Biomedical subjects

W A Mason

Publications and source records attributed to W A Mason.

At least 37 records · Page 2Linked to original sources

PubMed1997

Autonomic balance in Saimiri sciureus and Callicebus moloch: relation to life-style.

Previous research has shown heart rate to be substantially higher in squirrel monkeys (Saimiri sciureus) than titi monkeys (Callicebus moloch). In order to evaluate whether species differences in heart rate can be accounted for by contrasting patterns of autonomic activity, heart rate in response to novel test conditions was compared using standard pharmacological agents that selectively block the sympathetic (propranolol) or parasympathetic (atropine) components of the autonomic nervous system. Squirrel monkeys were found to exhibit greater sympathetic response to novelty than titi monkeys. In contrast, sympathetic activity in titi monkeys, but not squirrel monkeys, was quickly counteracted by a strong parasympathetic response. Intrinsic heart rates, estimated by blocking both parasympathetic and sympathetic input to the heart, were within the ranges of values predicted by body weight. Heart rate for titi monkeys stabilizes at intrinsic heart rate, whereas heart rate for squirrel monkeys is maintained well above intrinsic heart rate in a novel environment. The contrast between species in autonomic balance is consistent with and probably contributes to each species characteristic mode of interacting with their social and non-social environment.

Analysis of Variance↗

PubMed1996

Seasonality in squirrel monkeys (Saimiri sciureus): social facilitation by females.

The extent to which social living arrangements influenced seasonal changes in physiology and behavior was examined in adult squirrel monkeys (Saimiri sciureus). Data were collected over 20 months (encompassing two breeding seasons) from animals that were housed in three mixed-sex social configurations that varied in the number of heterosexual and isosexual social partners. For both sexes, the presence of multiple females was found to facilitate reproduction. Females housed with other females were more likely to exhibit seasonal ovarian cyclicity and tended to have higher conception rates. Social facilitation of reproduction was particularly prominent for subordinate females. The presence of same-sex companions also resulted in reduced adrenocortical output in females during the first nonbreeding season. In males, the availability of multiple females increased plasma testosterone levels, except in the presence of more dominant males. Seasonal increases in male weight coincided with increased cortisol levels and were most prominent in social groups containing multiple females. The influence of multiple females on male seasonality occurred despite the finding that male-female interactions were infrequent and, in fact, occurred less frequently when isosexual partners were available. Unexpectedly, affiliative social interactions between same-sex and opposite-sex partners occurred less frequently during the breeding season. As expected, behaviors associated with sex tended to increase during the breeding season. Very little agonism was observed during the course of the study and there was no evidence of interanimal competition for mates.

Animals↗

PubMed1996

Effect of infants on adult social relations in the squirrel monkey (Saimiri Sciureus).

7 groups of squirrel monkeys were observed to assess the effect of infants on social interactions and interanimal distances among adult members of their natal groups. Each group contained one or two infants, 5 to 7 months of age at the start of the study. Infants initiated affiliative and playful interactions with all adults, whereas adults directed few mostly antagonistic, interactions toward infants. Following the removal of infants from groups, distances between adults decreased and adult affiliative interactions increased more than 100%. The results indicate that infants within the age range examined can have a pervasive, primarily inhibitory, influence on adult social relationships.

Aging↗

PubMed1995

Responses of infant titi monkeys, Callicebus moloch, to removal of one or both parents: evidence for paternal attachment.

The response to parental separation in infant titi monkeys was evaluated. Separation from the mother for 1 hr did not elicit an adrenocortical response from the infant unless the father was also removed. Separation from the father elicited a significant elevation in adrenocortical activity even when the mother remained with the infant during the separation period. Infants showed the highest cortisol levels and vocalization rates when both parents were removed and the infant remained alone in the living cage for 1 hr. As in previous research, infants maintained higher levels of contact with the father than with the mother. The results indicate that in this monogamous New World primate, the father is the primary attachment figure for the developing infant.

Animals↗

PubMed1995

Endocrine sensitivity to novelty in squirrel monkeys and titi monkeys: species differences in characteristic modes of responding to the environment.

The present study examined plasma cortisol and behavioral responses to environmental novelty in squirrel monkey and titi monkey male-female pairs. Overall, seemingly trivial increments in novelty evoked sustained plasma cortisol elevations. In individually tested animals, the minimal level of novelty sufficient to evoke a cortisol response was smaller, and the ability of the response to discriminate among levels of novelty was greater, in titis than in squirrel monkeys. When tested with the pairmate, the sensitivity of the response was reduced in titis but not in squirrel monkeys. Behavioral measures were not as sensitive to novelty as was the cortisol response. The results suggest that differential endocrine responsiveness to novelty is an important physiological concomitant to previously described differences between squirrel monkeys and titi monkeys in their characteristic modes of relating to the environment.

Animals↗

PubMed1992

Sexual segregation in squirrel monkeys (Saimiri sciureus): a transactional analysis of adult social dynamics.

Female agonism against males and male interventions in social transactions between the sexes are 2 explanations for the low rates of social engagement observed between male and female squirrel monkeys (Saimiri sciureus). These possibilities were evaluated by comparing the frequency, structure, and content of transactions between the sexes in 3 experimental social units: male-female pairs, single-male-multifemale groups, and multimale-multifemale groups. Affiliative transactions between the sexes occurred 3-5 times less often in multimale-multifemale groups than in male-female pairs and in single-male-multifemale groups. Intermale agonism in the multimale-multifemale groups often coincided with ongoing transactions between the sexes, whereas female agonism against males was rather uncommon in all social units. The results failed to support the female agonism hypothesis and indicate a need for more detailed studies of intermale social dynamics.

Agonistic Behavior↗

PubMed1991

Sociophysiology of relationships in squirrel monkeys. I. Formation of female dyads.

Physiological and behavioral consequences of formation of female-female relationships were investigated in adult squirrel monkeys. Plasma cortisol, heart rate, and behavior were evaluated during confinement in a test cage while animals were housed alone, during the first hour of isosexual pair formation, and while animals were housed as isosexual dyads. In addition, basal cortisol levels were assessed both before and after pair formation, as were behavioral and cardiovascular responses to social and nonsocial stimulus presentations. Basal cortisol levels underwent a marked and sustained reduction following formation of pairs, independent of both dominance status and the quality of social interactions between pairmates. In contrast, adrenocortical responsiveness was not altered by social conditions, apart from a modest and transitory difference between dominant and subordinate females in their initial response to pair formation. Heart rate declined sharply during each test session, but did not reliably differentiate social conditions, stimulus conditions, or dominance status. These findings contrast with results of a parallel study of male squirrel monkeys and suggest that isosexual relationships in males and females are associated with different sociophysiological processes.

Animals↗

PubMed1991

Breeding readiness in squirrel monkeys: female-primed females are triggered by males.

The South American squirrel monkey (Saimiri) shows pronounced annual variations in reproductive activity. We investigated the contribution of social stimulation to breeding readiness, as reflected in behavior and gonadal hormones. A previous study indicated that formation of new heterosexual pairs can induce breeding readiness in males, but not in females. In the present study we examined the response of individually housed females to the formation of triads of unacquainted females and, subsequently, the response of these triads to the introduction of a single male. The formation of the all-female group was accompanied by a marked reduction in basal cortisol levels. Introduction of a male to such a group promptly induced breeding readiness in the females, as indicated by increased gonadal hormone production and cyclic variation in estrogen and progesterone levels. The contrasting responses of group-living or single females to a new male suggest that at least two processes are involved in the induction of breeding readiness by group formation in females. One is a "priming" effect resulting from interfemale stimulation: the other is a "triggering" effect resulting from the presence of a male.

Animals↗

PubMed1991

Effects of social interaction on well-being: development aspects.

The scientific need for nonhuman primates that are born and raised in captivity seems certain to increase and with it, the concern for managing the social development of individual animals so as to maximize their utility throughout a potentially long career. This practical objective is not only compatible with a concern for psychological well-being, but presupposes similar aims and criteria. For both concerns the most reliable guidelines are derived from basic research. The data available indicate that primate social development is directional, proceeding from extreme dependence on care-givers initially (subserved by mother-directed behaviors) toward relative autonomy and adult competence (dominated by other-directed behaviors). Individuals are not passive recipients at any point in this process, rather they are active participants in their development, engaged with their surroundings and responding selectively to what the environment affords. From this standpoint, developmental effects are the outcome of transactions with the environment. They are emergent phenomena, neither wholly independent of environmental influences, nor completely determined by them. It follows that the long-range utility and well-being of captive animals will be served well if they are able to select those with whom they will interact and modes of interaction that are appropriate to their level of development and current motivational state. This can generally be accomplished by permitting individuals to develop, at least through weaning, in the company of their biologic mothers within an approximation of a species-normal social group. When such latitude is impossible, the social environment should be arranged with the individuals' developmental levels as a primary concern.

Animals↗

PubMed1989

Behavioral and endocrine consequences of heterosexual pair formation in squirrel monkeys.

The South American squirrel monkey (Saimiri sciureus) typically lives in large social groups containing several individuals of all age/sex categories. When living in established heterosexual pairs, reproduction in this seasonally breeding primate is poor. We attempted to induce breeding activity in pair-housed monkeys by forming new heterosexual pairs just prior to the breeding season. Breeding readiness, as reflected in behavior and gonadal hormones, was induced in males, but not in females. Males also showed persistent increases in cortisol levels following formation of new heterosexual pairs; females did not. The results indicate that social stimulation provided by a single novel female is sufficient to enhance breeding readiness in male squirrel monkeys. Females, on the other hand, are apparently unresponsive to a single male whether novel or familiar; this may account for the poor reproductive success in squirrel monkeys housed in heterosexual pairs.

Animals↗

PubMed1988

Formation and expression of filial attachment in rhesus monkeys raised with living and inanimate mother substitutes.

The formation and expression of filial attachment was investigated in rhesus monkeys raised with dogs or inanimate mother substitutes in a longitudinal study spanning the first 4 years of life. At 2 months monkeys were identified within each rearing group as strongly attached or weakly attached, as measured by proximity, contact and clinging to the mother substitute in the living cage and in a novel room, and by differences in levels of distress vocalization and heart rate when they were alone and in the presence of the substitute mother in a novel room. By 4 months, all monkeys were attached, and the strongly attached and weakly attached monkeys of the first age-period were no longer distinguishable on any measure. The attachment was specific to the substitute mother. It was not exclusive, however, inasmuch as similar responses were elicited by a stranger of the same type as the substitute mother, although the stranger was less effective. The attachment figure was also influential when it could be seen but not touched. Evidence of attachment to the substitute mothers persisted until the end of testing at 44 months. Comparison of rearing groups support the hypothesis that the principal effect of living and inanimate mother substitutes is on responsiveness, rather than on the attachment process per se.

Animals↗

PubMed1988

Interspecific contrasts in responses of macaques to transport cage training.

Corticosteroid values in response to brief confinement in a transport cage were compared between rhesus, bonnet, and crabeating macaques before and after they were trained to enter the cage. Behavioral data were collected to assess performance during training. Species differences were found both in training measures and in corticosteroid response to confinement in the transport cage after training. Bonnets took longer to train than rhesus or crabeaters. Rhesus showed the smallest adrenocortical response to cage confinement after training and crabeaters the greatest, suggesting that this group habituated more slowly to confinement than the other two groups. The results have implications for choice of experimental subject species and for management and husbandry of laboratory primates.

Adrenal Cortex Hormones↗

PubMed1986

Contrasting responses to intruders and to involuntary separation by monogamous and polygynous New World monkeys.

The strength and quality of the relationship between heterosexual pairmates were compared in two species of New World monkeys, the polygynous squirrel monkey (Saimiri) and the monogamous titi monkey (Callicebus). This was accomplished by measuring behavioral and adrenocortical responses to intruders and to involuntary separation from the pairmate. The species diverged sharply in their responses to these conditions. For titi monkeys, the presence of an intruder resulted in a marked increase in behavioral signs of agitation, which were more prominent in the subject of the same sex as the intruder. Most male titi monkeys showed an increase in plasma cortisol in the presence of a male intruder; this pattern was not seen in their response to a female intruder. Female titi monkeys showed no consistent pattern of adrenocortical response to intruders of either sex. For squirrel monkeys, the presence of an intruder resulted in increased frequency of displays in male subjects, but not in female subjects. Both sexes showed a reliable reduction in plasma cortisol, below basal levels, in the presence of a female intruder, whereas no effect on cortisol was produced by a male intruder. Titi monkeys, but not squirrel monkeys, responded to separation with a significant increase in plasma cortisol and in behavioral indices of agitation or distress.

Adrenal Cortex↗

PubMed1986

Differences between Saimiri sciureus and Callicebus moloch in physiological responsiveness: implications for behavior.

The New World primates Callicebus moloch and Saimiri sciureus differ markedly in life modes. Physiological responsiveness (heart rate, cortisol) of these related taxa was compared in two situations that differed in the presumed degree of stress imposed, exposure to a novel environment and physical restraint. In both situations, Saimiri exhibited higher initial levels of heart rate and corticosteroids. In addition, the species differed in their patterns of response to both situations. Saimiri maintained initial heart rate levels across a 1-hour exposure period, whereas Callicebus showed a marked and continuous decline in heart rate. Adrenocortical activity increased in both species in response to test situations, but the elevations in plasma corticosteroids were substantially greater for Saimiri than for Callicebus. The results indicate that the species differ with respect to organization of physiological regulatory systems in a manner consistent with behavioral contrasts between them.

Animals↗

PubMed1979

Contrasts in visual responsiveness and emotional arousal between rhesus monkeys raised with living and those raised with inanimate substitute mothers.

Rhesus monkeys were raised with dogs or inanimate surrogates in outdoor cages which provided them with complex, highly varied visual surroundings. Visual responsiveness to a variety of colored transparencies was investigated in three experiments, completed when the monkeys were between 18 and 30 mo old. Results indicated that the frequency and duration of looking at slides was significantly higher for dog-raised than for inanimate-surrogate-raised monkeys and that dog-raised monkeys were much more responsive to the novelty, complexity, ansal were obtained during the final experiment. Heart rate, vocalization, and changes in plasma cortisol were higher for monkeys raised with dogs. The frequency of most self-directed behaviors, however, was higher for monkeys raised with inanimate surrogates. Differences between rearing groups can only be the result of contrasts in attributes of the substitute mothers.

Animals↗

PubMed1978

Competitive social strategies in groups of deprived and experienced rhesus monkeys.

Behavior during competition for water was observed in 2 social groups of young rhesus monkeys (3 females, 3 males in each). Monkeys in one group were socially deprived and those in the other were socially experienced (raised with mother and agemates). Social status, based on dyadic recording of displacements at the water bottle, was predictive of a number of measures related to water consumption and social orientation in both groups, but this measure was less reliable and predictive for the experienced group than for the deprived groups, but this measure was less reliable and predictive for the experienced group than for the deprived group. A major reason for the comparatively low predictive value and reliability of status among experienced monkeys was their ability to influence the behavior of higher status members through responses directed to a 3rd party and other elaborate social strategies, many of which depended on responding to status relations between 2nd and 3rd parties. The fact that such strategies were only observed in the experienced group is a clear indication that the development of higher orders of social cognition is dependent on early social experience.

Animals↗

PubMed1978

Contrasting effects of living in heterosexual pairs and mixed groups on the structure of social attraction in squirrel monkeys (Saimiri).

The structure of social attraction was assessed in pair- and group-living squirrel monkeys (Saimiri) using paired-comparison and single-stimulus preference tests. Effects of the social environment were most prominent in females. Females housed with a single male showed sharply increased attraction to like-sex strangers and less pronounced increase in attraction to opposite-sex strangers, as compared to group-living females. Differences between pair- and group-living males were in the same direction found with females, but less extreme. Most group-living monkeys strongly preferred familiar animals to strangers regardless of sex, and like-sex to opposite-sex familiars. Change in the structure of social attractions in response to variations in the composition of the social environment appears to be an important factor in the maintenance of the species-typical grouping pattern in the squirrel monkey.

Animals↗

PubMed1977

Effects of maternal mobility, partner, and endocrine state on social responsiveness of adolescent rhesus monkeys.

The social behavior of rhesus monkeys raised for the 1st year of life with mobile (MS) or stationary (SS) cloth surrogate mothers was investigated when the animals reached 4-5 yr of age. The MS males generally refrained from social interaction during initial pairings with females, whereas SS males interacted frequently, but were more often the targets of attacks and chases from adult females than were MS males. The MS males were more likely to vary their social behavior according to the behavior of the social partner and seemed to benefit more from extended social exposure than their SS counterparts. The MS females were more similar to wild-born females than were SS females in nearly every behavior category and dimension tested. These results suggest that rearing with mobile artificial mothers improves the chances of later adaptive social adjustments in socially restricted monkeys.

Age Factors↗