Parturition in rhesus monkeys (Macaca mulatta)

During five years of birth season fieldwork, we observed two births and three peri-birth instances of behavior of free-ranging rhesus living in Kathmandu, Nepal. These constitute the first two recorded free-ranging rhesus births, and we compare them to the behavior which has been observed in captivity and expected in the wild. The free-ranging parturition behavior was characterized by a general lack of contact with other troop members and by overall inconspicuousness. In the first birth we observed, the troop moved about 70 m up the hill, leaving the laboring female behind on an open hillside. Two males, a female and a juvenile returned and rested about 20 m from the delivering female. During the second delivery, the female stayed with the troop and seemed to participate normally in most troop interactions, although she avoided physical contact with other troop members. We propose that this near-normal behavior may help to assure successful parturition by allowing the female the needed social isolation and inconspicuousness without any loss of troop protection. It may also partly explain why births have not been observed during previous studies. Observations of rhesus parturition behavior reported from studies of captive monkeys and reports from other free-ranging primate studies are compared with our data.     

Skeptical responding in rhesus monkeys (Macaca mulatta)

Signalers that misinform sufficiently open may become devalued as sources of information; however, “skepticism” and any comparison involved in testing reliability entail a cost that involves delays and energy expenditure. Skepticism may be less costly though, if, as a rule, animals are not equally skeptical of the signals of all conspecifics. Animals with the ability to recognize individual conspecifics and to recall past encounters with them may have the capacity to restrict skepticism to subsets of animals that are most likely to benefit from deception. We played tape-recorded alarm calls of high- and low-ranking rhesus monkeys(Macaca mulatta) to their groups in a feeding context once daily over 8 consecutive days at the Yerkes Primate Center Field Station. Over the sequence of playbacks, response was greater to the calls of high-ranking monkeys, adult response patterns were different from those of juveniles, and for adults especially, decline in responsiveness was punctuated by partial resurgences of response. These differences may be the consequence of the adults’ more extensive histories of interaction with group members that, though generally reliable, vary with respect to the potential benefits of deceptive signaling.     

A microagglutination test for blood typing rhesus monkeys, Macaca mulatta

Summary. We have developed a microagglutination test for typing rhesus monkey erythrocytes that is sensitive, accurate and easy to perform. The technique requires only μ1 quantities of antiserum and cells, and agglutination is easily detected using an inverted microscope. An advantage of this technique is that the typing plates can be stored at -70°C without loss of activity. The results of typing over 400 rhesus blood samples with this technique were 95% concordant with results using the standard microtitre agglutination technique. Preliminary results indicate that this test is also adaptable to typing human blood.     

A microagglutination test for blood typing rhesus monkeys, Macaca mulatta

We have developed a microagglutination test for typing rhesus monkey erythrocytes that is sensitive, accurate and easy to perform. The technique requires only microliter quantities of antiserum and cells, and agglutination is easily detected using an inverted microscope. An advantage of this technique is that the typing plates can be stored at -70 degrees C without loss of activity. The results of typing over 400 rhesus blood samples with this technique were 95% concordant with results using the standard microtitre agglutination technique. Preliminary results indicate that this test is also adaptable to typing human blood.     

Feeding tactics in juvenile rhesus monkeys (Macaca mulatta)

In a group of rhesus monkeys, feeding tactics of juveniles were studied in a competitive situation in which food presentation had been modified, and where food was supplied in a feeding trough six times a day. Juvenile offspring of high-ranking mothers remained longer in the feeding area gathering food. In contrast, juvenile offspring of low-ranking mothers went less often to the feeding area, primarily to collect food. Low-ranking juveniles also gathered the food faster than did dominants and used longer feeding bouts. High-ranking juveniles interrupted their feeding more spontaneously than did subordinate ones. Low-ranking juveniles did so more often as a result of avoiding and being startled. Juvenile males entered the feeding area to satisfy their food requirements more often than females, but were also aggressively expelled more than females. No relation was found between age in months of juveniles and any feeding parameters or causes of interruption. Nor were significant differences found between young and old juveniles. Juvenile rhesus appear to use different tactics in accessing food according to their sex and to their mothers' dominance rank.     

Activated coagulation time for rhesus monkeys (Macaca mulatta)

The activated coagulation time test provided a rapid yet accurate measurement of the intrinsic clotting system in rhesus monkey (Macaca mulatta) whole blood. Other advantages of this test included reproducibility, no requirement for control samples, low cost and commercial availability. The mean activated coagulation time value for 60 normal rhesus monkeys was 96 seconds with a range of 77 to 125 seconds. There were no significant differences due to sex, venipuncture site and time of blood collection.     

Estrous behavior of free-ranging rhesus monkeys (Macaca mulatta)

The sexual behavior of a group of free-ranging rhesus monkeys (Macaca mulatta) was studied for 13 consecutive months in an attempt to determine whether or not sexual activity occurred year-round, and the importance of sexual attraction to rhesus monkey social organization.Estrous behavior was seen both inter-menstrually and peri-menstrually, producing a shorter mean estrous cycle length than reported by other workers. New data was gathered on the interrelationships among age, dominance rank, and sexual activity; son-mother and brothersister matings; and sexual favoritism among free-ranging rhesus monkeys.A few females who failed to conceive during the fall breeding season showed cyclic estrous behavior throughout the entire annual cycle. Hypotheses are given as to possible physiological bases for birth season sexual cycles.Several forms of inter-animal bonding, including sexual bonding, are enumerated, and their importance to rhesus monkey social organization discussed.     

Seasonal weight changes in male rhesus monkeys (Macaca mulatta)

Adult male rhesus monkeys lose weight during the breeding season and regain it during the nonbreeding season. The annual pattern of maximum weight gain just prior to the onset of breeding resembles the seasonal “fattening” seen in squirrel monkeys, but the period of weight gain is less discrete. The magnitude of weight change is less in younger males, in that sexually immature males gain weight in both seasons, but significantly less during the breeding season. Females do not lose weight during the breeding season. Post hoc analyses revealed no significant correlations between male testosterone levels, dominance ranks, weights, or weight changes. The heaviest animals as juveniles were predictably the heaviest as adolescents. The timing of seasonal changes in testosterone did not correlate with the timing of changes in weight; weight losses followed the rise in testosterone, and weight gains continued until early in the breeding season after testosterone levels had already begun to rise. It is suggested that seasonal hormonal changes may influence activities in individuals and that changes in the activities of particular group members may alter the activity patterns of other group members. This alteration of activity patterns due to group influences on individuals as well as individual influences on the group may explain why hormonal regulation of seasonal weight appears to be indirect and why individuals (juveniles) experiencing no seasonal hormonal changes nonetheless show differences in activity patterns and seasonal weight changes.     

Kinship,association, and social relationships in rhesus monkeys (Macaca mulatta)

Data on social interactions with matrilineal kin were collected from two groups of rhesus monkeys for 6 years. All behavioral states, including time within one meter of another, involved kin more often than would be expected by chance. Significant associations were also found between kinship and the frequencies of various forms of agonistic as well as affiliative acts. Frequency of social interaction, however, was not a simple function of time in proximity. Although animals spent more time with kin than nonkin they had more aggressive interactions with kin. Moreover, aggression was biased toward the more serious forms of expression in interactions with kin. Time spent in association was neither predictive of the rate of aggressive interaction nor reduced by high rates of aggressive interaction. Rather than association time influencing rates of interaction, association time may be the consequence of a history of aggressive and affiliative exchanges. Preferential association and high rates of aggressive interaction with kin may be possible due to the existence of compensating social mechanisms nullifying the negative influence of specific aggressive encounters. © 1993 Wiley-Liss, Inc.     

Patterns of affiliation among immature rhesus monkeys (Macaca mulatta)

The affiliative interaction patterns of the immature members of a group of rhesus monkeys at the Yerkes Regional Primate Research Center reflected a strong bias toward matrilineal kin, although this effect was modified by age and sex variables. Association with kin decreased with age, particularly for males. Juvenile males showed less of a kin bias in their behavior than did juvenile females, especially for grooming. Juvenile males also exhibited a preference for interaction with other males. The diminished association with kin and the same-sex bias may be reinforced in adolescence as adult males begin to aggressively target adolescent males involved in agonistic encounters with females or immatures. Adolescent males did not decrease their levels of social interaction relative to those of adolescent females; however, these males preferentially associated with other males (predominantly their own age-sex class) and specifically avoided females and younger animals, both kin and nonkin. Avoidance may diminish conflicts with females or immatures which could result from association, thereby decreasing the potential for selective aggressive interference by adult males. Juvenile and adolescent females maintained strong ties with their kin and preferentially associated with other females and immatures. The breadth of interaction of females with other females may facilitate the establishment of dominance relationships as females mature. Familiarity and predictability may also decrease the necessity of more severe agonistic interaction.