows.

Infant Handling Among Primates

Primates, particularly females, tend to be attracted to infants that are not their own and are often highly motivated to touch and handle them. However, species vary markedly in forms of handling and extents to which handling constitutes direct care (e.g., carrying and nursing), other affiliative behaviors, or aggression/ abuse. Here we review infant handling among primates from ultimate and proximate perspectives, focusing on a promising, but understudied hypothesized benefit—that handling enhances social bonds. We pay special attention to macaques and baboons, because infant handling in most of these species poses a special challenge in that it involves little actual care, and hence may be shaped by different and as yet unclear selective pressures from typical alloparental care. Costs, benefits, and hypothesized functions appear to vary across species based on: a) individuals’ roles (mother, handler, and infant), b) each of their characteristics, c) relationships between handlers and mothers, and d) the social context within the group. As a result, observed patterns of handling appear to be complex outcomes of the interaction of different, sometimes conflicting interests. The most promising hypotheses based on short/ medium term benefits appear to vary with breeding system, reproductive biology, socioecological factors, and life history characteristics. Explanations based on life history variables or long-term evolutionary processes related to cooperation appear to have broader applications, but nevertheless fail to explain infant handling in all its manifestations. We end by calling for more quantitative comparative and longitudinal research to further elucidate our understanding of this puzzling behavior.

The influence of phylogeny, social style, and sociodemographic factors on macaque social network structure

Among nonhuman primates, the evolutionary underpinnings of variation in social structure remain debated, with both ancestral relationships and adaptation to current conditions hypothesized to play determining roles. Here we assess whether interspecific variation in higher-order aspects of female macaque (genus: Macaca) dominance and grooming social structure show phylogenetic signals, that is, greater similarity among more closely-related species. We use a social network approach to describe higher-order characteristics of social structure, based on both direct interactions and secondary pathways that connect group members. We also ask whether network traits covary with each other, with species-typical social style grades, and/or with sociodemographic characteristics, specifically group size, sex-ratio, and current living condition (captive vs. free-living). We assembled 34-38 datasets of female-female dyadic aggression and allogrooming among captive and free-living macaques representing 10 species. We calculated dominance (transitivity, certainty), and grooming (centrality coefficient, Newman's modularity, clustering coefficient) network traits as aspects of social structure. Computations of K statistics and randomization tests on multiple phylogenies revealed moderate-strong phylogenetic signals in dominance traits, but moderate-weak signals in grooming traits. GLMMs showed that grooming traits did not covary with dominance traits and/or social style grade. Rather, modularity and clustering coefficient, but not centrality coefficient, were strongly predicted by group size and current living condition. Specifically, larger groups showed more modular networks with sparsely-connected clusters than smaller groups. Further, this effect was independent of variation in living condition, and/or sampling effort. In summary, our results reveal that female dominance networks were more phylogenetically conserved across macaque species than grooming networks, which were more labile to sociodemographic factors. Such findings narrow down the processes that influence interspecific variation in two core aspects of macaque social structure. Future directions should include using phylogeographic approaches, and addressing challenges in examining the effects of socioecological factors on primate social structure.

Primate Kinship: Contributions from Cayo Santiago

Research on Cayo Santiago and Japan deserves credit for launching the study of primate kinship and for continuing to help shape it in important ways. This review describes the origins of kinship research on Cayo Santiago, beginning with Donald Sade's pioneering work establishing the concepts of kin preferences, matrilineal dominance systems and incest avoidance. It then reviews subsequent research by later Cayo Santiago researchers and alumni, focusing primarily on maternal kinship. Together these researchers have greatly expanded our knowledge of kin preferences in rhesus in terms of (i) what age-sex classes, behaviors and types of kin show them, (ii) the ways in which kinship interfaces with rank, sex, age, and dispersal patterns, and (iii) the graded and variably limited nature of kin preferences in terms of degree of relatedness. Second, the argument for kin selection at least for some types of behavior has survived challenges posed by several alternative explanations, and has been both strengthened by recent findings of paternal kin preferences and narrowed by studies showing that unilateral altruism may extend only to very close kin. Third, work on Cayo Santiago has contributed to an appreciation that both current conditions and inherent social characteristics may influence the strength of kin preferences, and fourth, it has contributed to an understanding of the possible origins of our own species' family systems. Cayo Santiago became a leader in kinship research in large part because of management practices that produce known extended lineages. These lineages have promoted and accelerated research on kinship, prompting other researchers to investigate its importance in other groups and species, where its effects only then became clear. The extended lineages remain valuable tools for research on a species that lives in a broad range of environments in the wild, including those with key parallels to Cayo Santiago.

Functions of multiple play signals in free-ranging juvenile rhesus macaques (Macaca mulatta)

Some mammals, including some nonhuman primates, use multiple play signals during social play that convey the playful mood or intention of the signaler. However, why single species use multiple play signals has not been investigated. We recently identified seven such signals among free-ranging juvenile rhesus monkeys (Macaca mulatta) on Cayo Santiago, Puerto Rico, all of which predict the imminent occurrence of play. Here we ask whether the use of these multiple signals may have more precise or multiple functions. Specifically, we ask whether different play signals are associated with different (1) types of play to come, (2) intensities of play, (3) initiators of play and/or (4) distances at which the signal is given. Our results indicate that most signals were disproportionately associated with one or more aspects of play. For example, gamboling was associated with play that is initiated at a distance, crouch-and-stares were associated with chasing play and intense play, and leg-peeks were associated with play initiated by the receiver, as opposed to the signaler. These nonrandom associations suggest that play signals, most of which are conspicuous body signals, are not merely redundant variants of a single general function to transmit a playful mood. Rather they may be used more selectively in a variety of play contexts in which it may be beneficial to reinforce, clarify or emphasize the playful intention of the signaler. At the same time, most are not associated with particular contexts in a highly exclusive or simple manner. As such further research is needed to determine whether they are examples of functionally referential signaling.

Consistency of dominance rank order: a comparison of David's Scores with I&SI and Bayesian methods in macaques

In nonhuman primate social groups, dominance ranks are usually assigned to individuals based on outcomes of dyadic agonistic encounters. Multiple approaches have been used, but currently there is no consensus. One approach, David's Scores (DS), offers dual advantages of yielding cardinal scores that may in turn be used to compute hierarchical steepness. Here we correlate rank orders yielded by DS with those yielded by both the traditionally used I&SI approach and the recently proposed parametric Bayesian approach. We use six datasets for female macaques (three despotic and three tolerant groups), and 90 artificially generated datasets modeling macaque groups. We also use the artificial datasets to determine the impact of three characteristics (group size, interaction frequency, and directional asymmetry of aggression) on the magnitude of correlation coefficients, and assess the relative utility of two indices used to compute DS: Dij versus Pij. DS-based rank orders were strongly positively correlated with those yielded by the other two approaches for five out of the six macaque datasets, and for the majority of artificial datasets. Magnitudes of correlation coefficients were unrelated to group size or interaction frequency, but increased with directional asymmetry, suggesting methodological inconsistencies were more likely when dyads had more frequent reversals in directions of aggression. Finally, rank orders calculated using the Dij and Pij indices were similarly consistent with orders from other methods. We conclude that DS offers consistent estimates of rank orders, except perhaps in groups with very low levels of aggression asymmetry. In such "tolerant" groups, we suggest that the relatively greater methodological variability in rank orders may reflect behavioral characteristics of tolerant groups rather than computational inconsistencies between methods. We hypothesize that this quality may be quantified using posterior probability scores of Bayesian rank orders and may also index macaque social styles.

Hierarchical steepness, counter-aggression, and macaque social style scale

Nonhuman primates show remarkable variation in several aspects of social structure. One way to characterize this variation in the genus Macaca is through the concept of social style, which is based on the observation that several social traits appear to covary with one another in a linear or at least continuous manner. In practice, macaques are more simply characterized as fitting a four-grade scale in which species range from extremely despotic (grade 1) to extremely tolerant (grade 4). Here, we examine the fit of three core measures of social style-two measures of dominance gradients (hierarchical steepness) and another closely related measure (counter-aggression)-to this scale, controlling for phylogenetic relationships. Although raw scores for both steepness and counter-aggression correlated with social scale in predicted directions, the distributions appeared to vary by measure. Counter-aggression appeared to vary dichotomously with scale, with grade 4 species being distinct from all other grades. Steepness measures appeared more continuous. Species in grades 1 and 4 were distinct from one another on all measures, but those in the intermediate grades varied inconsistently. This confirms previous indications that covariation is more readily observable when comparing species at the extreme ends of the scale than those in intermediate positions. When behavioral measures were mapped onto phylogenetic trees, independent contrasts showed no significant consistent directional changes at nodes below which there were evolutionary changes in scale. Further, contrasts were no greater at these nodes than at neutral nodes. This suggests that correlations with the scale can be attributed largely to species' phylogenetic relationships. This could be due in turn to a structural linkage of social traits based on adaptation to similar ecological conditions in the distant past, or simply to unlinked phylogenetic closeness.

Changes in yearling rhesus monkeys' relationships with their mothers after sibling birth

The birth of a new sibling is believed to signify an abrupt and important transition in a young primate's relationship with its mother-one that is of potential importance from at least three theoretical perspectives: attachment theory, parent-offspring conflict theory, and dynamic assessment models. This study examines changes in relationships between free-ranging yearling rhesus monkeys (Macaca mulatta) and their mothers concomitant with the birth of the mother's next infant, and tests predictions derived from each theoretical perspective. We observed 31 yearling rhesus on Cayo Santiago, Puerto Rico, 3 months before and 3 months after their siblings' births, using focal animal sampling methods. Changes in measures related to mother-yearling interaction and yearling distress were examined using repeated-measures analysis of variance. After sibling birth, mothers and yearlings abruptly reduced amounts of time in contact and increased amounts of time at a distance and out of sight of one another. Mothers and yearlings played approximately equal roles in bringing about decreases in proximity, and yearlings took the primary roles in bringing about decreases in contact. Rates of maternal aggression toward yearlings increased immediately and markedly after birth, possibly providing yearlings with early cues regarding subsequent decreased levels of maternal care. There were no marked increases in overt signs of yearling distress (e.g., vocalizations or tantrums) following the births. We conclude that yearlings generally acquiesced to reduced levels of care, responding behaviorally with increased independence and maturity. In this sense, our study provides preliminary support for dynamic assessment models over attachment theory and parent-offspring conflict theory models.

Development of kin bias among rhesus monkeys: maternal transmission or individual learning?

We examined the possible roles of maternal transmission and independent learning in the development and perpetuation of kin networks across generations of free-ranging rhesus monkeys, Macaca mulatta, on Cayo Santiago, Puerto Rico. We tested predictions derived from maternal transmission and independent learning hypotheses by examining the extent to which variation in the degree of kin bias displayed by individual infants was related to variation in mother-infant interaction and aspects of the infant's social environment. High levels of kin bias in infants were related independently to high levels of both proximity to the mother and to potential social risk. At 25-30 weeks of age, infants displayed degrees of kin bias that were moderately correlated with those of their mothers. However, infants that spent large amounts of time near the mother did not necessarily develop degrees of kin bias that were highly similar to those of their mothers. The extent to which infants developed degrees of kin bias similar to their mothers was significantly correlated with the degree to which they experienced similar levels of social risk. The results suggest that, while intense mother-infant interaction contributes to the development of high degrees of kin bias in infants, the perpetuation of similar degrees of kin bias across generations may depend on mothers and infants having similar experiences with mutual kin and nonkin. We suggest that the perpetuation of kin bias across generations may be viewed as socially biased independent learning (Galef 1995, Animal Behaviour, 49, 1325-1334). Copyright 1999 The Association for the Study of Animal Behaviour.

A preliminary description of responses of free-ranging rhesus monkeys to brief capture experiences: behavior, endocrine, immune, and health relationships

A cohort of free-ranging rhesus monkeys has been followed since birth in 1994 on the island of Cayo Santiago, Puerto Rico. At 3 years of age, subjects were trapped and blood samples were collected after capture and prior to release the following day. Blood samples were processed for natural cytotoxicity toward xenogeneic tumors, phenotyping, and plasma hormones. Intestinal parasites were determined from fresh stool samples collected during trapping. Data were also available from the previous year for antibody titers to latent viruses prevalent in this population. Behavioral traits of each monkey were characterized using a previously developed trait scale for rhesus monkeys. Natural cytotoxicity toward both K562 and Raji targets declined from capture until release the following day. Plasma cortisol rose and plasma prolactin and growth hormone fell during the period of captivity; a rise in insulin was significant. It was expected that individual differences in behavioral traits might predict immune and hormone levels at the time of capture or changes in these parameters during the capture period. Although behavioral adjectives tended to cluster along three orthogonal dimensions (Insecurity, Irritability, and Sociability), they bore no relationship to the physiological parameters collected acutely (in vitro immune and endocrine parameters). The individual difference markers of gender and maternal rank were not related to the magnitude of the observed changes in these in vitro parameters, either. However, an in vivo measure (CMV titer) was related to individual differences in Irritability. It was concluded that the magnitude of the stress associated with capture overwhelmed the individual difference effects.

On the quantification of suckling intensity in primates

The inhibitory effect that suckling has on the reproductive function of primate mothers varies as a function of the intensity with which they are suckled. Here we present an easily computed index of one parameter of suckling intensity, namely the temporal patterning of suckling bouts. High intensity suckling is characterized by frequent nursing bouts demarcated by short interbout intervals. Therefore, our suckling index is based on the brevity of observed interbout intervals, more specifically the proportion of such intervals that fail to exceed a criterion length. The index is an appropriate means of making interspecific comparisons of the development of infant suckling and is well suited for application to field data that include interbout intervals that were not observed in their entirety. To demonstrate its utility, we apply the index to field data collected on the suckling behavior of free-ranging rhesus monkey (Macaca mulatta) infants in India. In this context, we demonstrate that, in rhesus, between-infant differences in suckling intensity manifest themselves early in the postpartum period and contribute to between-female differences in the timing of first mating postpartum.

Models of Affiliative Relationships Among Free-Ranging Rhesus Monkeys (Macaca Mulatta)

Abstract

Understanding the relative importance of various hypothesized organizing principles of affiliative relationships among female macaques has been problematic at least partly because researchers have lacked adequate statistical techniques for teasing apart the roles of maternal kinship and rank distance, and because criteria for kinship have varied across studies. We examined the extent to which maternal kinship and rank distance are independently associated with levels of affiliative interaction among free-ranging adult females rhesus monkeys (Macaca mulatta) on Cayo Santiago, Puerto Rico. We used a multiple regression extension of the Mantel test to evaluate three models, each using different criteria for kinship. In all three models, kinship emerged as a strong correlate of affiliative interaction. However, the degree to which rank distance correlated with affiliative interaction varied across models. Hence, the choice of criteria for kinship affected the apparent importance of rank distance in multi-generational groups. A model using graded rather than discrete criteria of kinship (i.e. degrees of relatedness instead of kin vs non-kin) but differentiating only close kin relationships (r 0.125) rather than all kin relationships (r 0.0005) accounted for the largest proportion of the total variance. These results support suggestions that adult female relationships are organized around several levels of kinship through maternal lines, and not simply by crude distinctions of kin vs non-kin. However, when kin are separated from common ancestors by more than a few links, females appear to behave towards related individuals much as they do toward non-kin.

Models of Affiliative Relationships Among Free-Ranging Rhesus Monkeys (Macaca Mulatta)

Abstract

Several organizing principles based on maternal kinship and/or dominance relationships, have been proposed to explain the structure of female-female macaque affiliative relationships. Social interactions among adult rhesus females of one free-ranging social group on Cayo Santiago, Puerto Rico were observed for four consecutive years to determine the extent to which patterns of affiliative interaction met several predictions of three such hypothesized organizing principles: kin-based attractiveness, attraction-to-high-rank and the similarity principle. We employed a multiple regression extension of the Mantel test (Smouse et al., 1986) to test the independent effects of kinship and rank distance on measures of affiliation and reciprocity. Close kin not only engaged in more affiliative behaviour than distant kin (see our companion paper, Kapsalis & Berman, this volume), they were more likely to support one another in agonistic encounters and to exchange grooming for alliance support and access to drinking water. We found evidence that low-ranking females were attracted to high-ranking females in some years of study, and that grooming by low-ranking females was exchanged with tolerance at a monopolizable resource by high-ranking grooming partners. However, we were unable to test conclusively for the effects of competitive exclusion. Little evidence was found to support the predictions of the similarity principle. We concluded that kin-based attractiveness was probably the primary organizing principle operating in the study group but that elements of attraction-to-high-rank may operate in concert to some extent.

Responses of free-ranging rhesus monkeys to a natural form of social separation. I. Parallels with mother-infant separation in captivity

Observations of 23 free-ranging rhesus monkey infants on Cayo Santiago, Puerto Rico, indicated that mothers' first postpartum estrous periods were marked by large increases in the amount of time infants were separated from their mothers, by disturbances in mother-infant relationships, and by increases in infant distress behavior. When their mothers resumed mating, most infants showed signs of agitation; a few briefly showed indications of depression. Male infants responded to their mothers' resumption of mating by playing more, whereas females engaged in less play and more allogrooming. The results suggest (a) that basic parallels exist between the behavioral responses of rhesus infants to their mothers' resumption of mating in the field and to forcible separation from their mothers in captivity and (b) that early separation experiences may play a role in the normal development or manifestation of sex differences in behavior.

Specific antibody levels in free-ranging rhesus monkeys: relationships to plasma hormones, cardiac parameters, and early behavior

Levels of tetanus-specific antibodies were assessed in free-ranging, yearling rhesus monkeys following prophylactic immunization with tetanus toxoid. Each subject's behavior had been observed between 11 and 25 weeks of age and approximately 2 months later during its mother's first concentrated mating period as a part of another study. Prior to immunization, at approximately 1 year of age, cardiovascular parameters, and several plasma parameters [cortisol, adrenocorticotrophic hormone (ACTH), growth hormone (GH), interleukin-2 (IL-2), and total plasma immunoglobulin G (IgG)] were measured during a brief period of captivity. Antibody titers noted approximately 2 weeks after immunization were related to cardiovascular parameters. Thus, yearlings with high heart rates and low heart rate variability during captivity had the highest tetanus-specific serum IgG. Levels of plasma cortisol, ACTH, total IgG, and IL-2 noted at the time of capture were unrelated to subsequent antibody levels. Antibody titers were, however, positively correlated with GH noted immediately following capture on the day prior to immunization. Antibody titers were also related to the infants' behavior observed during their mother's first concentrated mating period. Infants who were most distressed (high levels of distress vocalization) when their mother resumed mating (a time particularly stressful for free-ranging rhesus infants) showed lower antibody titers to tetanus immunization as a yearling. The present observations add support to the existence of a relationship between behavior during exposure to an early stressor and later immune regulation and that certain cardiovascular parameters may be related to certain indicators of immunoregulation.

Trapping activities and mother-infant relationships on Cayo Santiago: a cautionary tale

Trapping activities in the Cayo Santiago rhesus monkey colony are normally limited to January and February of each year. The year 1984 was exceptional in that the trapping period was extended until early May. This paper examines the effects of the extended trapping period on mothers and infants who observed trapping activities but were not directly involved in them. Mother-infant pairs exposed to extended trapping activities spent significantly more time in contact and less time at a distance from each other than those not exposed, both during the time of exposure and for several weeks afterward. There were also consistent nonsignificant tendencies for exposed mothers to reject their infants less, to initiate a higher proportion of their contact and to play a larger role in maintaining proximity. This pattern of differences is consistent with the suggestion that mothers reacted to the extended trapping period by protecting their infants more and by encouraging independence less. The results demonstrate the sensitivity of mothers to human disturbance and illustrate the value of management policies like those on Cayo Santiago, that minimize human disturbance and restrict trapping to a consistent and limited period each year.