Use of Introduction Enclosures to Integrate Multimale Cohorts into Groups of Female Rhesus Macaques (Macaca mulatta).

Integrating animals into a new group is a challenge for both free-ranging and captive adult male rhesus monkeys (Macaca mulatta), and for females in groups receiving new males. To ensure the genetic viability of the population, however, male transfers must occur in both natural and captive settings. To facilitate the introduction of groups of adult males to adult females, we designed a new enclosure that is attached to the outdoor compound where females are housed. Here we describe the construction of 3 introduction enclosures, their use during 4 introductions of groups of adult males to adult females, a brief comparison of introduction success rates associated with the new introduction enclosures with those of our traditional male introduction method, and a critique by the various groups of staff members working with the new enclosures. Overall, the introduction enclosures benefitted both the macaques and the facility personnel and appear to be a useful enhancement to our process of integrating breeding groups.

Utility of Automated Feeding Data to Detect Social Instability in a Captive Breeding Colony of Rhesus Macaques (Macaca mulatta): A Case Study of Intrafamily Aggression.

Some captive breeding colonies of rhesus macaques live in large outdoor multimale, multifemale social groups. These groups are composed of several matrilineal families, governed by a clear female dominance hierarchy. Aggression within the same or between different matrilineal families due to social instability can result in trauma and mortality. Therefore, a primary management goal is to detect emerging social unrest before the onset of significant fighting and wounding. Accordingly, groups are monitored routinely for changes in dominance and alliance relations as well as for increases in trauma frequency and severity. Decreased food intake is a normal physiologic response to acute stress; therefore, inappetence in key animals or groups of monkeys might be used as an indicator of increased social stress and emerging instability. An incident of intrafamily aggression occurred recently in a breeding group at our facility and resulted in considerable fighting. Because this compound was equipped with an automated feeding system that tracks the caloric intake of individual animals, we retrospectively analyzed feeding data to determine whether significant reduction in caloric consumption occurred prior to the onset of aggression, compared with baseline values. Neither the entire group nor individual families showed any significant differences in total caloric intake between baseline and previous 24 h values; however, the affected family exhibited a 20% reduction in total caloric during the 24 h prior to the aggression. Most notably, the deposed subfamily showed a marked 58% reduction in caloric intake during the prior 24 h, whereas remaining subfamilies showed no significant changes in intake. High-ranking animals of the group, including the α female, ß female, and α male, similarly exhibited marked decreases in caloric intake during that period. These findings indicate that automated feeders can assist management staff with monitoring social stability in breeding colonies of rhesus macaque.

Effect of Chronic Social Stress on Prenatal Transfer of Antitetanus Immunity in Captive Breeding Rhesus Macaques (Macaca mulatta).

Because tetanus can cause significant morbidity and mortality in NHP, colonywide vaccination with tetanus toxoid is recommended for outdoor breeding colonies of rhesus macaques, with primary immunizations commonly given to infants at 6 mo of age followed by booster vaccines every 10 y. Maternal antibodies are thought to offer protective immunity to infants younger than 6 mo. However, historical colony data from the Yerkes National Primate Research Center show a higher incidence of tetanus among infants (≤ 6 mo old) born to subordinate dams. Whether this higher incidence of infantile tetanus is due to a higher incidence of trauma among subordinate animals or is a stress-induced impairment of maternal antibody protection is unknown. Studies in other NHP species suggest that chronic exposure to social stressors interferes with the receptor-mediated transplacental transfer of IgG. Therefore, the primary aim of this study was to determine whether chronic stress associated with social subordination impairs prenatal transfer of antitetanus immunity in breeding female rhesus macaques. Subjects included 26 high- and 26 low-ranking adult female rhesus macaques that were nearly 5 or 10 y after their initial immunization and their nonimmunized infants. We hypothesized that infants born to subordinate dams that were nearly 10 y after immunization would have the lowest infant-to-dam antibody ratios and thus would be at greatest risk for infection. Results revealed no significant intergroup differences in infant antitetanus IgG levels. However, infant-to-dam IgG ratios against tetanus were significantly lower among subordinate animals compared with dominant macaques, after accounting for the number of years since the dam's initial vaccination. In addition, higher maternal hair cortisol levels predicted lower infantto-dam tetanus toxoid IgG ratios. Together, these findings suggest that chronic social stress in female rhesus macaques may hamper the prenatal transfer of antitetanus immunity to offspring.