Seasonal variability in spatial defence by free-ranging rhesus monkeys (Macaca mulatta)

Data on the rhesus monkeys (Macaca mulatta) of Cayo Santiago demonstrate both intergroup and seasonal variability in spatial defence. Of the five groups only one defends an area, and only during the birth season. The four non-defensive groups share two feeding stations and live in such close proximity that spatial defence would require high outputs of energy. In contrast, the group that maintains an exclusive area has its own feeding station and lives in semi-isolation on an easily defensible end of the island. Its defence of this end of the island during the birth season provides a protected area for infants and assures the group exclusive access to flowering and fruiting plants. Relaxation of this defensive behaviour during the mating season maximizes opportunities for intergroup matings.     

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.     

Social dominance and female reproductive behaviour in rhesus monkeys (Macaca mulatta)

The relationship between dominance rank and female sexual behaviour was examined in rheusus monkeys (Macaca mulatta) living in a social group. High-ranking females engaged in copulatory series as frequently as lower-ranking females. Furthermore, lower-ranking females copulated with as many available males as did high-ranking females. Social rank did appear to influence the pattern of sexual activity exhibited, in that copulatory series were more often initiated by the higher-ranking animal of the mating pair. Copulatory series involving high-ranking females were characterized by more mounts by males and were longer in duration. Higher-ranking animals interfered more often with copulatory series involving other animals, but such interference was not effective in preventing completion of the series. These data indicate that any reproductive advantage conferred to high-ranking females is not the result of sexual competition in social-living rhesus monkeys.     

The behavioral thresholds of testosterone in castrated male rhesus monkeys (Macaca mulatta)

To determine the lowest doses of testosterone propionate (TP) that cause clearcut behavioral changes in castrated male rhesus monkeys (behavioral thresholds), observations were made on eight males during successive 4-week treatment periods while they received daily doses of TP ranging from 25 μg to 12.8 mg subcutaneously. Males were tested with each of the same four ovariectomized females (32 pairs, 1408 one-hour behavior tests). Two females were untreated and the other two received either 5 or 15 μg estradiol benzoate sc per day. TP injections were given at 1600 hr, and plasma samples were obtained at 0800 hr (352 samples). Individual males had widely different behavioral thresholds from 50 μg up to 3.2 mg TP per day. Males showed two types of response: A, a graded increase in ejaculatory activity as plasma testosterone values increased, and B, an all-or-none type of response in which there were ho further increases in ejaculation with increasing plasma levels once the behavioral threshold had been reached. At levels below the physiological range, small changes in plasma testosterone were associated with marked changes in behavior. The female partner exerted a pronounced effect upon the responses of males to TP treatment.     

Sexual behaviour and paternity in three captive groups of rhesus monkeys (Macaca mulatta)

Each offspring born into three captive groups of rhesus monkeys (Macaca mulatta) during the spring of 1981 was assigned (1) a most probable behavioural father and (2) a subset of all possible behavioural fathers, on the basis of intensive observations of sexual activity during the 1980 fall breeding season. These predictions were then compared with true paternity determined by electrophoretic and serological analyses of polymorphic blood proteins of mothers, infants, and all adult and subadult males. Coincidence between the assignments of paternity based upon behavioural and biochemical data occurred no more frequently than chance would allow. Furthermore, there were no significant relationships between biochemical and behavioural rankings of overall reproductive success. It was concluded that conventional estimates of sexual activity during the breeding season are not a reliable indicator of true paternity and relative reproductive success in rhesus macaques.     

The relationship between aggressive behavior and menstrual cycle stage in female rhesus monkeys (Macaca mulatta)

The aggressive behavior of eight adult female rhesus monkeys, living in a captive social group, was studied prior to and during a breeding season extended by vasectomizing all the adult males in the group. Female reproductive status was ascertained by: recording all adult female-adult male copulations, detecting menstruation by vaginal swabbing, and analyzing serum progesterone levels by radioimmunoassay. Females were more aggressive during the follicular stage of their menstrual cycle than the luteal stage or during the period prior to the onset of seasonal ovarian activity. Increases in aggression were limited to increases in the milder forms of agonistic behavior, primarily threatening gestures. Although the females showed their highest rates of noncontact aggressive response categories during the follicular stage, several showed highest rates of contact aggressive response categories in the precycling period.     

Social relations between fathers and offspring in a captive group of rhesus monkeys (Macaca mulatta)

Analysis of social relations between adult males and immatures of known paternity in a captive group of rhesus monkeys (Macaca mulatta) revealed that fathers and offspring associated significantly more than other male-immature dyads. This association was highly variable, however, and there was no evidence of active preference for or investment in offspring by fathers. The tendency of offspring to approach fathers more often than other males appeared to account for the pattern of selective association. Preferential father-offspring association occurred whether or not mothers were in proximity to fathers, but mothers' associations with males did predict their offspring's, especially for the younger juveniles and the infants. It is possible that long-term social relationships between mothers and fathers lead to father-offspring association, but a year-to-year pattern of shifting mating preferences in the group weakens this hypothesis.     

Mother-infant interaction and rank order in Rhesus monkeys (Macaca mulatta)

Our research was made observing 6 infants for a period of 6 months in a group of 13 Macaca Rhesus in captivity conditions. We pointed out that mother-infant body contact behavior in Macaca Rhesus is strictly related to the mothers' rank order. In fact, as the infants of the same age grow up, the higher is the mother's rank order, the more frequent and varied are the infants' interactions with the other members of the group and the more frequently the body contact initiatives are taken by the infants. The behaviors observed in the first months of life can be also considered as the indispensable background of the subjects' future status in the group social structure.     

Aggression within social groups of rhesus monkeys (Macaca mulatta): Effect of contact between groups

Social contact between two groups of rhesus monkeys within tunnel-connected enclosures affected the frequency of aggressive interaction within each group. Contact decreased aggression within the subordinate group but increased it within the dominant group. When the dominance relationship between the two groups was experimentally reversed the effect of contact on intragroup aggression correspondingly reversed.     

Bone marrow and lymphocyte cytogenetics of rhesus monkeys (Macaca mulatta) treated with the clastogen mitomycin C

Rhesus monkeys (Macaca mulatta) were used to determine their effectiveness as experimental animals for different cytogenetic tests with mitomycin C (MC). The micronucleus test (MNT) and/or chromosome analysis of blood and bone marrow were made before and/or after the treatment with mitomycin C. Thus, the controls data and treated data were obtained from the same animals. With the employed methology, the micronucleus test could not be performed on living animals. Less chromosomal damage was detected in the micronucleus test of post-mortem samples than in the chromosome analysis of bone marrow. No influence by the mutagen could be observed in lymphocyte chromosomes at any of the different times of analysis. In contrast to this, bone-marrow chromosomes seemed to be highly affected by mitomycin C at day 1, 2 and 3 after injection. However, before treatment and at day 14, 16 and 17 after treatment there was no visible increase in chromosomal aberration in bone marrow.     

Directional freezing as an alternative method for cryopreserving rhesus macaque (Macaca mulatta) sperm

The objective was to develop a freezing protocol using a directional freezing (DF) technique for cryopreservation of rhesus macaque sperm and achieve a survival rate comparable to that achieved with a conventional freezing (CF) technique. Rhesus macaque sperm frozen with a DF technique, with cooling rates of 12 or 16 °C/min, had higher post-thaw motility (P < 0.05) than those cooled at 7 °C/min (59.3, 61.1, and 50.3%, respectively). Furthermore, sperm cryopreserved with 5% glycerol and a DF technique had similar frozen-thawed sperm motility to those cryopreserved by a CF technique (63.7 vs. 53.9%, P > 0.05). The function of sperm cryopreserved at the optimized cooling rate using a DF technique was evaluated by in vitro fertilization of oocytes collected from gonadotropin-stimulated rhesus macaques. Of the 38 mature oocytes collected, 78.9% were fertilized and 71.1, 47.4, and 42.1% of the oocytes developed to the 2-cell, morulae, and blastocyst stages, respectively. In conclusion, rhesus macaque sperm was effectively cryopreserved using a DF technique, providing a new and effective method for genetic preservation in this important species.     

Germline repertoire of the immunoglobulin V H 3 family in rhesus monkeys

 To facilitate molecular studies of antibody responses in rhesus monkeys (Macaca mulatta), we cloned and sequenced germline segments from its largest and most diverse immunoglobulin heavy-chain gene family, V _H 3. Using a PCR-based approach, we characterized 29 sequences, 20 with open reading frames (ORFs) and 9 pseudogenes. The leader sequences, introns, exons, and recombination signal sequences of M. mulatta V _H 3 gene segments are not strictly identical to those of humans, but the mature coding regions demonstrate, on average, greater than 90% sequence similarity. Although the framework regions are more highly conserved, the complementarity-determining regions (CDRs) also show strong similarities, and their predicted three-dimensional structures resemble those of their human homologues. In one instance, homologous macaque and human CDR1 sequences were 100% identical at the nucleotide level, and some CDR2s shared nucleotide identity as high as 96.5%. However, some rhesus V _H 3 ORFs have unusual structural features, including atypical CDR lengths and uncommon amino acids at structurally crucial positions. The similarity of rhesus and human V _H 3 homologues reinforces the notion that humoral immunity in this nonhuman primate species is an appropriate system for modeling human antibody responses. Received: 10 August 1999 / Revised: 30 December 1999     

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

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.     

Dose—response relationship for X-ray-induced reciprocal translocations in stem-cell spermatogonia of the rhesus monkey (Macaca mulatta)

The induction of reciprocal translocation in stem-cell spermatogonia of the rhesus monkey (Macaca mulatta) was studied after testicular X-irradiation of mature males (50, 100 and 200 rad) or whole-body irradiation of young males (200 and 300 rad). After the recovery of the germinal epithelium, cytogenetic analysis was carried out on spermatocytes descended from irradiation spermatogonia. Preparations of C-banded diakinesis-metaphase I were screened for translocation configurations. The frequencies of abberations obtained were 0% at 0 rad, 0.36% at 50% rad, 0.86% at 100 rad, 0.99% at 200 rad and 0.68% at 300 rad, suggesting a humped dose—response relationship. There was no evidence for the contribution of a quadratic component to the yield in the lower dose range. A comparison of these results with those obtained for other mammals by a number on investigators shows that the frequencies of translocations in the rhesus monkey are much lower than those published for most other mammalian species.     

Use of ultrasound for early pregnancy detection in the rhesus and cynomolgus macaque (Macaca mulatta and Macaca fascicularis)

Diagnostic ultrasound provides an accurate method for the detection of early pregnancy and embryonic loss in macaque species. A developing gestational sac (GS) may be observed on gestational day (GD) 14-15 with positive identification on GD 16-18. Visualization of the yolk sac, embryo, and developing heart on GD 21-25 confirms pregnancy. Continuous observations during embryogenesis provide useful information when assessing the teratogenic potential of a variety of agents.