Irwin S. Bernstein

Juvenile primates. Life history, development, and behavior

The editors indicate that this book is intended to stimulate research on juveniles as a counterbalance to the usual focus on adult and infant behavior. Pereira, in his concluding chapter, states that whereas earlier studies focused on socialization effects, the present biological perspective asks what juveniles need to survive and to reproduce. He indicates that theories from both perspectives have yet to be tested. The first set of chapters identifies growth, survival, feeding capabilities, reproductive competence, and the skills and time necessary to maximize lifetime reproductive success as the interrelated variables in theories based on evolutionary biology. Individuals must survive the juvenile period and maximize reproduction during adult years, but environmental constraints produce a multifactorial model that defies any simply mathematical solution. The juvenile period, like play, seems to entail high costs and one usually searches for compensating benefits. Whereas play and other activities of a juvenile may contribute to abilities in adult life, several authors conclude that juvenile activities function primarily for survival in the juvenile period. In essence, the juvenile stage may be a consequence of environmental constraints regulating growth and reproduction rather than functioning as a period to acquire skills for adult life. There are no absolute criteria demarcating the juvenile period. The weaning process may be prolonged and some authors prefer to define the end of infancy not by weaning but instead by the capacity to survive without parental care. Likewise, puberty is a process that may span several years and reproductive competence entails both physiological capacity and social skills. This transitional period to full adult status invites differences of opinion and even inconsistency such that, for some, only males go through

Plasma Testosterone Levels in the Male Rhesus: Influences of Sexual and Social Stimuli

Four adult male rhesus monkeys were provided access individually to a group of receptive females. Each male assumed dominance and engaged in frequent copulations. Plasma testosterone levels increased two- to threefold during this period. Next, each male was subjected to sudden and decisive defeat by a large all-male group, and plasma testosterone fell following this experience. Two males were later reintroduced to the females, and plasma testosterone rose rapidly to the previous elevated levels.

Dominance, aggression and reproduction in primate societies☆

Abstract Dominance relationships in primate societies are generally inferred by analyses of agonistic interactions. This aspect of social organization is so striking in macaque and baboon societies that many theoreticians have postulated selective mechanisms operating on the genetic attributes which contribute to high dominance rank. Alpha males were hypothesized to increase their genetic fitness by successfully competing with other males for access to ovulating females. Evidence relevant to these speculations has been mixed. Whereas some investigators found alpha males had near exclusive sexual access to females, others failed to confirm preferential access to ovulating females. Indeed, considerable variability in competition for females existed not only among species, but also among troops of the same species living in different habitats. Further, partner selection was not an exclusive male prerogative; females proved to express active preferences for particular males as sexual partners, and these preferences were not related to high male aggressivity. Alpha males, however, were noted to maintain their positions through social skills as members of a central core or alliance, and high rank was related primarily to seniority. Moreover, alpha males responded actively to challenges to the troop and were judged to contribute significantly to the survival of infants. It was therefore hypothesized that increased genetic fitness related to the increased survival of immature animals in the troop, most of which would already be the offspring of senior (and hence alpha) males. Selection would then be for the social skills leading to successful alliances in troop defense. Such skills might also relate to female partner preferences thus increasing the reproductive effectiveness of alpha males at any point in their careers, including years prior to and following their assumption of alpha rank.

Seasonal rhythm in plasma testosterone levels in the rhesus monkey (Macaca mulatta): A three year study

Abstract Behavioral and endocrine data were collected over a 3 yr period from a rhesus monkey breeding colony maintained in an outdoor enclosure. Routine data collection included recording all observed reproductive behavior and the date of all births. Blood samples were obtained at least once monthly from the sexually mature males in the group, and testosterone content determined via radioimmunoassay. The breeding group exhibited a seasonal pattern of mating and births such as is typical of the species. Copulatory activity was restricted to a 5 month period commencing in the early fall of each year, with all births recorded in a corresponding span between March and August. Plasma testosterone concentration showed a distinct seasonal rhythm, peaking each year in October or November at a mean of about 1200 ng/100 ml. During periods of sexual inactivity, plasma testosterone values fell to a low of about 200 ng/100 ml. The results demonstrate a correlation between seasonal breeding activity and increased levels of circulating testosterone in the rhesus monkey, and are supportive of the postulate that other seasonally observed behavior patterns (e.g., increased aggression) also may be mediated by higher testosterone levels.

SOCIAL ROLES IN A RHESUS MONKEY GROUP

A society is comprised of a variety of interdependent roles (PARSONS & SHILS, 1951), and specific cues indicate the actual and potential roles of individuals (COTTRELL, I942; SARBIN, I954). The complexity of interaction patterns associated with a role and the number of distinct roles in a group may be considered to be related to the complexity of a social organization. Societies may therefore be compared by detailed analysis of the role patterns contained. The determinants of a role in human societies include biological and psychological factors operating in combination to produce consistent response patterns. These same factors operate in nonhuman primate groups, and field studies suggest that a degree of role differentiation may be found in all primate groups. The present paper presents an analysis of differentiated response patterns in a rhesus monkey group. The group was selected to approximate the composition of a natural group (SOUTHWICK, BEG & SIDDIQI, i96ia, b), and the extensive literature available for the rhesus monkey suggested several factors which might operate as determinants of roles. S. BERNSTEIN & MASON (I962), CARPENTER (I942b), MASON (I963), and ROSENBLUM (I96I) have indicated some ways in which age influences the behavior of rhesus monkeys. CARPENTER (I942a) and MASON, GREEN & POSEPANKO (I960) have demonstrated sex to be another powerful determinant. CHANCE (1956) has discussed some behavioral attributes of dominant rhesus monkeys, MASLOW (I940) has theorized at some length on the significance of status, CARPENTER (I954) has operationally defined status in terms of priority to

The Interaction of Hormones, Behavior, and Social Context in Nonhuman Primates

Hormones are often regarded as one independent variable responsible for the behavior (the dependent variable) of an individual. Hormones are seen as the physiological mechanism underlying behavior and are treated as a “cause” of certain behavioral patterns—“behavioral patterns,” because hormonal levels are not viewed as stimuli that release specific fixed action patterns but as the regulators of motivational states that increase or decrease the probabilities of specific classes of response to environmental stimuli.

Stability of the status hierarchy in a pigtail monkey group (Macaca nemestrina).

Multiple measures of dominance were compared using a total of forty-eight pigtail monkeys (Macaca nemestrina). A measure of ‘peck-order’ was selected and changes in the status hierarchy were studied during a 5-year period. The hierarchy was found to be remarkably stable and even the natural replacement of the alpha male produced only moderate changes in the rank order structure.

Tumor Immunity Produced by the Intradermal Inoculation of Living Tumor Cells and Living Mycobacterium bovis (Strain BCG)

The intradermal inoculation of mixtures containing living tumor cells and living Mycobacterium bovis (strain BCG) into unimmunized syngeneic guinea pigs results in an inflammatory reaction to the BCG, and there is no progressive tumor growth. In the absence of BCG the tumor grows progressively, metastasizes, and kills the animal. By conventional methods, it has not been possible to immunize syngeneic guinea pigs to the tumor used. Guinea pigs that receive mixtures of BCG and tumor cells, however, develop specific systemic tumor immunity as measured by delayed cutaneous hypersensitivity and by suppression of tumor growth.

The Lutong of Kuala Selangor

A field study of the Lutong, (Presbytis cristatus) was conducted in Malaya. Lutong troops were observed for more than 1000 hours and were found to be markedly territorial. Only one control male lives in each troop and he actively defends the territory against incursions by other lutong males. Each troop moves slowly through its territory feeding and resting and comes into frequent visual contact with adjacent troops. Each troop is a well organized social unit but only the control males show consistent hostility to one another when troops meet. Grooming, play, sexual responses, maternal behavior and agonistic episodes are described as well as travel, feeding and diurnal patterns. These patterns appear similar to those reported in other Presbytis species, but contrast markedly with macaque and baboon reports. Differences in behavior between species of Presbytis do not exceed differences reported in the same species by different observers in different areas.

The social component of dominance relationships in rhesus monkeys (Macaca mulatta)

An all-male rhesus group was added to a second group, one animal at a time, at weekly intervals, in reverse order of their dominance ranks. Significant positive correlations prevailed for the host group dominance ranks throughout the study, but the dominance ranks of the introduced males were random with respect to their original ranks. A second experiment repeatedly introduced the alpha and beta males of a multi-male heterosexual group into a second group where they were the lowest-ranking animals. On each return they reclaimed alpha and beta positions. When the alpha and beta males of the second group were introduced to the first group, they became the lowest-ranking animals in the group. Reversal of the direction of introduction again demonstrated that relative ranks were dependent on the social context.